| 1. |
- Bengtsson, Fredrik, et al.
(författare)
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In Vivo Analysis of Inhibitory Synaptic Inputs and Rebounds in Deep Cerebellar Nuclear Neurons
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Neuronal function depends on the properties of the synaptic inputs the neuron receive and on its intrinsic responsive properties. However, the conditions for synaptic integration and activation of intrinsic responses may to a large extent depend on the level of background synaptic input. In this respect, the deep cerebellar nuclear (DCN) neurons are of particular interest: they feature a massive background synaptic input and an intrinsic, postinhibitory rebound depolarization with profound effects on the synaptic integration. Using in vivo whole cell patch clamp recordings from DCN cells in the cat, we find that the background of Purkinje cell input provides a tonic inhibitory synaptic noise in the DCN cell. Under these conditions, individual Purkinje cells appear to have a near negligible influence on the DCN cell and clear-cut rebounds are difficult to induce. Peripheral input that drives the simple spike output of the afferent PCs to the DCN cell generates a relatively strong DCN cell inhibition, but do not induce rebounds. In contrast, synchronized climbing fiber activation, which leads to a synchronized input from a large number of Purkinje cells, can induce profound rebound responses. In light of what is known about climbing fiber activation under behaviour, the present findings suggest that DCN cell rebound responses may be an unusual event. Our results also suggest that cortical modulation of DCN cell output require a substantial co-modulation of a large proportion of the PCs that innervate the cell, which is a possible rationale for the existence of the cerebellar microcomplex.
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| 2. |
- Van Dijck, Gert, et al.
(författare)
-
Probabilistic Identification of Cerebellar Cortical Neurones across Species
- 2013
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:3
-
Tidskriftsartikel (refereegranskat)abstract
- Despite our fine-grain anatomical knowledge of the cerebellar cortex, electrophysiological studies of circuit information processing over the last fifty years have been hampered by the difficulty of reliably assigning signals to identified cell types. We approached this problem by assessing the spontaneous activity signatures of identified cerebellar cortical neurones. A range of statistics describing firing frequency and irregularity were then used, individually and in combination, to build Gaussian Process Classifiers (GPC) leading to a probabilistic classification of each neurone type and the computation of equiprobable decision boundaries between cell classes. Firing frequency statistics were useful for separating Purkinje cells from granular layer units, whilst firing irregularity measures proved most useful for distinguishing cells within granular layer cell classes. Considered as single statistics, we achieved classification accuracies of 72.5% and 92.7% for granular layer and molecular layer units respectively. Combining statistics to form twin-variate GPC models substantially improved classification accuracies with the combination of mean spike frequency and log-interval entropy offering classification accuracies of 92.7% and 99.2% for our molecular and granular layer models, respectively. A cross-species comparison was performed, using data drawn from anaesthetised mice and decerebrate cats, where our models offered 80% and 100% classification accuracy. We then used our models to assess non-identified data from awake monkeys and rabbits in order to highlight subsets of neurones with the greatest degree of similarity to identified cell classes. In this way, our GPC-based approach for tentatively identifying neurones from their spontaneous activity signatures, in the absence of an established ground-truth, nonetheless affords the experimenter a statistically robust means of grouping cells with properties matching known cell classes. Our approach therefore may have broad application to a variety of future cerebellar cortical investigations, particularly in awake animals where opportunities for definitive cell identification are limited.
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| 3. |
- Alstermark, Bror, et al.
