51. |
- Edin, Benoni B, et al.
(författare)
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Finger movement responses of cutaneous mechanoreceptors in the dorsal skin of the human hand.
- 1991
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Ingår i: Journal of Neurophysiology. - 0022-3077 .- 1522-1598. ; 65:3, s. 657-670
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Tidskriftsartikel (refereegranskat)abstract
- 1. The movement sensitivity of dorsal skin mechanoreceptors in the human hand was studied by the use of single afferent recording techniques. 2. Units were classified as slowly (SA) and fast adapting (FA) and further characterized by thresholds to vertical indentation and by receptive-field sizes. Whereas SA units were evenly distributed within the supply area of the superficial branch of the radial nerve. FA units were usually situated near joints. 3. The proportion of different receptor types (32% SAI, 32% SAII, 28% FAI, 8% FAII; n = 107) compared favorably with previous electrophysiological and anatomic data, arguing for minimal sampling bias. The majority of the skin mechanoreceptive units were SA, largely due to a relative scarcity of FAII [Pacinian corpuscles (PC)] units. 4. A large majority (92%) of the afferents responded to active hand or finger movements. Responses in all unit types were consistent with observed movement-induced deformations of their receptive fields. 5. FAI units responded bidirectionally, albeit usually with somewhat higher discharge frequencies for finger flexion, which in most cases were associated with skin stretch. FAI units showed meager responses to remote stimuli, typically responding to one or, at the most, two adjacent joints. 6. SA units typically showed simple directional responses to joint movements with an increased discharge during flexion and a reduced discharge during extension. Joint movement that influenced the skin within the receptive field of SA units elicited graded responses even if the field, as assessed by perpendicular indentations, was minute. This finding suggests that definition of cutaneous receptive fields by classical perpendicular indentations may be inappropriate for the receptors in the hairy, nonglabrous skin. 7. The interpretation of the data from these recordings suggests that cutaneous mechanoreceptors in the dorsal skin can provide the CNS with detailed kinematic information, at least for movements of the hand.
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52. |
- Edin, Benoni B, et al.
(författare)
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Muscle afferent responses to isometric contractions and relaxations in humans.
- 1990
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Ingår i: Journal of Neurophysiology. - 0022-3077 .- 1522-1598. ; 63:6, s. 1307-1313
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Tidskriftsartikel (refereegranskat)abstract
- 1. One hundred and two single afferents from the finger extensor muscles of humans were studied with the microneurography technique. 2. The afferents were provisionally classified as primary muscle spindle afferents (62/102), secondary spindle afferents (22), and Golgi tendon organ afferents (18) on the basis of their responses to four tests: 1) ramp-and-hold stretch, 2) 20- and 50-Hz small-amplitude sinusoidal stretch superimposed on ramp-and-hold stretch, 3) maximal isometric twitch contraction, and 4) stretch sensitization. 3. The response profiles of the three unit types were analyzed during slowly rising isometric contraction terminating with an abrupt relaxation. About 75% (61/84) of all muscle spindle afferents increased their discharge during isometric contraction, whereas the discharge was reduced for the remaining afferents. All Golgi tendon organs increased their discharge during the contraction. 4. The level of extrafusal contraction at which a spindle afferent increased its discharge rate often varied from trial to trial, speaking against a fixed fusimotor recruitment level of the individual spindle ending. 5. In 70% of the spindle afferents, a distinct burst of impulses appeared when the subject rapidly relaxed after the isometric contraction. The burst was more common and usually much more prominent with primary than secondary afferents, often reaching instantaneous discharge rates well above 100 Hz. 6. Whereas all Golgi tendon organ afferents displayed an increased discharge during the contraction phase, only one of them exhibited a rate acceleration close to the relaxation phase. However, this response could clearly be identified as being of different nature than the spindle bursts.(ABSTRACT TRUNCATED AT 250 WORDS)
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53. |
- Edin, Benoni B
(författare)
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Quantitative analysis of static strain sensitivity in human mechanoreceptors from hairy skin.
- 1992
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Ingår i: Journal of Neurophysiology. - 0022-3077 .- 1522-1598. ; 67:5, s. 1105-1113
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Tidskriftsartikel (refereegranskat)abstract
- 1. Microelectrode recordings from 15 slowly adapting (SA) cutaneous mechanoreceptor afferents originating in hairy skin were obtained from the radial nerve in humans. 2. Controlled skin stretch was applied to the back of the hand that encompassed the physiological range of skin stretch during movements at the metacarpophalangeal (MCP) joints. 3. Both SA Group I and II afferents showed exquisite dynamic and static sensitivity to skin stretch. The median static strain sensitivity was 1.0 imp.s-1 per percent skin stretch for SAI units and 1.8 for SAII units. 4. Translated into sensitivity to movements at the MCP joint, both SAI and SAII afferents in the skin of the back of the hand displayed a positional sensitivity that was comparable with that reported for muscle spindle afferents. 5. These data give quantitative support to suggestions that skin receptors in the human hairy skin provide information on nearby joint configurations and therefore may play a specific role in proprioception, kinesthesia, and motor control.
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54. |
- Edin, Benoni
(författare)
-
Quantitative analyses of dynamic strain sensitivity in human skin mechanoreceptors.
- 2004
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 92:6, s. 3233-43
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Tidskriftsartikel (refereegranskat)abstract
- Microneurographical recordings from 24 slowly adapting (SA) and 16 fast adapting (FA) cutaneous mechanoreceptor afferents were obtained in the human radial nerve. Most of the afferents innervated the hairy skin on the back of the hand. The afferents' receptive fields were subjected to controlled strains in a ramp-and-hold fashion with strain velocities from 1 to 64%.s(-1), i.e., strain velocities within most of the physiological range. For all unit types, the mean variation in response onset approached 1 ms for strain velocities >8%.s(-1). Except at the highest strain velocities, the first spike in a typical SAIII unit was evoked at strains <0.5% and a typical SAII unit began to discharge at <1% skin strain. Skin strain velocity had a profound effect on the discharge rates of all classes of afferents. The "typical" peak discharge rate at the highest strain velocity studied was 50-95 imp/s(-1) depending on unit type. Excellent fits were obtained for both SA and FA units when their responses to ramp stretches were modeled by simple power functions (r2 > 0.9 for 95% of the units). SAIII units grouped with SAII with respect to onset latency and onset variation but with SAI units with respect to dynamic strain sensitivity. Because both SA and FA skin afferents respond strongly, quickly, and accurately to skin strain changes, they all seem to be able to provide useful information about movement-related skin strain changes and therefore contribute to proprioception and kinesthesia.
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55. |
- Ehrsson, HH, et al.
(författare)
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Cortical activity in precision- versus power-grip tasks: an fMRI study
- 2000
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 83:1, s. 528-536
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Tidskriftsartikel (refereegranskat)abstract
- Most manual grips can be divided in precision and power grips on the basis of phylogenetic and functional considerations. We used functional magnetic resonance imaging to compare human brain activity during force production by the right hand when subjects used a precision grip and a power grip. During the precision-grip task, subjects applied fine grip forces between the tips of the index finger and the thumb. During the power-grip task, subjects squeezed a cylindrical object using all digits in a palmar opposition grasp. The activity recorded in the primary sensory and motor cortex contralateral to the operating hand was higher when the power grip was applied than when subjects applied force with a precision grip. In contrast, the activity in the ipsilateral ventral premotor area, the rostral cingulate motor area, and at several locations in the posterior parietal and prefrontal cortices was stronger while making the precision grip than during the power grip. The power grip was associated predominately with contralateral left-sided activity, whereas the precision-grip task involved extensive activations in both hemispheres. Thus our findings indicate that in addition to the primary motor cortex, premotor and parietal areas are important for control of fingertip forces during precision grip. Moreover, the ipsilateral hemisphere appears to be strongly engaged in the control of precision-grip tasks performed with the right hand.
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56. |
- Ehrsson, HH, et al.
(författare)
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Differential fronto-parietal activation depending on force used in a precision grip task: an fMRI study
- 2001
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 85:6, s. 2613-2623
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Tidskriftsartikel (refereegranskat)abstract
- Recent functional magnetic resonance imaging (fMRI) studies suggest that the control of fingertip forces between the index finger and the thumb (precision grips) is dependent on bilateral frontal and parietal regions in addition to the primary motor cortex contralateral to the grasping hand. Here we use fMRI to examine the hypothesis that some of the areas of the brain associated with precision grips are more strongly engaged when subjects generate small grip forces than when they employ large grip forces. Subjects grasped a stationary object using a precision grip and employed a small force (3.8 N) that was representative of the forces that are typically used when manipulating small objects with precision grips in everyday situations or a large force (16.6 N) that represents a somewhat excessive force compared with normal everyday usage. Both force conditions involved the generation of time-variant static and dynamic grip forces under isometric conditions guided by auditory and tactile cues. The main finding was that we observed stronger activity in the bilateral cortex lining the inferior part of the precentral sulcus (area 44/ventral premotor cortex), the rostral cingulate motor area, and the right intraparietal cortex when subjects applied a small force in comparison to when they generated a larger force. This observation suggests that secondary sensorimotor related areas in the frontal and parietal lobes play an important role in the control of fine precision grip forces in the range typically used for the manipulation of small objects.
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57. |
- Ehrsson, H Henrik, et al.
(författare)
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Evidence for the involvement of the posterior parietal cortex in coordination of fingertip forces for grasp stability in manipulation
- 2003
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 90:5, s. 2978-2986
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Tidskriftsartikel (refereegranskat)abstract
- Grasp stability during object manipulation is achieved by the grip forces applied normal to the grasped surfaces increasing and decreasing in phase with increases and decreases of destabilizing load forces applied tangential to the grasped surfaces. This force coordination requires that the CNS anticipates the grip forces that match the requirements imposed by the self-generated load forces. Here, we use functional MRI (fMRI) to study neural correlates of the grip-load force coordination in a grip-load force task in which six healthy humans attempted to lift an immovable test object held between the tips of the right index finger and thumb. The recorded brain activity was compared with the brain activity obtained in two control tasks in which the same pair of digits generated forces with similar time courses and magnitudes; i.e., a grip force task where the subjects only pinched the object and did not apply load forces, and a load force task, in which the subjects applied vertical forces to the object without generating grip forces. Thus neither the load force task nor the grip force task involved coordinated grip-load forces, but together they involved the same grip force and load force output. We found that the grip-load force task was specifically associated with activation of a section of the right intraparietal cortex, which is the first evidence for involvement of the posterior parietal cortex in the sensorimotor control of coordinated grip and load forces in manipulation. We suggest that this area might represents a node in the network of cortical and subcortical regions that implement anticipatory control of fingertip forces for grasp stability.
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58. |
- Ehrsson, HH, et al.
(författare)
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Holding an object: neural activity associated with fingertip force adjustments to external perturbations
- 2007
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 97:2, s. 1342-1352
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Tidskriftsartikel (refereegranskat)abstract
- When you hold an object, a sudden unexpected perturbation can threaten the stability of your grasp. In such situations grasp stability is maintained by fast reflexive-like grip-force responses triggered by the somatosensory feedback. Here we use functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms involved in the grip-force responses associated with unexpected increases (loading) and decreases (unloading) in the load force. Healthy right-handed subjects held an instrumented object (of mass 200 g) between the tips of right index finger and thumb. At some time during an interval of 8 to 45 s the weight of the object was suddenly increased or decreased by 90 g. We analyzed the transient increases in the fMRI signal that corresponded precisely in time to these grip-force responses. Activity in the left primary motor cortex was associated with the loading response, but not with unloading, suggesting that sensorimotor processing in this area mediates the sensory-triggered reflexive increase in grip force during loading. Both the loading and the unloading events activated the cingulate motor area and the medial cerebellum. We suggest that these regions could participate in the updating of the sensorimotor representations of the fingertip forces. Finally, the supplementary somatosensory area located on the medial wall of the parietal lobe showed an increase in activity only during unloading, indicating that this area is involved in the sensorimotor processing generating the unloading response. Taken together, our findings suggest different central mechanisms for the grip-force responses during loading and unloading.
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59. |
- Ehrsson, HH, et al.
(författare)
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Imagery of voluntary movement of fingers, toes, and tongue activates corresponding body-part-specific motor representations
- 2003
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 90:5, s. 3304-3316
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Tidskriftsartikel (refereegranskat)abstract
- We investigate whether imagery of voluntary movements of different body parts activates somatotopical sections of the human motor cortices. We used functional magnetic resonance imaging to detect the cortical activity when 7 healthy subjects imagine performing repetitive (0.5-Hz) flexion/extension movements of the right fingers or right toes, or horizontal movements of the tongue. We also collected functional images when the subjects actually executed these movements and used these data to define somatotopical representations in the motor areas. In this study, we relate the functional activation maps to cytoarchitectural population maps of areas 4a, 4p, and 6 in the same standard anatomical space. The important novel findings are 1) that imagery of hand movements specifically activates the hand sections of the contralateral primary motor cortex (area 4a) and the contralateral dorsal premotor cortex (area 6) and a hand representation located in the caudal cingulate motor area and the most ventral part of the supplementary motor area; 2) that when imagining making foot movements, the foot zones of the posterior part of the contralateral supplementary motor area (area 6) and the contralateral primary motor cortex (area 4a) are active; and 3) that imagery of tongue movements activates the tongue region of the primary motor cortex and the premotor cortex bilaterally (areas 4a, 4p, and 6). These results demonstrate that imagery of action engages the somatotopically organized sections of the primary motor cortex in a systematic manner as well as activating some body-part-specific representations in the nonprimary motor areas. Thus the content of the mental motor image, in this case the body part, is reflected in the pattern of motor cortical activation.
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60. |
- Ekeberg, Örjan, et al.
(författare)
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Computer simulation of stepping in the hind legs of the cat : An examination of mechanisms regulating the stance-to-swing transition
- 2005
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 94:6, s. 4256-4268
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Tidskriftsartikel (refereegranskat)abstract
- Physiological studies in walking cats have indicated that two sensory signals are involved in terminating stance in the hind legs: one related to unloading of the leg and the other to hip extension. To study the relative importance of these two signals, we developed a three- dimensional computer simulation of the cat hind legs in which the timing of the swing- to- stance transition was controlled by signals related to the force in ankle extensor muscles, the angle at the hip joint, or a combination of both. Even in the absence of direct coupling between the controllers for each leg, stable stepping was easily obtained using either a combination of ankle force and hip position signals or the ankle force signal alone. Stable walking did not occur when the hip position signal was used alone. Coupling the two controllers by mutual inhibition restored stability, but it did not restore the correct timing of stepping of the two hind legs. Small perturbations applied during the swing phase altered the movement of the contralateral leg in a manner that tended to maintain alternating stepping when the ankle force signal was included but tended to shift coordination away from alternating when the hip position signal was used alone. We conclude that coordination of stepping of the hind legs depends critically on load- sensitive signals from each leg and that mechanical linkages between the legs, mediated by these signals, play a significant role in establishing the alternating gait.
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61. |
- ElManira, A, et al.
(författare)
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Calcium channel subtypes in lamprey sensory and motor neurons
- 1997
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 78:3, s. 1334-1340
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Tidskriftsartikel (refereegranskat)abstract
- El Manira, A. and N. Bussières. Calcium channel subtypes in lamprey sensory and motor neurons. J. Neurophysiol. 78: 1334–1340, 1997. Pharmacologically distinct calcium channels have been characterized in dissociated cutaneous sensory neurons and motoneurons of the larval lamprey spinal cord. To enable cell identification, sensory dorsal cells and motoneurons were selectively labeled with fluorescein-coupled dextran amine in the intact spinal cord in vitro before dissociation. Calcium channels present in sensory dorsal cells, motoneurons, and other spinal cord neurons were characterized with the use of whole cell voltage-clamp recordings and specific calcium channel agonist and antagonists. The results show that a transient low-voltage-activated (LVA) calcium current was present in a proportion of sensory dorsal cells but not in motoneurons, whereas high-voltage-activated (HVA) calcium currents were seen in all neurons recorded. The different components of HVA current were dissected pharmacologically and similar results were obtained for both dorsal cells and motoneurons. The N-type calcium channel antagonist ω-conotoxin-GVIA(ω-CgTx) blocked >70% of the HVA current. A large part of the ω-CgTx block was reversed after washout of the toxin. The L-type calcium channel antagonist nimodipine blocked ∼15% of the total HVA current. The dihydropyridine agonist (±)-BayK 8644 markedly increased the amplitude of the calcium channel current. The BayK-potentiated current was not affected by ω-CgTx, indicating that the reversibility of the ω-CgTx effect is not due to a blockade of L-type channels. Simultaneous application of ω-CgTx and nimodipine left ∼15% of the HVA calcium channel current, a small part of which was blocked by the P/Q-type channel antagonist ω-agatoxin-IVA. In the presence of the three antagonists, the persistent residual current (∼10%) was completely blocked by cadmium. Our results provide evidence for the existence of HVA calcium channels of the N, L, and P/Q types and other HVA calcium channels in lamprey sensory neurons and motoneurons. In addition, certain types of neurons express LVA calcium channels.
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62. |
- Enander, Jonas M.D., et al.
(författare)
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A model for self-organization of sensorimotor function : spinal interneuronal integration
- 2022
-
Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 127:6, s. 1478-1495
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Tidskriftsartikel (refereegranskat)abstract
- Control of musculoskeletal systems depends on integration of voluntary commands and somatosensory feedback in the complex neural circuits of the spinal cord. It has been suggested that the various connectivity patterns that have been identified experimentally may result from the many transcriptional types that have been observed in spinal interneurons. We ask instead whether the muscle-specific details of observed connectivity patterns can arise as a consequence of Hebbian adaptation during early development, rather than being genetically ordained. We constructed an anatomically simplified model musculoskeletal system with realistic muscles and sensors and connected it to a recurrent, random neuronal network consisting of both excitatory and inhibitory neurons endowed with Hebbian learning rules. We then generated a wide set of randomized muscle twitches typical of those described during fetal development and allowed the network to learn. Multiple simulations consistently resulted in diverse and stable patterns of activity and connectivity that included subsets of the interneurons that were similar to “archetypical” interneurons described in the literature. We also found that such learning led to an increased degree of cooperativity between interneurons when performing larger limb movements on which it had not been trained. Hebbian learning gives rise to rich sets of diverse interneurons whose connectivity reflects the mechanical properties of the system. At least some of the transcriptomic diversity may reflect the effects of this process rather than the cause of the connectivity. Such a learning process seems better suited to respond to the musculoskeletal mutations that underlie the evolution of new species. NEW & NOTEWORTHY We present a model of a self-organizing early spinal cord circuitry, which is attached to a biologically realistic sensorized musculoskeletal system. Without any a priori-defined connectivity or organization, learning induced by spontaneous, fetal-like motor activity results in the emergence of a well-functioning spinal interneuronal circuit whose connectivity patterns resemble in many respects those observed in the adult mammalian spinal cord. Hence, our result questions the importance of genetically controlled wiring for spinal cord function.
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63. |
- Enander, Jonas M.D., et al.
(författare)
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A model for self-organization of sensorimotor function : The spinal monosynaptic loop
- 2022
-
Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 127:6, s. 1460-1477
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Tidskriftsartikel (refereegranskat)abstract
- Recent spinal cord literature abounds with descriptions of genetic preprogramming and the molecular control of circuit formation. In this paper, we explore to what extent circuit formation based on learning rather than preprogramming could explain the selective formation of the monosynaptic projections between muscle spindle primary afferents and homonymous motoneurons. We adjusted the initially randomized gains in the neural network according to a Hebbian plasticity rule while exercising the model system with spontaneous muscle activity patterns similar to those observed during early fetal development. Normal connectivity patterns developed only when we modeled b motoneurons, which are known to innervate both intrafusal and extrafusal muscle fibers in vertebrate muscles but were not considered in previous literature regarding selective formation of these synapses in animals with paralyzed muscles. It was also helpful to correctly model the greatly reduced contractility of extrafusal muscle fibers during early development. Stronger and more coordinated muscle activity patterns such as observed later during neonatal locomotion impaired projection selectivity. These findings imply a generic functionality of a musculoskeletal system to imprint important aspects of its mechanical dynamics onto a neural network, without specific preprogramming other than setting a critical period for the formation and maturation of this general pattern of connectivity. Such functionality would facilitate the successful evolution of new species with altered musculoskeletal anatomy, and it may help to explain patterns of connectivity and associated reflexes that appear during abnormal development. NEW & NOTEWORTHY A novel model of self-organization of early spinal circuitry based on a biologically realistic plant, sensors, and neuronal plasticity in conjunction with empirical observations of fetal development. Without explicit need for guiding genetic rules, connection matrices emerge that support functional self-organization of the mature pattern of Ia to motoneuron connectivity in the spinal circuitry.