(författare)
-
The lateral reticular nucleus : integration of descending and ascending systems regulating voluntary forelimb movements
- 2015
-
Ingår i: Frontiers in Computational Neuroscience. - : Frontiers Media SA. - 1662-5188. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Cerebellar control of movements is dependent on mossy fiber input conveying information about sensory and premotor activity in the spinal cord. While much is known about spino-cerebellar systems, which provide the cerebellum with detailed sensory information, much less is known about systems conveying motor information. Individual motoneurones do not have projections to spino-cerebellar neurons. Instead, the fastest route is from last order spinal interneurons. In order to identify the networks that convey ascending premotor information from last order interneurons, we have focused on the lateral reticular nucleus (LRN), which provides the major mossy fiber input to cerebellum from spinal interneuronal systems. Three spinal ascending systems to the LRN have been investigated: the C3-C4 propriospinal neurones (PNs), the ipsilateral forelimb tract (iFT) and the bilateral ventral flexor reflex tract (bVFRT). Voluntary forelimb movements involve reaching and grasping together with necessary postural adjustments and each of these three interneuronal systems likely contribute to specific aspects of forelimb motor control. It has been demonstrated that the command for reaching can be mediated via C3-C4 PNs, while the command for grasping is conveyed via segmental interneurons in the forelimb segments. Our results reveal convergence of ascending projections from all three interneuronal systems in the LRN, producing distinct combinations of excitation and inhibition. We have also identified a separate descending control of LRN neurons exerted via a subgroup of cortico-reticular neurones. The LRN projections to the deep cerebellar nuclei exert a direct excitatory effect on descending motor pathways via the reticulospinal, vestibulospinal, and other supraspinal tracts, and might play a key role in cerebellar motor control. Our results support the hypothesis that the LRN provides the cerebellum with highly integrated information, enabling cerebellar control of complex forelimb movements.
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| 4. |
- Alstermark, Bror, et al.
(författare)
-
The lateral reticular nucleus : a precerebellar centre providing the cerebellum with overview and integration of motor functions at systems level. A new hypothesis.
- 2013
-
Ingår i: Journal of Physiology. - : Wiley-Blackwell. - 0022-3751 .- 1469-7793. ; 591:22, s. 5453-5458
-
Tidskriftsartikel (refereegranskat)abstract
- The lateral reticular nucleus (LRN) is a major precerebellar centre of mossy fibre information to the cerebellum from the spinal cord that is distinct from the direct spinocerebellar paths. The LRN has traditionally been considered to provide the cerebellum with segregated information from several spinal systems controlling posture, reaching, grasping, locomotion, scratching and respiration. However, results are presented that show extensive convergence on a majority of LRN neurons from spinal systems. We propose a new hypothesis suggesting that the LRN may use extensive convergence from the different input systems to provide overview and integration of linked motor components to the cerebellum. This integrated information is sent in parallel with the segregated information from the individual systems to the cerebellum that finally may compare the activity and make necessary adjustments of various motor behaviours.
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| 5. |
- Dean, Paul, et al.
(författare)
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The cerebellar microcircuit as an adaptive filter: experimental and computational evidence
- 2010
-
Ingår i: Nature Reviews Neuroscience. - : Springer Science and Business Media LLC. - 1471-003X .- 1471-0048. ; 11:1, s. 30-43
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Forskningsöversikt (refereegranskat)abstract
- Initial investigations of the cerebellar microcircuit inspired the Marr-Albus theoretical framework of cerebellar function. We review recent developments in the experimental understanding of cerebellar microcircuit characteristics and in the computational analysis of Marr-Albus models. We conclude that many Marr-Albus models are in effect adaptive filters, and that evidence for symmetrical long-term potentiation and long-term depression, interneuron plasticity, silent parallel fibre synapses and recurrent mossy fibre connectivity is strikingly congruent with predictions from adaptive-filter models of cerebellar function. This congruence suggests that insights from adaptive-filter theory might help to address outstanding issues of cerebellar function, including both microcircuit processing and extra-cerebellar connectivity.
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| 6. |
- Ekerot, Carl-Fredrik, et al.
(författare)
-
Chapter 24 The control of forelimb movements by intermediate cerebellum
- 1997
-
Ingår i: Progress in brain research. - 0079-6123. - 0444801049 ; 114, s. 423-429
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In a series of studies, the functional organization of cerebellar regions contributing to the control of forelimb movements via the rubro- and corticospinal tracts has been characterized in the cat. The system consists of the cerebellar cortical C1, C3 and Y zones and their efferent intracerebellar nucleus, the interpositus anterior. Based on analyses of cutaneous and muscle afferent climbing fibre input, of corticonuclear connections and of limb movements controlled, a modular organization of this cerebellar control system is proposed. Each module consists of a number of cortical microzones, defined by their homogeneous climbing fibre input, and a group of neurones in nucleus interpositus anterior on which these microzones converge. The input to climbing fibres is multi-modal and originates from cutaneous A beta (tactile), A delta and C (nociceptive) fibres and from muscle afferents. The cutaneous receptive fields have spatial characteristics suggestive of a relation to elemental movements. For most climbing fibres, the spatial relationship between cutaneous and muscle afferent input is such that the muscle afferent input originates from muscles that, if activated, would tend to move the cutaneous receptive field of the climbing fibre towards a stimulus applied to the skin. By contrast, the limb movement controlled by the module often has the opposite direction, and would thus tend to move the cutaneous receptive field away from a stimulus applied to the skin. Functional implications of this organization for the involvement of these regions in acute and adaptive motor control of limb movements are discussed.
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| 7. |
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| 8. |
- Ekerot, Carl-Fredrik, et al.
(författare)
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Functional relation between corticonuclear input and movements evoked on microstimulation in cerebellar nucleus interpositus anterior in the cat
- 1995
-
Ingår i: Experimental Brain Research. - 0014-4819. ; 106:3, s. 365-376
-
Tidskriftsartikel (refereegranskat)abstract
- The functional relation between receptive fields of climbing fibres projecting to the C1, C3 and Y zones and forelimb movements controlled by nucleus interpositus anterior via the rubrospinal tract were studied in cats decerebrated at the pre-collicular level. Microelectrode tracks were made through the caudal half of nucleus interpositus anterior. This part of the nucleus receives its cerebellar cortical projection from the forelimb areas of these three sagittal zones. The C3 zone has been demonstrated to consist of smaller functional units called microzones. Natural stimulation of the forelimb skin evoked positive field potentials in the nucleus. These potentials have previously been shown to be generated by climbing fibre-activated Purkinje cells and were mapped at each nuclear site, to establish the climbing fibre receptive fields of the afferent microzones. The forelimb movement evoked by microstimulation at the same site was then studied. The movement usually involved more than one limb segment. Shoulder retraction and elbow flexion were frequently evoked, whereas elbow extension was rare and shoulder protraction never observed. In total, movements at the shoulder and/or elbow occurred for 96% of the interpositus sites. At the wrist, flexion and extension movements caused by muscles with radial, central or ulnar insertions on the paw were all relatively common. Pure supination and pronation movements were also observed. Movements of the digits consisted mainly of dorsal flexion of central or ulnar digits. A comparison of climbing fibre receptive fields and associated movements for a total of 110 nuclear sites indicated a general specificity of the input-output relationship of this cerebellar control system. Several findings suggested that the movement evoked from a particular site would act to withdraw the area of the skin corresponding to the climbing fibre receptive field of the afferent microzones. For example, sites with receptive fields on the dorsum of the paw were frequently associated with palmar flexion at the wrist, whereas sites with receptive fields on the ventral side of the paw and forearm were associated with dorsiflexion at the wrist. Correspondingly, receptive fields on the lateral side of the forearm and paw were often associated with flexion at the elbow, whereas sites with receptive fields on the radial side of the forearm were associated with elbow extension. The proximal movements that were frequently observed also for distal receptive fields may serve to produce a general shortening of the limb to enhance efficiency of the withdrawal. It has previously been suggested that the cerebellar control of forelimb movements via the rubrospinal tract has a modular organisation. Each module would consist of a cell group in the nucleus interpositus anterior and its afferent microzones in the C1, C3 and Y zones, characterised by a homogenous set of climbing fibre receptive fields. The results of the present study support this organisational principle, and suggest that the efferent action of a module is to withdraw the receptive field from an external stimulus. Possible functional interpretations of the action of this system during explorative and reaching movements are discussed.
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| 9. |
- Ekerot, Carl-Fredrik, et al.
(författare)
-
Parallel fiber receptive fields: a key to understanding cerebellar operation and learning.
- 2003
-
Ingår i: Cerebellum. - : Springer Science and Business Media LLC. - 1473-4230. ; 2:2, s. 101-109
-
Tidskriftsartikel (refereegranskat)abstract
- In several theories of the function of the cerebellum in motor control, the mossy-fiber-parallel fiber input has been suggested to provide information used in the control of ongoing movements whereas the role of climbing fibers is to induce plastic changes of parallel fiber (PF) synapses on Purkinje cells. From studies of climbing fibers during the last few decades, we have gained detailed knowledge about the zonal and microzonal organization of the cerebellar cortex and the information carried by climbing fibers. However, properties of the PF input to Purkinje cells and inhibitory interneurones have been largely unknown. The present review, which focuses on the C3 zone of the cerebellar anterior lobe, will present and discuss recent data of the cutaneous PF input to Purkinje cells, interneurons and Golgi cells as well as novel forms of PF plasticity
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| 10. |
- Ekerot, Carl-Fredrik, et al.