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64. |
- Endo, T, et al.
(författare)
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Asymmetric operation of the locomotor central pattern generator in the neonatal mouse spinal cord
- 2008
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 100:6, s. 3043-3054
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Tidskriftsartikel (refereegranskat)abstract
- The rhythmic voltage oscillations in motor neurons (MNs) during locomotor movements reflect the operation of the pre-MN central pattern generator (CPG) network. Recordings from MNs can thus be used as a method to deduct the organization of CPGs. Here, we use continuous conductance measurements and decomposition methods to quantitatively assess the weighting and phase tuning of synaptic inputs to different flexor and extensor MNs during locomotor-like activity in the isolated neonatal mice lumbar spinal cord preparation. Whole cell recordings were obtained from 22 flexor and 18 extensor MNs in rostral and caudal lumbar segments. In all flexor and the large majority of extensor MNs the extracted excitatory and inhibitory synaptic conductances alternate but with a predominance of inhibitory conductances, most pronounced in extensors. These conductance changes are consistent with a “push–pull” operation of locomotor CPG. The extracted excitatory and inhibitory synaptic conductances varied between 2 and 56% of the mean total conductance. Analysis of the phase tuning of the extracted synaptic conductances in flexor and extensor MNs in the rostral lumbar cord showed that the flexor-phase–related synaptic conductance changes have sharper locomotor-phase tuning than the extensor-phase–related conductances, suggesting a modular organization of premotor CPG networks consisting of reciprocally coupled, but differently composed, flexor and extensor CPG networks. There was a clear difference between phase tuning in rostral and caudal MNs, suggesting a distinct operation of CPG networks in different lumbar segments. The highly asymmetric features were preserved throughout all ranges of locomotor frequencies investigated and with different combinations of locomotor-inducing drugs. The asymmetric nature of CPG operation and phase tuning of the conductance profiles provide important clues to the organization of the rodent locomotor CPG and are compatible with a multilayered and distributed structure of the network.
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65. |
- Ericson, Mia, 1970, et al.
(författare)
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Acute ethanol exposure elevates muscarinic tone in the septohippocampal system.
- 2009
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 103:1, s. 290-296
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Tidskriftsartikel (refereegranskat)abstract
- The septohippocampal system has been implicated in the cognitive deficits associated with ethanol consumption, but the cellular basis of ethanol action awaits full elucidation. In the MS/DB, a muscarinic tone, reflective of firing activity of resident cholinergic neurons, regulates that of their non-cholinergic, putatively GABAergic, counterparts. Here we tested the hypothesis that ethanol alters this muscarinic tone. The spontaneous firing activity of cholinergic and non-cholinergic MS/DB neurons were monitored in acute MS/DB slices from C57Bl/6 mice. Exposing the entire slice to ethanol increased firing in both cholinergic and non-cholinergic neurons. However, applying ethanol focally to individual MS/DB neurons increased firing only in cholinergic neurons. The differential outcome suggested different mechanisms of ethanol action on cholinergic and non-cholinergic neurons. Indeed, with bath-perfused ethanol, the muscarinic antagonist methyl scopolamine prevented the increase in firing in non-cholinergic, but not cholinergic, MS/DB neurons. Thus, the effect on non-cholinergic neuronal firing was secondary to ethanol's direct action of acutely increasing muscarinic tone. We propose that the acute ethanol-induced elevation of muscarinic tone in the MS/DB contributes to the altered net flow of neuronal activity in the septohippocampal system that underlies compromised cognitive function.
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66. |
- Fagergren, Anders, et al.
(författare)
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Control strategies correcting inaccurately programmed fingertip forces : Model predictions derived from human behavior
- 2003
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 89:6, s. 2904-2916
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Tidskriftsartikel (refereegranskat)abstract
- When picking up a familiar object between the index finger and the thumb, the motor commands are predetermined by the CNS to correspond to the frictional demand of the finger-object contact area. If the friction is less than expected, the object will start to slip out of the hand, giving rise to unexpected sensory information. Here we study the correction strategies of the motor system in response to an unexpected frictional demand. The motor commands to the mononeuron pool are estimated by a novel technique combining behavioral recordings and neuromuscular modelling. We first propose a mathematical model incorporating muscles, hand mechanics, and the action of lifting an object. A simple control system sends motor commands to and receives sensory signals from the model. We identify three factors influencing the efficiency of the correction: the time development of the motor command, the delay between the onset of the grip and load forces (GF-LF-delay), and how fast the lift is performed. A sensitivity analysis describes how these factors affect the ability to prevent or stop slipping and suggests an efficient control strategy that prepares and corrects for an altered frictional condition. We then analyzed fingertip grip and load forces (GF and LF) and position data from 200 lifts made by five healthy subjects. The friction was occasionally reduced, forcing an increase of the GF to prevent the object being dropped. The data were then analyzed by feeding it through the inverted model. This provided an estimate of the motor commands to the motoneuron pool. As suggested by the sensitivity analysis the GF-LF-delay was indeed used by the subjects to prevent slip. In agreement with recordings from neurons in the primary motor cortex of the monkey, a sharp burst in the estimated GF motor command (NGF) efficiently arrested any slip. The estimated motor commands indicate a control system that uses a small set of corrective commands, which together with the GF-LF-delay form efficient correction strategies. The selection of a strategy depends on the amount of tactile information reporting unexpected friction and how long it takes to arrive. We believe that this technique of estimating the motor commands behind the fingertip forces during a precision grip lift can provide a powerful tool for the investigation of the central control of the motor system.
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67. |
- Fagerstedt, P, et al.
(författare)
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Lateral turns in the Lamprey. I. Patterns of motoneuron activity
- 2001
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 86:5, s. 2246-2256
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Tidskriftsartikel (refereegranskat)abstract
- The activity of motoneurons during lateral turns was studied in a lower vertebrate, the lamprey, to investigate how a supraspinal command for the change of direction during locomotion is transmitted from the brain stem and integrated with the activity of the spinal locomotor pattern generator. Three types of experiments were performed. 1) The muscular activity during lateral turns in freely swimming adult lampreys was recorded by electromyography (EMG). It was characterized by increased cycle duration and increased duration, intensity, and cycle proportion of the bursts on the side toward which the animal turns. 2) Electrical stimulation of the skin on one side of the head in a head-spinal cord preparation of the lamprey during fictive locomotion elicited asymmetric ventral root burst activity with similar characteristics as observed in the EMG of intact lampreys during lateral turns. The cycle duration and ventral root burst intensity, duration, and cycle proportion on the side of the spinal cord contralateral to the stimulus were increased; hence a fictive lateral turn away from the stimulus could be produced. The fictive turn propagated caudally with decreasing amplitude. The increase in burst duration during the turn correlated well with the increase in cycle duration, while changes in contralateral burst intensity and burst duration did not co-vary. Turning responses varied depending on the timing (phase) of the skin stimulation: stimuli in the first two-thirds of a cycle evoked a turn in the same cycle, whereas stimuli in the last third gave a turn in the following cycle. The largest turns were evoked by stimuli in the first third of a cycle. 3) Fictive turns were abolished after transection of the trigeminal nerve or a rhombencephalic midline split, but not in a rhombencephalic preparation with transected cerebellar commissure. High spinal hemisection was sufficient to block turning toward the lesioned side, while turns toward the intact side remained. Taken together these findings suggest that the reticulospinal turn command is essentially unilateral and generated in the rhombencephalon.
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68. |
- Fagerstedt, P, et al.
(författare)
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Lateral turns in the Lamprey. II. Activity of reticulospinal neurons during the generation of fictive turns
- 2001
-
Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 86:5, s. 2257-2265
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Tidskriftsartikel (refereegranskat)abstract
- We studied the neural correlates of turning movements during fictive locomotion in a lamprey in vitro brain–spinal cord preparation. Electrical stimulation of the skin on one side of the head was used to evoke fictive turns. Intracellular recordings were performed from reticulospinal cells in the middle (MRRN) and posterior (PRRN) rhombencephalic reticular nuclei, and from Mauthner cells, to characterize the pattern of activity in these cell groups, and their possible functional role for the generation of turns. All recorded reticulospinal neurons modified their activity during turns. Many cells in both the rostral and the caudal MRRN, and Mauthner cells, were strongly excited during turning. The level of activity of cells in rostral PRRN was lower, while the lowest degree of activation was found in cells in caudal PRRN, suggesting that MRRN may play a more important role for the generation of turning behavior. The sign of the response (i.e., excitation or inhibition) to skin stimulation of a neuron during turns toward (ipsilateral), or away from (contralateral) the side of the cell body was always the same. The cells could thus be divided into four types: 1) cells that were excited during ipsilateral turns and inhibited during contralateral turns; these cells provide an asymmetric excitatory bias to spinal networks and presumably play an important role for the generation of turns; these cells were common ( n = 35; 52%) in both MRRN and PRRN; 2) cells that were excited during turns in either direction; these cells were common ( n = 19; 28%), in particular in MRRN; they could be involved in a general activation of the locomotor system after skin stimulation; some of the cells were also more activated during turns in one direction and could contribute to an asymmetric turn command; 3) one cell that was inhibited during ipsilateral turns and excited during contralateral turns; and 4) cells ( n = 12; 18%) that were inhibited during turns in either direction. In summary, our results show that, in the lamprey, the large majority of reticulospinal cells have responses during lateral turns that are indicative of a causal role for these cells in turn generation. This also suggests a considerable overlap between the command system for lateral turns evoked by skin stimulation, which was studied here, and other reticulospinal command systems, e.g., for lateral turns evoked by other types of stimuli, initiation of locomotion, and turns in the vertical planes.
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69. |
- Falck-Ytter, Terje
(författare)
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Predicting other people's action goals with low-level motor information
- 2012
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 107:11, s. 2923-2925
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Tidskriftsartikel (refereegranskat)abstract
- In support for the direct-matching hypothesis, Ambrosini et al. (2011) recently reported that goal-directed saccades during action observation were modulated by manipulations of basic motor information. This finding indicates that motor programs, activated by low-level visual descriptions of others' actions, are involved in predicting other people's action goals. Here, I put this result into a broader context, review alternative interpretations, and suggest strategies for future studies.