(författare)
-
Synaptic Integration in Cerebellar Granule Cells
- 2008
-
Ingår i: Cerebellum. - : Springer Science and Business Media LLC. - 1473-4230. ; 7:4, s. 539-541
-
Tidskriftsartikel (refereegranskat)abstract
- To understand the function of cerebellar granule cells, we need detailed knowledge about the information carried by their afferent mossy fibers and how this information is integrated by the granule cells. Recently, we made whole cell recordings from granule cells in the non-anesthetized, decerebrate cats. All recordings were made in the forelimb area of the C3 zone for which the afferent and efferent connections and functional organization have been investigated in detail. Major findings of the study were that the mossy fiber input to single granule cells was modality- and receptive field-specific and that simultaneous activity in two and usually more of the afferent mossy fibers were required to activate the granule cell spike. The high threshold for action potentials and the convergence of afferents with virtually identical information suggest that an important function of granule cells is to increase the signal-to-noise ratio of the mossy fiber-parallel fiber information. Thus a high-sensitivity, noisy mossy fiber input is transformed by the granule cell to a high-sensitivity, low-noise signal.
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| 11. |
- Ekerot, Carl-Fredrik, et al.
(författare)
-
Topography and nociceptive receptive fields of climbing fibres projecting to the cerebellar anterior lobe in the cat
- 1991
-
Ingår i: Journal of Physiology. - 1469-7793. ; 441:1, s. 257-274
-
Tidskriftsartikel (refereegranskat)abstract
- 1. The cutaneous receptive fields of 225 climbing fibres projecting to the forelimb area of the C3 zone in the cerebellar anterior lobe were mapped in the pentobarbitoneanaesthetized cat. Responses in climbing fibres were recorded as complex spikes in Purkinje cells. 2. A detailed topographical organization of the nociceptive climbing fibre input to the C3 zone was found. In the medial C3 zone climbing fibres with receptive fields covering proximal and/or lateral parts of the forelimb projected most medially. Climbing fibres with receptive fields located more medially on the forelimb projected successively more laterally. The sequence of receptive fields found in the lateral C3 zone was roughly the reverse of that in the medial C3 zone. Climbing fibres with receptive fields restricted to the digits projected preferentially to the caudal part of the forelimb area, whereas those with receptive fields covering both proximal and ventral areas of the forearm projected to more rostral parts. 3. The representation of the forelimb was uneven. Receptive fields with a focus on the digits or along the lateral side of the forearm dominated. 4. The proximal borders of the receptive fields were located close to joints. The area from which maximal responses were evoked was usually located eccentrically within the receptive field. Based on spatial characteristics the receptive fields could be divided into eight classes, which in turn were tentatively divided into subclasses. Similar subclasses of receptive fields were found in different cats. This classification was further supported by the results of a quantitative analysis of eighty-nine climbing fibres. The receptive fields of these climbing fibres were mapped with standardized noxious stimulation. 5. Climbing fibres terminating within sagittal strips (width, 100-300 ,tm; length, > 1 mm) had receptive fields which belonged to the same subclass. There were commonly abrupt changes in receptive fields between such microzones. Most classes of receptive fields were found in both the medial and the lateral parts of the C3 zone. However, receptive fields with a focus on the ventral side of either the metacarpals, the wrist or the forearm were found only in the medial part of the C3 zone. Furthermore, the class of receptive fields restricted to the lateral side of the upper arm and shoulder was only found in the lateral part of the C3 zone. 6. In the discussion, it is proposed that climbing fibres projecting to each microzone carry information from spinal multireceptive reflex arcs acting on a single muscle or a group of synergistic muscles. It is further suggested that each microzone controls the activity of the corresponding motoneurone pool(s) via pathways through the anterior interposed nucleus and the red nucleus.
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| 12. |
- Garwicz, Martin, et al.
(författare)
-
Cutaneous receptive fields and topography of mossy fibres and climbing fibres projecting to cat cerebellar C3 zone
- 1998
-
Ingår i: Journal of Physiology. - 1469-7793. ; 512:1, s. 277-293
-
Tidskriftsartikel (refereegranskat)abstract
- 1. The topographical organization of mossy fibre input to the forelimb area of the paravermal C3 zone in cerebellar lobules IV and V was investigated in barbiturate-anaesthetized cats and compared with the previously described microzonal organization of climbing fibre input to the same part of the cortex. Recordings were made in the Purkinje cell and granule cell layers from single climbing fibre and mossy fibre units, respectively, and the organization of cutaneous receptive fields was assessed for both types of afferents. 2. Based on spatial characteristics, receptive fields of single mossy fibres could be systematized into ten classes and a total of thirty-two subclasses, mainly in accordance with a scheme previously used for classification of climbing fibres. Different mossy fibres displayed a substantial range of sensitivity to natural peripheral stimulation, responded preferentially to phasic or tonic stimuli and were activated by brushing of hairs or light tapping of the skin. 3. Overall, mossy fibres to any given microzone had receptive fields resembling the climbing fibre receptive field defining that microzone. However, compared with the climbing fibre input, the mossy fibre input had a more intricate topographical organization. Mossy fibres with very similar receptive fields projected to circumscribed cortical regions, with a specific termination not only in the mediolateral, but also in some cases in the rostrocaudal and dorsoventral, dimensions of the zone. On the other hand, mossy fibre units with non-identical, albeit usually similar, receptive fields were frequently found in the same microelectrode track.
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| 13. |
- Garwicz, Martin, et al.
(författare)
-
Distribution of Cutaneous Nociceptive and Tactile Climbing Fibre Input to Sagittal Zones in Cat Cerebellar Anterior Lobe
- 1992
-
Ingår i: European Journal of Neuroscience. - : Wiley. - 1460-9568 .- 0953-816X. ; 4:4, s. 289-295
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Tidskriftsartikel (refereegranskat)abstract
- Climbing fibres projecting to the cerebellar C3 zone (and the related C1 and Y zones) receive spatially well organized tactile and nociceptive inputs from the skin. In the present study, cutaneous tactile and nociceptive input to climbing fibres projecting to the X, B, C2 and D1 zones in lobule V were investigated in pentobarbitone-anaesthetized cats. From the present results and previous studies, it is concluded that the X, C1, CX, C3 and Y zones receive cutaneous nociceptive climbing fibre input. By contrast, climbing fibres to the B, C2 and D1 zones lack cutaneous nociceptive input. Tactile input was found in all zones. The spatial organization of receptive fields of climbing fibres projecting to the X and D1 zones was similar to that in the C3 zone. They were located on the ipsilateral forelimb, mainly its lateral and distal parts, and their proximal borders were located close to joints. In the B zone, more than half of the receptive fields of climbing fibres were confined to the ipsilateral hind- or forelimb. However, frequently more than one limb and parts of the trunk were included. In the C2 zone, the majority of climbing fibres had distal ipsi- or bilateral receptive fields on the forelimbs, often also including the head/face. Some of the bilateral forelimb receptive fields additionally included the hindlimbs ipsi- or bilaterally. The results indicate that each zone has a characteristic set of climbing fibre receptive fields, which is probably related to its efferent control functions.
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| 14. |
- Garwicz, Martin, et al.
(författare)
-
Functional organization of the intermediate cerebellum.
- 1995
-
Ingår i: Alpha and Gamma Motor Systems. - Boston, MA : Springer US. - 9780306451867 - 9781461519355 ; , s. 399-402
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Konferensbidrag (refereegranskat)abstract
- The uniform organisation of the neuronal circuitry throughout the cerebellar cortex suggests a uniform mode of operation and thus emphasises the importance of local afferent and efferent connections in determining the function of a particular part of the cortex. Based on the organisation of these connections the cerebellar cortex of the cat is divided into about ten sagittally oriented zones (see Ito, 1984 for references). A zone is anatomically defined by its projection to a restricted part of the intracerebellar or vestibular nuclei and its climbing fibre input from a circumscribed part of the inferior olive. Some of the zones are functionally coupled in that they receive branching collaterals from common olivary neurones and in turn project to the same subdivision of the intracerebellar nuclei. Since each part of the inferior olive receives input from a specific set of spino-olivary pathways, the zones can be electrophysiologically identified by the latencies and receptive fields of climbing fibre responses evoked on peripheral stimulation. The organisation of olivary afferent and nuclear efferent connections suggests that each zone, or in some cases an ensemble of zones, controls specific motor systems.