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70. |
- Fardo, F, et al.
(författare)
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Delta and gamma oscillations in operculo-insular cortex underlie innocuous cold thermosensation
- 2017
-
Ingår i: Journal of neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 117:5, s. 1959-1968
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Tidskriftsartikel (refereegranskat)abstract
- Cold-sensitive and nociceptive neural pathways interact to shape the quality and intensity of thermal and pain perception. Yet the central processing of cold thermosensation in the human brain has not been extensively studied. Here, we used magnetoencephalography and EEG in healthy volunteers to investigate the time course (evoked fields and potentials) and oscillatory activity associated with the perception of cold temperature changes. Nonnoxious cold stimuli consisting of Δ3°C and Δ5°C decrements from an adapting temperature of 35°C were delivered on the dorsum of the left hand via a contact thermode. Cold-evoked fields peaked at around 240 and 500 ms, at peak latencies similar to the N1 and P2 cold-evoked potentials. Importantly, cold-related changes in oscillatory power indicated that innocuous thermosensation is mediated by oscillatory activity in the range of delta (1–4 Hz) and gamma (55–90 Hz) rhythms, originating in operculo-insular cortical regions. We suggest that delta rhythms coordinate functional integration between operculo-insular and frontoparietal regions, while gamma rhythms reflect local sensory processing in operculo-insular areas. NEW & NOTEWORTHY Using magnetoencephalography, we identified spatiotemporal features of central cold processing, with respect to the time course, oscillatory profile, and neural generators of cold-evoked responses in healthy human volunteers. Cold thermosensation was associated with low- and high-frequency oscillatory rhythms, both originating in operculo-insular regions. These results support further investigations of central cold processing using magnetoencephalography or EEG and the clinical utility of cold-evoked potentials for neurophysiological assessment of cold-related small-fiber function and damage.
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71. |
- Farina, D, et al.
(författare)
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Discharge variability of motor units in an intrinsic muscle of transplanted hand
- 2008
-
Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 99:5, s. 2232-2240
-
Tidskriftsartikel (refereegranskat)abstract
- The study analyzed the discharge characteristics of the motor units in an intrinsic muscle of a transplanted hand. Multichannel electromyographic (EMG) recordings were obtained in 11 experimental sessions over 16 mo starting from day 205 after a hand was transplanted in a 35-yr-old man who had lost his right hand 22 yr earlier. The action potentials discharged by single motor units were identified from the surface EMG signals of the abductor digiti minimi muscle in the transplanted hand as the individual performed 60-s maximal and linearly increasing (ramp) contractions. Discharge rate decreased from 27.1 ± 8.4 pulses per second (pps) at the start of the maximal contractions to 17.2 ± 2.9 pps at the end ( P < 0.001) and increased from 17.4 ± 4.3 to 22.1 ± 5.0 pps during the ramp contractions ( P < 0.05). The SD of the interspike interval (ISI) nearly related to the mean ISI with a similar regression slope for the maximal (0.49 ± 0.09) and ramp contractions (0.43 ± 0.10). The coefficient of variation for ISI was higher than values in able-bodied persons and did not change during either the maximal (36.8 ± 10.8%) or the ramp contractions (35.9 ± 7.4%). High-frequency bursts of activity with <20 ms between two and six action potentials occurred during both maximal and ramp contractions. In conclusion, motor neurons that reinnervated a muscle in a transplanted hand discharged action potentials with a high degree of variability that suggested greater synaptic noise during the voluntary contractions.
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72. |
- Felix, RA, et al.
(författare)
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Development of on-off spiking in superior paraolivary nucleus neurons of the mouse
- 2013
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 109:11, s. 2691-2704
-
Tidskriftsartikel (refereegranskat)abstract
- The superior paraolivary nucleus (SPON) is a prominent cell group in the auditory brain stem that has been increasingly implicated in representing temporal sound structure. Although SPON neurons selectively respond to acoustic signals important for sound periodicity, the underlying physiological specializations enabling these responses are poorly understood. We used in vitro and in vivo recordings to investigate how SPON neurons develop intrinsic cellular properties that make them well suited for encoding temporal sound features. In addition to their hallmark rebound spiking at the stimulus offset, SPON neurons were characterized by spiking patterns termed onset, adapting, and burst in response to depolarizing stimuli in vitro. Cells with burst spiking had some morphological differences compared with other SPON neurons and were localized to the dorsolateral region of the nucleus. Both membrane and spiking properties underwent strong developmental regulation, becoming more temporally precise with age for both onset and offset spiking. Single-unit recordings obtained in young mice demonstrated that SPON neurons respond with temporally precise onset spiking upon tone stimulation in vivo, in addition to the typical offset spiking. Taken together, the results of the present study demonstrate that SPON neurons develop sharp on-off spiking, which may confer sensitivity to sound amplitude modulations or abrupt sound transients. These findings are consistent with the proposed involvement of the SPON in the processing of temporal sound structure, relevant for encoding communication cues.
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73. |
- Fiath, Richard, et al.
(författare)
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Large-scale recording of thalamocortical circuits : in vivo electrophysiology with the two-dimensional electronic depth control silicon probe
- 2016
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 116:5, s. 2312-2330
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Tidskriftsartikel (refereegranskat)abstract
- Recording simultaneous activity of a large number of neurons in distributed neuronal networks is crucial to understand higher order brain functions. We demonstrate the in vivo performance of a recently developed electrophysiological recording system comprising a two-dimensional, multi-shank, high-density silicon probe with integrated complementary metal-oxide semiconductor electronics. The system implements the concept of electronic depth control (EDC), which enables the electronic selection of a limited number of recording sites on each of the probe shafts. This innovative feature of the system permits simultaneous recording of local field potentials (LFP) and single-and multiple-unit activity (SUA and MUA, respectively) from multiple brain sites with high quality and without the actual physical movement of the probe. To evaluate the in vivo recording capabilities of the EDC probe, we recorded LFP, MUA, and SUA in acute experiments from cortical and thalamic brain areas of anesthetized rats and mice. The advantages of large-scale recording with the EDC probe are illustrated by investigating the spatiotemporal dynamics of pharmacologically induced thalamocortical slow-wave activity in rats and by the two-dimensional tonotopic mapping of the auditory thalamus. In mice, spatial distribution of thalamic responses to optogenetic stimulation of the neocortex was examined. Utilizing the benefits of the EDC system may result in a higher yield of useful data from a single experiment compared with traditional passive multielectrode arrays, and thus in the reduction of animals needed for a research study.
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74. |
- Filingeri, D., et al.
(författare)
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The biology of skin wetness perception and its implications in manual function and for reproducing complex somatosensory signals in neuroprosthetics
- 2017
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 117:4, s. 1761-1775
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Tidskriftsartikel (refereegranskat)abstract
- Our perception of skin wetness is generated readily, yet humans have no known receptor (hygroreceptor) to signal this directly. It is easy to imagine the sensation of water running over our hands or the feel of rain on our skin. The synthetic sensation of wetness is thought to be produced from a combination of specific skin thermal and tactile inputs, registered through thermoreceptors and mechanoreceptors, respectively. The present review explores how thermal and tactile afference from the periphery can generate the percept of wetness centrally. We propose that the main signals include information about skin cooling, signaled primarily by thinly myelinated thermoreceptors, and rapid changes in touch, through fast-conducting, myelinated mechanoreceptors. Potential central sites for integration of these signals, and thus the perception of skin wetness, include the primary and secondary somatosensory cortices and the insula cortex. The interactions underlying these processes can also be modeled to aid in understanding and engineering the mechanisms. Furthermore, we discuss the role that sensing wetness could play in precision grip and the dexterous manipulation of objects. We expand on these lines of inquiry to the application of the knowledge in designing and creating skin sensory feedback in prosthetics. The addition of real-time, complex sensory signals would mark a significant advance in the use and incorporation of prosthetic body parts for amputees in everyday life. NEW & NOTEWORTHY Little is known about the underlying mechanisms that generate the perception of skin wetness. Humans have no specific hygroreceptor, and thus temperature and touch information combine to produce wetness sensations. The present review covers the potential mechanisms leading to the perception of wetness, both peripherally and centrally, along with their implications for manual function. These insights are relevant to inform the design of neuroengineering interfaces, such as sensory prostheses for amputees.
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75. |
- Filipovic, Marko, et al.
(författare)
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Direct pathway neurons in mouse dorsolateral striatum in vivo receive stronger synaptic input than indirect pathway neurons
- 2019
-
Ingår i: Journal of Neurophysiology. - : AMER PHYSIOLOGICAL SOC. - 0022-3077 .- 1522-1598. ; 122:6, s. 2294-2303
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Tidskriftsartikel (refereegranskat)abstract
- Striatal projection neurons, the medium spiny neurons (MSNs), play a crucial role in various motor and cognitive functions. MSNs express either D1- or D2-type dopamine receptors and initiate the direct-pathway (dMSNs) or indirect pathways (iMSNs) of the basal ganglia, respectively. dMSNs have been shown to receive more inhibition than iMSNs from intrastriatal sources. Based on these findings, computational modeling of the suiatal network has predicted that under healthy conditions dMSNs should receive more total input than iMSNs. To test this prediction, we analyzed in vivo whole cell recordings from dMSNs and iMSNs in healthy and dopamine-depleted (60HDA) anaesthetized mice. By comparing their membrane potential fluctuations, we found that dMSNs exhibited considerably larger membrane potential fluctuations over a wide frequency range. Furthermore, by comparing the spike-triggered average membrane potentials. we found that dMSNs depolarized toward the spike threshold significantly faster than iMSNs did. Together, these findings (in particular the STA analysis) corroborate the theoretical prediction that direct-pathway MSNs receive stronger total input than indirect-pathway neurons. Finally, we found that dopamine-depleted mice exhibited no difference between the membrane potential fluctuations of dMSNs and iMSNs. These data provide new insights into the question of how the lack of dopamine may lead to behavioral deficits associated with Parkinson's disease. NEW & NOTEWORTHY The direct and indirect pathways of the basal ganglia originate from the D1- and D2-type dopamine receptor expressing medium spiny neurons (dMSNs and iMSNs). Theoretical results have predicted that dMSNs should receive stronger synaptic input than iMSNs. Using in vivo intracellular membrane potential data, we provide evidence that dMSNs indeed receive stronger input than iMSNs, as has been predicted by the computational model.