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| 15. |
- Garwicz, Martin, et al.
(författare)
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Organizational Principles of Cerebellar Neuronal Circuitry
- 1998
-
Ingår i: News in Physiological Sciences. - 1522-161X. ; 13:1, s. 26-32
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Tidskriftsartikel (refereegranskat)abstract
- We review our recent studies of cerebellar neuronal organization, emphasizing that consideration of organizational features of cerebellar circuitry represents a necessary step toward the understanding of how the cerebellum does what it does, in terms of both its internal information processing and its interaction with other motor structures.
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| 16. |
- Garwicz, Martin, et al.
(författare)
-
Topographical organization of the cerebellar cortical projection to nucleus interpositus anterior in the cat
- 1994
-
Ingår i: Journal of Physiology. - 1469-7793. ; 474:2, s. 245-260
-
Tidskriftsartikel (refereegranskat)abstract
- 1. A new methodological approach for detailed study of the organization of the cerebellar corticonuclear projection was evaluated in barbiturate-anaesthetized cats. Extracellular field potentials were simultaneously recorded in nucleus interpositus anterior and in the forelimb area of the C3 zone, at the cerebellar surface. On electrical and natural stimulation of the forelimb skin, the evoked positive field potentials in the nucleus and the climbing fibre field potentials in the cerebellar cortex had similar characteristics, indicating that the nuclear potentials were related to climbing fibre activity. 2. Application of a local anaesthetic to the cerebellar surface reversibly diminished the positive field potentials in the nucleus, demonstrating that the potentials were dependent on cerebellar cortical activity. It was thus concluded that the positive field potentials were mainly generated by climbing fibre-activated Purkinje cells and reflected synaptic inhibitory potentials in nuclear neurones. Accordingly, the positive field potentials in the nucleus could be used to reveal the termination area of Purkinje cells activated by a specific climbing fibre input evoked on peripheral stimulation. 3. The topographical organization of the cerebellar cortical projection to the forelimb part of nucleus interpositus anterior was then investigated by systematically mapping the cutaneous tactile and nociceptive 'receptive fields' of the positive field potentials at different sites in the nucleus. Five groups of receptive fields were distinguished and tentatively divided into a total of nineteen subgroups. 4. Each group of receptive fields corresponded to one or two of the previously described receptive field classes of climbing fibres to the C1, C3 and Y zones and was represented in a single area of the nucleus. Within each area there was an orderly representation of different receptive fields. The results suggest that microzones in the C1, C3 and Y zones with similar climbing fibre input project to a common set of neurones in nucleus interpositus anterior. 5. We propose a modular organization for the cerebellar control of forelimb movements through the rubrospinal tract. Each module would consist of a set of neurones in nucleus interpositus anterior and their afferent microzones in the C1, C3 and Y zones. A module would control a specific group of muscles and receive a homogeneous climbing fibre input related to the movement controlled.
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| 17. |
- Jiang, Juan, et al.
(författare)
-
Direct and indirect spino-cerebellar pathways : shared ideas but different functions in motor control
- 2015
-
Ingår i: Frontiers in Computational Neuroscience. - : Frontiers Media. - 1662-5188. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- The impressive precision of mammalian limb movements relies on internal feedback pathways that convey information about ongoing motor output to cerebellar circuits. The spino-cerebellar tracts (SCT) in the cervical, thoracic and lumbar spinal cord have long been considered canonical neural substrates for the conveyance of internal feedback signals. Here we consider the distinct features of an indirect spino-cerebellar route, via the brainstem lateral reticular nucleus (LRN), and the implications of this pre-cerebellar "detour" for the execution and evolution of limb motor control. Both direct and indirect spino-cerebellar pathways signal spinal interneuronal activity to the cerebellum during movements, but evidence suggests that direct SCT neurons are mainly modulated by rhythmic activity, whereas the LRN also receives information from systems active during postural adjustment, reaching and grasping. Thus, while direct and indirect spinocerebellar circuits can both be regarded as internal copy pathways, it seems likely that the direct system is principally dedicated to rhythmic motor acts like locomotion, while the indirect system also provides a means of pre-cerebellar integration relevant to the execution and coordination of dexterous limb movements.