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76. |
- Fjell, J, et al.
(författare)
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In vivo NGF deprivation reduces SNS expression and TTX-R sodium currents in IB4-negative DRG neurons
- 1999
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 81:2, s. 803-810
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Tidskriftsartikel (refereegranskat)abstract
- In vivo NGF deprivation reduces SNS expression and TTX-R sodium currents in IB4-negative DRG neurons. Recent evidence suggests that changes in sodium channel expression and localization may be involved in some pathological pain syndromes. SNS, a tetrodotoxin-resistant (TTX-R) sodium channel, is preferentially expressed in small dorsal root ganglion (DRG) neurons, many of which are nociceptive. TTX-R sodium currents and SNS mRNA expression have been shown to be modulated by nerve growth factor (NGF) in vitro and in vivo. To determine whether SNS expression and TTX-R currents in DRG neurons are affected by reduced levels of systemic NGF, we immunized adult rats with NGF, which causes thermal hypoalgesia in rats with high antibody titers to NGF. DRG neurons cultured from rats with high antibody titers to NGF, which do not bind the isolectin IB4 (IB4−) but do express TrkA, were studied with whole cell patch-clamp and in situ hybridization. Mean TTX-R sodium current density was decreased from 504 ± 77 pA/pF to 307 ± 61 pA/pF in control versus NGF-deprived neurons, respectively. In comparison, the mean TTX-sensitive sodium current density was not significantly different between control and NGF-deprived neurons. Quantification of SNS mRNA hybridization signal showed a significant decrease in the signal in NGF-deprived neurons compared with the control neurons. The data suggest that NGF has a major role in the maintenance of steady-state levels of TTX-R sodium currents and SNS mRNA in IB4− DRG neurons in adult rats in vivo.
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77. |
- Flanagan, J Randall, et al.
(författare)
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Gaze behavior when reaching to remembered targets.
- 2008
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 100:3, s. 1533-43
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Tidskriftsartikel (refereegranskat)abstract
- People naturally direct their gaze to visible hand movement goals. Doing so improves reach accuracy through use of signals related to gaze position and visual feedback of the hand. Here, we studied where people naturally look when acting on remembered target locations. Four targets were presented on a screen, in peripheral vision, while participants fixed a central cross (encoding phase). Four seconds later, participants used a pen to mark the remembered locations while free to look wherever they wished (recall phase). Visual references, including the screen and the cross, were present throughout. During recall, participants neither looked at the marked locations nor prevented eye movements. Instead, gaze behavior was erratic and was comprised of gaze shifts loosely coupled in time and space with hand movements. To examine whether eye and hand movements during encoding affected gaze behavior during recall, in additional encoding conditions, participants marked the visible targets with either free gaze or with central cross fixation or just looked at the targets. All encoding conditions yielded similar erratic gaze behavior during recall. Furthermore, encoding mode did not influence recall performance, suggesting that participants, during recall, did not exploit sensorimotor memories related to hand and gaze movements during encoding. Finally, we recorded a similar lose coupling between hand and eye movements during an object manipulation task performed in darkness after participants had viewed the task environment. We conclude that acting on remembered versus visible targets can engage fundamentally different control strategies, with gaze largely decoupled from movement goals during memory-guided actions.
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78. |
- Folmli, Brookes, et al.
(författare)
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Dose-response of somatosensory cortex repeated anodal transcranial direct current stimulation on vibrotactile detection : A randomized sham controlled trial
- 2018
-
Ingår i: Journal of Neurophysiology. - Bethesda, United States : American Physiological Society. - 0022-3077 .- 1522-1598.
-
Tidskriftsartikel (refereegranskat)abstract
- This randomized sham-controlled trial investigated anodal transcranial direct current stimulation (tDCS) over the somatosensory cortex contralateral to hand dominance for dose-response (1mA-20 minutes x 5 days) effects on vibrotactile detection thresholds (VDT). VDT was measured before and after tDCS on days 1,3&5 for low (30hz) and high (200hz) frequency vibrations on the dominant and non-dominant hands in 29 healthy adults (mean age = 22.86; 15 males, 14 females). Only the dominant hand 200Hz VDT displayed statistically significant medium effect size improvement for mixed model analysis of variance time x group interaction for active tDCS compared to sham. Post Hoc contrasts were statistically significant for dominant hand 200Hz VDT on day 5 after tDCS compared to day 1 before tDCS , day 1 after tDCS and day 3 before tDCS. There was a linear dose-response improvement with dominant hand 200Hz VDT mean difference decreasing from day 1 before tDCS peaking at -15.5% (SD=34.9%) on day 5 after tDCS. Both groups showed learning effect trends over time for all VDT test conditions but only the non-dominant hand 30Hz VDT was statistically significant (p=0.03) though Post Hoc contrasts were non-significant after Sidak adjustment. No adverse effects for tDCS were reported. In conclusion, anodal tDCS 1mA-20 minutes x 5 days on the dominant sensory cortex can modulate a linear improvement of dominant hand high frequency VDT but not for low frequency or non-dominant hand VDT.
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79. |
- Franklin, Sae, et al.
(författare)
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Congruent visual cues speed dynamic motor adaptation
- 2023
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 130:2, s. 319-331
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Tidskriftsartikel (refereegranskat)abstract
- Motor adaptation to novel dynamics occurs rapidly using sensed errors to update the current motor memory. This adaption is strongly driven by proprioceptive and visual signals that indicate errors in the motor memory. Here, we extend this previous work by investigating whether the presence of additional visual cues could increase the rate of motor adaptation, specifically when the visual motion cue is congruent with the dynamics. Six groups of participants performed reaching movements while grasping the handle of a robotic manipulandum. A visual cue (small red circle) was connected to the cursor (representing the hand position) via a thin red bar. After a baseline, a unidirectional (3 groups) or bidirectional (3 groups) velocity-dependent force field was applied during the reach. For each group, the movement of the red object relative to the cursor was either congruent with the force field dynamics, incongruent with the force field dynamics, or constant (fixed distance from the cursor). Participants adapted more to the unidirectional force fields than to the bidirectional force field groups. However, across both force fields, groups in which the visual cues matched the type of force field (congruent visual cue) exhibited higher final adaptation level at the end of learning than the control or incongruent conditions. In all groups, we observed that an additional congruent cue assisted the formation of the motor memory of the external dynamics. We then demonstrate that a state estimation-based model that integrates proprioceptive and visual information can successfully replicate the experimental data.NEW & NOTEWORTHY We demonstrate that adaptation to novel dynamics is stronger when additional online visual cues that are congruent with the dynamics are presented during adaptation, compared with either a constant or incongruent visual cue. This effect was found regardless of whether a bidirectional or unidirectional velocity-dependent force field was presented to the participants. We propose that this effect might arise through the inclusion of this additional visual cue information within the state estimation process.
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80. |
- Free, Daniel B., et al.
(författare)
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Essential tremor accentuates the pattern of tremor-band coherence between upper limb muscles
- 2023
-
Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 129:3, s. 524-540
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Tidskriftsartikel (refereegranskat)abstract
- Although essential tremor (ET) is one of the most common movement disorders, current treatment options are relatively limited. Peripheral tremor suppression methods have shown potential, but we do not currently know which muscles are most responsible for patients' tremor, making it difficult to optimize suppression methods. The purpose of this study was to quantify the relation-ships between the tremorogenic activity in muscles throughout the upper limb. Muscle activity was recorded from the 15 major superficial upper limb muscles in 24 subjects with ET while they held various postures or made upper limb movements. We cal-culated the coherence in the tremor band (4-12 Hz) between the activity of all muscle pairs and the time-varying phase differ-ence between sufficiently coherent muscle pairs. Overall, the observed pattern somewhat mirrored functional relationships: agonistic muscle pairs were most coherent and in phase, whereas antagonist and unrelated muscle pairs exhibited less coher-ence and were either consistently in phase, consistently antiphase, consistently out of phase (unrelated pairs only), or else incon-sistent. Patients exhibited significantly more coherence than control subjects (P < 0.001) in the vast majority of muscle pairs (95 of 105). Furthermore, differences between patients and control subjects were most pronounced among agonists; thus, the coher-ence pattern existing in control subjects was accentuated in patients with ET. We conclude that tremor-band activity is broadly distributed among the muscles of the upper limb, challenging efforts to determine which muscles are most responsible for a patient's tremor.
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81. |
- Fridberger, Anders, 1966-, et al.
(författare)
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Loud sound-induced changes in cochlear mechanics
- 2002
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 88:5, s. 2341-2348
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the inner ear response to intense sound and the mechanisms behind temporary threshold shifts, anesthetized guinea pigs were exposed to tones at 100-112 dB SPL. Basilar membrane vibration was measured using laser velocimetry, and the cochlear microphonic potential, compound action potential of the auditory nerve, and local electric AC potentials in the organ of Corti were used as additional indicators of cochlear function. After exposure to a 12-kHz intense tone, basilar membrane vibrations in response to probe tones at the characteristic frequency of the recording location (17 kHz) were transiently reduced. This reduction recovered over the course of 50 ms in most cases. Organ of Corti AC potentials were also reduced and recovered with a time course similar to the basilar membrane. When using a probe tone at either 1 or 4 kHz, organ of Corti AC potentials were unaffected by loud sound, indicating that transducer channels remained intact. In most experiments, both the basilar membrane and the cochlear microphonic response to the 12-kHz overstimulation was constant throughout the duration of the intense stimulus, despite a large loss of cochlear sensitivity. It is concluded that the reduction of basilar membrane velocity that followed loud sound was caused by changes in cochlear amplification and that the cochlear response to intense stimulation is determined by the passive mechanical properties of the inner ear structures.
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82. |
- Gabriel, J. P., et al.
(författare)
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Locomotor pattern in the adult zebrafish spinal cord in vitro
- 2008
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 99:1, s. 37-48
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Tidskriftsartikel (refereegranskat)abstract
- The zebrafish is an attractive model system for studying the function of the spinal locomotor network by combining electrophysiological, imaging, and genetic approaches. Thus far, most studies have been focusing on embryonic and larval stages. In this study we have developed an in vitro preparation of the isolated spinal cord from adult zebrafish in which locomotor activity can be induced while the activity of single neurons can be monitored using whole cell recording techniques. Application of NMDA elicited rhythmic locomotor activity that was monitored by recording from muscles or ventral roots in semi-intact or isolated spinal cord preparations, respectively. This rhythmic activity displayed a left-right alternation and a rostrocaudal delay. Blockade of glycinergic synaptic transmission by strychnine switched the alternating activity into synchronous bursting in the left and right sides as well as along the rostrocaudal axis. Whole cell recordings from motoneurons showed that they receive phasic synaptic inputs that were correlated with the locomotor activity recorded in ventral roots. This newly developed in vitro preparation of the adult zebrafish spinal cord will allow examination of the organization of the spinal locomotor network in an adult system to complement studies in zebrafish larvae and new born rodents.
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83. |
- Gentile, G, et al.
(författare)
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Integration of visual and tactile signals from the hand in the human brain: an FMRI study
- 2011
-
Ingår i: Journal of neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 105:2, s. 910-922
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Tidskriftsartikel (refereegranskat)abstract
- In the non-human primate brain, a number of multisensory areas have been described where individual neurons respond to visual, tactile and bimodal visuotactile stimulation of the upper limb. It has been shown that such bimodal neurons can integrate sensory inputs in a linear or nonlinear fashion. In humans, activity in a similar set of brain regions has been associated with visuotactile stimulation of the hand. However, little is known about how these areas integrate visual and tactile information. In this functional magnetic resonance imaging experiment, we employed tactile, visual, and visuotactile stimulation of the right hand in an ecologically valid setup where participants were looking directly at their upper limb. We identified brain regions that were activated by both visual and tactile stimuli as well as areas exhibiting greater activity in the visuotactile condition than in both unisensory ones. The posterior and inferior parietal, dorsal, and ventral premotor cortices, as well as the cerebellum, all showed evidence of multisensory linear (additive) responses. Nonlinear, superadditive responses were observed in the cortex lining the left anterior intraparietal sulcus, the insula, dorsal premotor cortex, and, subcortically, the putamen. These results identify a set of candidate frontal, parietal and subcortical regions that integrate visual and tactile information for the multisensory perception of one's own hand.
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84. |
- Granseth, Björn, 1973-, et al.
(författare)
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Unitary EPSCs of corticogeniculate fibers in the rat dorsal lateral geniculate nucleus in vitro
- 2003
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 89:6, s. 2952-2960
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Tidskriftsartikel (refereegranskat)abstract
- To investigate unitary corticogeniculate excitatory postsynaptic currents (EPSCs), whole cell patch-clamp recordings were obtained from 20 principal cells in slices of the dorsal lateral geniculate nucleus (dLGN) of DA-HAN rats. EPSCs, evoked by electrical stimulation of corticogeniculate axons, had size distributions with one or more quantal peaks. Gaussian curves fitted to such distributions gave a mean quantal size (q) of -5.0 ± 0.7 (SD) pA for the EPSCs. Paired-pulse ratio (EPSC2/EPSC1) was 3.3 ± 0.9 for stimuli separated by 40 ms. The mean quantal size was similar for facilitated EPSCs (-5.2 ± 0.8 pA), implying an increase in mean quantal content (m). Most corticogeniculate axons were capable of releasing only one or two quanta onto individual principal cells. Mean resting release probability (p) was low, 0.09 ± 0.04. Binomial models, with the same n but increased p, could account for both the basal and facilitated EPSC size distributions in 6/8 cells. It is suggested that the low resting efficacy of corticogeniculate synapses serves to stabilize this excitatory feedback system. The pronounced facilitation in conjunction with large convergence from many corticogeniculate cells would provide a transient, potent excitation of dLGN cells, compliant with the idea of a visually driven neuronal amplifier.
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85. |
- Grillner, S
(författare)
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The execution of movement: a spinal affair
- 2021
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 125:2, s. 693-698
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Tidskriftsartikel (refereegranskat)abstract
- In this tribute to Reggie Edgerton, I briefly review the spinal mechanisms that coordinate locomotion and the interaction between the different sensory mechanisms that help coordinate the locomotor movements and the central locomotor network. The step cycle has four distinct parts, the support phase, the lift off, the flexion phase, and, the most complex, the touch down, when the limb makes a smooth contact with ground again. Each of these phases is affected by different sensory mechanisms, which interact with the central network [central pattern generator (CPG)] generating the basic movements with its four components. Conversely, the CPG also gates the sensory reflex pathways, so that they are active only in a given phase of the step cycle, or even produces opposite effects in different parts of the step cycle. These different examples from mammals are most likely important also to consider for human locomotion and, in particular, in patients with spinal cord injury, partial or complete.
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86. |
- Halje, Pär, et al.
(författare)
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Oscillations in cortico-basal ganglia circuits : implications for Parkinson's disease and other neurologic and psychiatric conditions
- 2019
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Ingår i: Journal of Neurophysiology. - : AMER PHYSIOLOGICAL SOC. - 0022-3077 .- 1522-1598. ; 122:1, s. 203-231
-
Forskningsöversikt (refereegranskat)abstract
- Cortico-basal ganglia circuits are thought to play a crucial role in the selection and control of motor behaviors and have also been implicated in the processing of motivational content and in higher cognitive functions. During the last two decades, electro-physiological recordings in basal ganglia circuits have shown that several disease conditions are associated with specific changes in the temporal patterns of neuronal activity. In particular, synchronized oscillations have been a frequent finding suggesting that excessive synchronization of neuronal activity may be a pathophysiological mechanism involved in a wide range of neurologic and psychiatric conditions. We here review the experimental support for this hypothesis primarily in relation to Parkinson's disease but also in relation to dystonia, essential tremor, epilepsy, and psychosis/schizophrenia.
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87. |
- Hao, JX, et al.
(författare)
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Response characteristics of spinal cord dorsal horn neurons in chronic allodynic rats after spinal cord injury
- 2004
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 92:3, s. 1391-1399
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Tidskriftsartikel (refereegranskat)abstract
- The physiological mechanisms of chronic pain in patients with spinal cord injury (SCI) are poorly understood. In the present study, we explored response characteristics of dorsal horn neurons of spinally injured rats exhibiting chronic pain (pain-like response to innocuous mechanical and cold stimulation). Several abnormalities were found in the distribution and response characteristics of dorsal horn neurons in chronic allodynic rats. First, 17% of the recorded neurons (vs. 0% in control animals) had no receptive field. Most of these units were located at or close to the lesioned spinal segment, and they discharged spontaneously at high frequencies. Allodynic rats also showed a significant decrease in the proportion of low-threshold (LT) neurons and an increase in the proportion of wide dynamic range (WDR) neurons. The rate of spontaneous activity of high-threshold (HT) neurons was significantly higher in allodynic compared with control rats. Moreover, HT neurons in allodynic animals showed increased neuronal responses to mechanical stimulation. WDR neurons responded with higher discharge rates to innocuous von Frey hair stimulation in allodynic compared with control rats. The percentage of WDR and HT neurons showing afterdischarges to noxious pinch was also significantly increased in the allodynic rats. The proportion of WDR and HT neurons responding to innocuous cold stimulation respectively increased from 53 and 25% in control rats to 91 and 75% in allodynic animals. These results suggest that the chronic pain-like behaviors in spinally injured rats may be generated and maintained by abnormalities in dorsal horn neurons.
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88. |
- Hellgren Kotaleski, Jeanette, et al.
(författare)
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Using potassium currents to solve signal-to-noise problems in inhibitory feedforward networks of the striatum
- 2006
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 95:1, s. 331-341
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Tidskriftsartikel (refereegranskat)abstract
- Using potassium currents to solve signal-to-noise problems in inhibitory feedforward networks of the striatum. J Neurophysiol 95: 331 - 341, 2006. First published September 28, 2005; doi: 10.1152/jn. 00063.2005. Fast-spiking (FS) interneurons provide the main route of feedforward inhibition from cortex to spiny projection neurons in the striatum. A steep current-firing frequency curve and a dense local axonal arbor suggest that even small excitatory inputs could translate into powerful feedforward inhibition, although such an arrangement is also sensitive to amplification of spurious synaptic inputs. We show that a transient potassium (KA) current allows the FS interneuron to strike a balance between sensitivity to correlated input and robustness to noise, thereby increasing its signal-to-noise ratio (SNR). First, a compartmental FS neuron model was created to match experimental data from striatal FS interneurons in cortex - striatum - substantia nigra organotypic cultures. Densities of sodium, delayed rectifier, and KA channels were optimized to replicate responses to somatic current injection. Spontaneous alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and gamma-aminobutyric acid ( GABA) synaptic currents were adjusted to the experimentally measured amplitude, rise time, and interevent interval histograms. Second, two additional adjustments were required to emulate the remaining experimental observations. GABA channels were localized closer to the soma than AMPA channels to match the synaptic population reversal potential. Correlation among inputs was required to produce the observed firing rate during up-states. In this final model, KA channels were essential for suppressing down-state spikes while allowing reliable spike generation during up-states. This mechanism was particularly important under conditions of high dopamine. Our results suggest that KA channels allow FS interneurons to operate without a decrease in SNR during conditions of increased dopamine, as occurs in response to reward or anticipated reward.
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89. |
- Hess, D, et al.
(författare)
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Characterization of Na+-activated K+ currents in larval lamprey spinal cord neurons
- 2007
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 97:5, s. 3484-3493
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Tidskriftsartikel (refereegranskat)abstract
- Potassium channels play an important role in controlling neuronal firing and synaptic interactions. Na+-activated K+ ( KNa) channels have been shown to exist in neurons in different regions of the CNS, but their physiological function has been difficult to assess. In this study, we have examined if neurons in the spinal cord possess KNa currents. We used whole cell recordings from isolated spinal cord neurons in lamprey. These neurons display two different KNa currents. The first was transient and activated by the Na+ influx during the action potentials, and it was abolished when Na+ channels were blocked by tetrodotoxin. The second KNa current was sustained and persisted in tetrodotoxin. Both KNa currents were abolished when Na+ was substituted with choline or N-methyl-d-glucamine, indicating that they are indeed dependent on Na+ influx into neurons. When Na+ was substituted with Li+, the amplitude of the inward current was unchanged, whereas the transient KNa current was reduced but not abolished. This suggests that the transient KNa current is partially activated by Li+. These two KNa currents have different roles in controlling the action potential waveform. The transient KNa appears to act as a negative feedback mechanism sensing the Na+ influx underlying the action potential and may thus be critical for setting the amplitude and duration of the action potential. The sustained KNa current has a slow kinetic of activation and may underlie the slow Ca2+-independent afterhyperpolarization mediated by repetitive firing in lamprey spinal cord neurons.
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90. |
- Hirschfeld, H, et al.
(författare)
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Coordinated ground forces exerted by buttocks and feet are adequately programmed for weight transfer during sit-to-stand
- 1999
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 82:6, s. 3021-3029
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to test the hypothesis whether weight transfer during sit-to-stand (STS) is the result of coordinated ground forces exerted by buttocks and feet before seat-off. Whole-body kinematics and three-dimensional ground forces from left and right buttock as well as from left and right foot were recorded for seven adults during STS. We defined a preparatory phase from onset of the first detectable anterior/posterior (A/P) force to seat-off (buttock forces fell to 0) and a rising phase from seat-off to the decrease of center of mass (CoM) vertical velocity to zero. STS was induced by an increase of vertical and backward directed ground forces exerted by the buttocks that significantly preceded the onset of any trunk movement. All ground forces peaked before or around the moment of seat-off, whereas all kinematic variables, except trunk forward rotation and hip flexion, peaked after seat-off, during or after the rising phase. The present study suggests that the weight transfer from sit to stand is induced by ground forces exerted by buttocks and feet before seat-off, i.e., during the preparatory phase. The buttocks generate the isometric “rising forces,” e.g., the propulsive impulse for the forward acceleration of the body, while the feet apply adequate damping control before seat-off. This indicates that the rising movement is a result of these coordinated forces, targeted to match the subject's weight and support base distance between buttocks and feet. The single peaked, bell-shaped profiles peaking before seat-off, were seen beneath buttocks for the “rising drive,” i.e., between the time of peak backward directed force and seat-off, as well as beneath the feet for the “damping drive,” i.e., from onset to the peak of forward-directed force and for CoM A/P velocity. This suggests that both beginning and end of the weight transfer process are programmed before seat-off. The peak deceleration of A/P CoM took place shortly (∼100 ms) after CoM peak velocity, resulting in a well controlled CoM deceleration before seat-off. In contrast to the view of other authors, this suggests that body equilibrium is controlled during weight transfer.
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91. |
- Hsu, LJ, et al.
(författare)
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Effects of galvanic vestibular stimulation on postural limb reflexes and neurons of spinal postural network
- 2012
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 108:1, s. 300-313
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Tidskriftsartikel (refereegranskat)abstract
- Quadrupeds maintain the dorsal side up body orientation due to the activity of the postural control system driven by limb mechanoreceptors. Binaural galvanic vestibular stimulation (GVS) causes a lateral body sway toward the anode. Previously, we have shown that this new position is actively stabilized, suggesting that GVS changes a set point in the reflex mechanisms controlling body posture. The aim of the present study was to reveal the underlying neuronal mechanisms. Experiments were performed on decerebrate rabbits. The vertebral column was rigidly fixed, whereas hindlimbs were positioned on a platform. Periodic lateral tilts of the platform caused postural limb reflexes (PLRs): activation of extensors in the loaded and flexing limb and a decrease in extensor activity in the opposite (unloaded and extending) limb. Putative spinal interneurons were recorded in segments L4–L5 during PLRs, with and without GVS. We have found that GVS enhanced PLRs on the cathode side and reduced them on the anode side. This asymmetry in PLRs can account for changes in the stabilized body orientation observed in normal rabbits subjected to continuous GVS. Responses to platform tilts (frequency modulation) were observed in 106 spinal neurons, suggesting that they can contribute to PLR generation. Two neuron groups were active in opposite phases of the tilt cycle of the ipsi-limb: F-neurons in the flexion phase, and E-neurons in the extension phase. Neurons were driven mainly by afferent input from the ipsi-limb. If one supposes that F- and E-neurons contribute, respectively, to excitation and inhibition of extensor motoneurons, one can expect that the pattern of response to GVS in F-neurons will be similar to that in extensor muscles, whereas E-neurons will have an opposite pattern. We have found that ∼40% of all modulated neurons meet this condition, suggesting that they contribute to the generation of PLRs and to the GVS-caused changes in PLRs.
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92. |
- Hu, GY, et al.
(författare)
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Intracellular QX-314 causes depression of membrane potential oscillations in lamprey spinal neurons during fictive locomotion
- 2002
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 87:6, s. 2676-2683
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Tidskriftsartikel (refereegranskat)abstract
- Spinal neurons undergo large cyclic membrane potential oscillations during fictive locomotion in lamprey. It was investigated whether these oscillations were due only to synaptically driven excitatory and inhibitory potentials or if voltage-dependent inward conductances also contribute to the depolarizing phase by using N-(2,6-dimethylphenyl carbamoylmethyl)triethylammonium bromide (QX-314) administered intracellularly during fictive locomotion. QX-314 intracellularly blocks inactivating and persistent Na+ channels, and in some neurons, effects on certain other types of channels have been reported. To detail the effects of QX-314 on Na+ and Ca2+ channels, we used dissociated lamprey neurons recorded under whole cell voltage clamp. At low intracellular concentrations of QX-314 (0.2 mM), inactivating Na+ channels were blocked and no effects were exerted on Ca2+ channels (also at 0.5 mM). At 10 mM QX-314, there was, however a marked reduction of I Ca. In the isolated spinal cord of the lamprey, fictive locomotion was induced by superfusing the spinal cord with Ringer's solution containing N-methyl-d-aspartate (NMDA), while recording the locomotor activity from the ventral roots. Simultaneously, identified spinal neurons were recorded intracellularly, while infusing QX-314 from the microelectrode. Patch electrodes cannot be used in the intact spinal cord, and therefore “sharp” electrodes were used. The amplitude of the oscillations was consistently reduced by 20–25% in motoneurons ( P < 0.05) and unidentified spinal neurons ( P < 0.005). The onset of the effect started a few minutes after impalement and reached a stable level within 30 min. These effects thus show that QX-314 causes a reduction in the amplitude of membrane potential oscillations during fictive locomotion. We also investigated whether QX-314 could affect glutamate currents by applying short pulses of glutamate from an extracellular pipette. No changes were observed. We also found no evidence for a persistent Na+ current in dissociated neurons, but these cells have a much-reduced dendritic tree. The results indicate that there is an inward conductance, which is sensitive to QX-314, during membrane potential oscillations that “boosts” the synaptic drive during fictive locomotion. Taken together, the results suggest that inactivating Na+ channels contribute to this inward conductance although persistent Na+channels, if present on dendrites, could possibly also contribute to shaping the membrane potential oscillations.
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93. |
- Hudson, K. M., et al.
(författare)
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Effects of changing skin mechanics on the differential sensitivity to surface compliance by tactile afferents in the human finger pad
- 2015
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 114:4, s. 2249-2257
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Tidskriftsartikel (refereegranskat)abstract
- It is not known how changes in skin mechanics affect the responses of cutaneous mechanoreceptors in the finger pads to compression forces. We used venous occlusion to change the stiffness of the fingers and investigated whether this influenced the firing of low-threshold mechanoreceptors to surfaces of differing stiffness. Unitary recordings were made from 10 slowly adapting type I (SAI), 10 fast adapting type I (FAI) and 9 slowly adapting type II (SAII) units via tungsten microelectrodes inserted into the median nerve at the wrist. A servocontrolled stimulator applied ramp-and-hold forces (1, 2, and 4 N) at a constant loading and unloading rate (2 N/s) via a flat 2.5-cmdiameter silicone disk over the center of the finger pad. Nine silicone disks (objects), varying in compliance, were used. Venous occlusion, produced by inflating a sphygmomanometer cuff around the upper arm to 40±5 mmHg, was used to induce swelling of the fingers and increase the compliance of the finger pulp. Venous occlusion had no effect on the firing rates of the SAI afferents, nor on the slopes of the relationship between mean firing rate and object compliance at each amplitude, but did significantly reduce the slopes for the FAI afferents. Although the SAII afferents possess a poor capacity to encode changes in object compliance, mean firing rates were significantly lower during venous occlusion. The finding that venous occlusion had no effect on the firing properties of SAI afferents indicates that these afferents preserve their capacity to encode changes in object compliance, despite changes in skin mechanics. © 2015 the American Physiological Society.
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94. |
- Huss, Mikael, et al.
(författare)
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Roles of ionic currents in lamprey CPG neurons : a modeling study
- 2007
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 97:4, s. 2696-2711
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Tidskriftsartikel (refereegranskat)abstract
- The spinal network underlying locomotion in the lamprey consists of a core network of glutamatergic and glycinergic interneurons, previously studied experimentally and through mathematical modeling. We present a new and more detailed computational model of lamprey locomotor network neurons, based primarily on detailed electrophysiological measurements and incorporating new experimental findings. The model uses a Hodgkin Huxley-like formalism and consists of 86 membrane compartments containing 12 types of ion currents. One of the goals was to introduce a fast, transient potassium current (K-t) and two sodium-dependent potassium currents, one faster (K-NaF) and one slower (K-NaS), in the model. Not only has the model lent support to the interpretation of experimental results but it has also provided predictions for further experimental analysis of single-network neurons. For example, K-t was shown to be one critical factor for controlling action potential duration. In addition, the model has proved helpful in investigating the possible influence of the slow afterhyperpolarization on repetitive firing during ongoing activation. In particular, the balance between the simulated slow sodium-dependent and calcium-dependent potassium currents has been explored, as well as the possible involvement of dendritic conductances.
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95. |
- Igelström, Kajsa, 1980-, et al.
(författare)
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Low-magnesium medium induces epileptiform activity in mouse olfactory bulb slices
- 2011
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Ingår i: Journal of Neurophysiology. - Rockville, MD, United States : American Physiological Society. - 0022-3077 .- 1522-1598. ; 106:5, s. 2593-2605
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Tidskriftsartikel (refereegranskat)abstract
- Magnesium-free medium can be used in brain slice studies to enhance glutamate receptor function, but this manipulation causes seizure-like activity in many cortical areas. The rodent olfactory bulb (OB) slice is a popular preparation, and potentially ictogenic ionic conditions have often been used to study odor processing. We studied low Mg2+-induced epileptiform discharges in mouse OB slices using extracellular and whole cell electrophysiological recordings. Low-Mg2+ medium induced two distinct types of epileptiform activity: an intraglomerular delta-frequency oscillation resembling slow sniff-induced activity and minute-long seizure-like events (SLEs) consisting of large negative-going field potentials accompanied by sustained depolarization of output neurons. SLEs were dependent on N-methyl-d-aspartate receptors and sodium currents and were facilitated by α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors. The events were initiated in the glomerular layer and propagated laterally through the external plexiform layer at a slow time scale. Our findings confirm that low-Mg2+ medium should be used with caution in OB slices. Furthermore, the SLEs resembled the so-called slow direct current (DC) shift of clinical and experimental seizures, which has recently been recognized as being of great clinical importance. The OB slice may therefore provide a robust and unique in vitro model of acute seizures in which mechanisms of epileptiform DC shifts can be studied in isolation from fast oscillations.
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96. |
- Isa, Tadashi, et al.
(författare)
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Properties of propriospinal neurons in the C3-C4 segments mediating disynaptic pyramidal excitation to forelimb motoneurons in the macaque monkey.
- 2006
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 95:6, s. 3674-85
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Tidskriftsartikel (refereegranskat)abstract
- Candidate propriospinal neurons (PNs) that mediate disynaptic pyramidal excitation to forelimb motoneurons were studied in the C3-C4 segments in anesthetized macaque monkeys (n = 10). A total of 177 neurons were recorded (145 extracellularly, 48 intracellularly, and 16 both) in laminae VI-VII. Among these, 86 neurons (73 extracellularly, 14 intracellularly and 1 both) were antidromically activated from the forelimb motor nucleus or from the ventrolateral funiculus just lateral to the motor nucleus in the C6/C7 segments and thus are identified as PNs. Among the 73 extracellularly recorded PNs, 60 cells were fired by a train of four stimuli to the contralateral pyramid with segmental latencies of 0.8-2.2 ms, with most of them (n = 52) in a monosynaptic range (<1.4 ms including one synaptic delay and time to firing). The firing probability was only 21% from the third pyramidal volley but increased to 83% after intravenous injection of strychnine. In most of the intracellularly recorded PNs, stimulation of the contralateral pyramid evoked monosynaptic excitatory postsynaptic potentials (EPSPs, 12/14) and disynaptic inhibitory postsynaptic potentials (14/14), which were found to be glycinergic. In contrast, cells that did not project to the C6-Th1 segments where forelimb motoneurons are located were classified as segmental interneurons. These were fired from the third pyramidal volley with a probability of 71% before injection of strychnine. It is proposed that some of these interneurons mediate feed-forward inhibition to the PNs. These results suggest that the C3-C4 PNs receive feed-forward inhibition from the pyramid in addition to monosynaptic excitation and that this inhibition is stronger in the macaque monkey than in the cat. Another difference with the cat was that only 26 of the 86 PNs (30%, as compared with 84% in the cat) with projection to the forelimb motor nuclei send ascending collaterals terminating in the lateral reticular nucleus (LRN) on the ipsilateral side of the medulla. Thus we identified C3-C4 PNs that could mediate disynaptic pyramidal excitation to forelimb motoneurons in the macaque monkey. The present findings explain why it was difficult in previous studies of the macaque monkey to evoke disynaptic pyramidal excitation via C3-C4 PNs in forelimb motoneurons and why-as compared with the cat-the monosynaptic EPSPs evoked from the LRN via C3-C4 PNs were smaller in amplitude.
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97. |
- Islam, SS, et al.
(författare)
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Modifications of locomotor pattern underlying escape behavior in the lamprey
- 2008
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 99:1, s. 297-307
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Tidskriftsartikel (refereegranskat)abstract
- Two forms of undulatory locomotion in the lamprey (a lower vertebrate) have been described earlier: fast forward swimming (FFS) used for long distance migrations and slow backward swimming (SBS) used for escape from adverse tactile stimuli. In the present study, we describe another form of escape behavior: slow forward swimming (SFS). We characterize the kinematic and electromyographic patterns of SFS and compare them with SBS and FFS. The most striking feature of SFS is nonuniformity of shape and speed of the locomotor waves propagating along the body: close to the site of stimulation, the waves slow down and the body curvature increases several-fold due to enhanced muscle activity. Lesions of afferents showed that sensory information critical for elicitation of SFS is transmitted through the dorsal roots. In contrast, sensory signals that induce SBS are transmitted through the dorsal roots, lateral line nerves, and trigeminal nerves. Persistence of SFS and SBS after different lesions of the spinal cord suggests that the ascending and descending pathways, necessary for induction of SBS and SFS, are dispersed over the cross section of the spinal cord. As shown previously, during FFS (but not SBS) the lamprey maintains the dorsal-side-up body orientation due to vestibular postural reflexes. In this study we have found that the orientation control is absent during SFS. The role of the spinal cord and the brain stem in generation of different forms of undulatory locomotion is discussed.
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98. |
- Islam, SS, et al.
(författare)
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Pattern of motor coordination underlying backward swimming in the lamprey
- 2006
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 96:1, s. 451-460
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Tidskriftsartikel (refereegranskat)abstract
- The main form of locomotion in the lamprey (a lower vertebrate, cyclostome) is forward swimming (FS) based on periodical waves of lateral body flexion propagating from head to tail. The lamprey is also capable of backward swimming (BS). Here we describe the kinematical and electromyographic (EMG) pattern of BS, as well as the effects on this pattern exerted by different lesions of the spinal cord. The BS was evoked by tactile stimulation of a large area in the anterior part of the body. Swimming was attributed to the waves of lateral body undulations propagating from tail to head. The EMG bursts on the two sides alternated, and the EMG in more caudal segments led in phase the EMG in more rostral segments. Main kinematical characteristics of BS strongly differed from those of FS: the amplitude of undulations was much larger and their frequency lower. Also, the maintenance of the dorsal-side-up body orientation ascribed to vestibular postural reflexes (typical for FS) was not observed during BS. A complete transection of the spinal cord did not abolish the generation of forward-propagating waves rostral to the lesion. After a lateral hemisection of the spinal cord, the BS pattern persisted on both sides rostral to the lesion; caudal to the lesion, it was present on the intact side and reduced or abolished on the lesioned side. The role of the spinal cord in generation of different forms of undulatory locomotion (FS and BS) is discussed.
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99. |
- Israeli-Korn, SD, et al.
(författare)
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Intersegmental coordination patterns are differently affected in Parkinson's disease and cerebellar ataxia
- 2019
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 121:2, s. 672-689
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Tidskriftsartikel (refereegranskat)abstract
- The law of intersegmental coordination (Borghese et al. 1996) may be altered in pathological conditions. Here we investigated the contribution of the basal ganglia (BG) and the cerebellum to lower limb intersegmental coordination by inspecting the plane’s orientation and other parameters pertinent to this law in patients with idiopathic Parkinson’s disease (PD) or cerebellar ataxia (CA). We also applied a mathematical model that successfully accounts for the intersegmental law of coordination observed in control subjects (Barliya et al. 2009). In the present study, we compared the planarity index (PI), covariation plane (CVP) orientation, and CVP orientation predicted by the model in 11 PD patients, 8 CA patients, and two groups of healthy subjects matched for age, height, weight, and gender to each patient group (Ctrl_PD and Ctrl_CA). Controls were instructed to alter their gait speed to match those of their respective patient group. PD patients were examined after overnight withdrawal of anti-parkinsonian medications (PD-off-med) and then on medication (PD-on-med). PI was above 96% in all gait conditions in all groups suggesting that the law of intersegmental coordination is preserved in both BG and cerebellar pathology. However, the measured and predicted CVP orientations rotated in PD-on-med and PD-off-med compared with Ctrl_PD and in CA vs. Ctrl_CA. These rotations caused by PD and CA were in opposite directions suggesting differences in the roles of the BG and cerebellum in intersegmental coordination during human locomotion. NEW & NOTEWORTHY Kinematic and muscular synergies may have a role in overcoming motor redundancies, which may be reflected in intersegmental covariation. Basal ganglia and cerebellar networks were suggested to be involved in crafting and modulating synergies. We thus compared intersegmental coordination in Parkinson’s disease and cerebellar disease patients and found opposite effects in some aspects. Further research integrating muscle activities as well as biomechanical and neural control modeling are needed to account for these findings.
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100. |
- Ivarsson, Magnus, et al.
(författare)
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Conditioned eyeblink response consists of two distinct components
- 2000
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 83:2, s. 796-807
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Tidskriftsartikel (refereegranskat)abstract
- The aim of these experiments was to obtain a detailed knowledge of how the orbicularis oculi muscle is activated during the execution of a conditioned eyeblink response (CR). This is the first critical step to understand the underlying neural mechanisms involved in the control of the CR. Decerebrate ferrets were trained in a classical conditioning paradigm. The conditioned stimulus (CS) was a train of electrical stimuli (15 pulses, 50 Hz, 1 mA) applied to the forelimb, and the unconditioned stimulus (US) was a train of electrical stimuli (3 pulses, 50 Hz, 3-4 mA) to the periorbital region. The CRs were studied by recording electromyograms (EMGs) from the orbicularis oculi muscle. The eyeblink CR in all animals showed a similar topography with at least two different components, CR1 and CR2, which were expressed at different rates. CR1 appeared first during acquisition, had a shorter onset latency, and was more phasic and more resistant to extinction than CR2. A marked pause in the muscle activity separated the two components. To control that the two-component CR were not species, paradigm or preparation specific, awake rabbits were trained with a tone CS (300 ms, 4 kHz, 64 dB) and a train of periorbital stimuli as US (3 pulses, 50 Hz, 3 mA). CR1 and CR2 were present in the rabbit eyeblink CR. The cerebellum is implicated in the control of CRs and to study whether separate neural pathways were responsible for CR1 and CR2, direct brachium pontis stimulation was used to replace the forelimb CS. CR1 and CR2 were present in the CR elicited by the brachium pontis CS. The presence of CR1 and CR2 after a unilateral lesion of the brachium conjunctivum shows that output from the contralateral cerebellar hemisphere was not the cause for any of the components. Other mechanisms that might be involved in the separation of the CR into two components are discussed. The results show that the eyeblink CR consists of at least two components, CR1 and CR2, which most likely originate either as a direct central command from the cerebellum or in the output pathway before the facial nucleus.
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