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| 18. |
- Jörntell, Henrik, et al.
(författare)
-
Functional organization of climbing fibre projection to the cerebellar anterior lobe of the rat
- 2000
-
Ingår i: Journal of Physiology. - 1469-7793. ; 522:2, s. 297-309
-
Tidskriftsartikel (refereegranskat)abstract
- 1. The input characteristics and distribution of climbing fibre field potentials evoked by electrical stimulation of various parts of the skin were investigated in the cerebellum of barbiturate anaesthetized rats. 2. Climbing fibre responses were recorded in sagittally oriented microelectrode tracks across the mediolateral width of the anterior lobe. Climbing fibres with similar response latencies and convergence patterns terminated in sagittal bands with widths of 0.5-1.5 mm. The principal organization of the anterior lobe with respect to input characteristics and locations of sagittal zones was similar to that in the cat and ferret. Hence, the sagittal bands in the rat were tentatively named the a, b, c1, c2 and d1 zones. 3. In contrast to the cat and ferret, the a zone of the rat was characterized by short latency ipsilateral climbing fibre input. Furthermore, it was divisible into a medial 'a1' zone with convergent, proximal input and a lateral 'ax' zone with somatotopically organized input. A forelimb area with similar location and input characteristics as the X zone of the cat was found, but it formed an integral part of the ax zone. A somatotopic organization of ipsilateral, short latency climbing fibre input was also found in the c1 zone. 4. Rostrally in the anterior lobe, climbing fibres activated at short latencies from the ipsilateral side of the body terminated in a somatotopically organized transverse band which extended from the midline to the lateral end of the anterior lobe. 5. The absence of the C3 and Y zones may be interpreted as a reflection of differences in the organization of the motor systems in the rat as compared with the cat. Skilled movements, which in the cat are controlled by the C1, C3 and Y zones via the anterior interposed nucleus, may in the rat be partly controlled by the ax zone via the rostrolateral part of the fastigial nucleus.
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| 19. |
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| 20. |
- Jörntell, Henrik, et al.
(författare)
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Properties of somatosensory synaptic integration in cerebellar granule cells in vivo.
- 2006
-
Ingår i: The Journal of Neuroscience. - 1529-2401. ; 26:45, s. 11786-11797
-
Tidskriftsartikel (refereegranskat)abstract
- In decerebrated, nonanesthetized cats, we made intracellular whole-cell recordings and extracellular cell-attached recordings from granule cells in the cerebellar C3 zone. Spontaneous EPSPs had large, relatively constant peak amplitudes, whereas IPSPs were small and did not appear to contribute substantially to synaptic integration at a short time scale. In many cases, the EPSPs of individual mossy fiber synapses appeared to be separable by their peak amplitudes. A substantial proportion of our granule cells had small receptive fields on the forelimb skin. Skin stimulation evoked explosive responses in which the constituent EPSPs were analyzed. In the rising phase of the response, our analyses indicated a participation of three to four different mossy fiber synapses, corresponding to the total number of mossy fiber afferents. The cutaneous receptive fields of the driven EPSPs overlapped, indicating an absence of convergence of mossy fibers activated from different receptive fields. Also in granule cells activated by joint movements did we find indications that different afferents were driven by the same type of input. Regardless of input type, the temporal patterns of granule cell spike activity, both spontaneous and evoked, appeared to primarily follow the activity in the presynaptic mossy fibers, although much of the nonsynchronized mossy fiber input was filtered out. In contrast to the prevailing theories of granule cell function, our results suggest a function of granule cells as signal-to-noise enhancing threshold elements, rather than as sparse coding pattern discriminators or temporal pattern generators.
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| 21. |
- Jörntell, Henrik, et al.
(författare)
-
Receptive field plasticity profoundly alters the cutaneous parallel fiber synaptic input to cerebellar interneurons in vivo
- 2003
-
Ingår i: The Journal of Neuroscience. - 1529-2401. ; 23:29, s. 9620-9631
-
Tidskriftsartikel (refereegranskat)abstract
- The cutaneous parallel fiber (PF) receptive fields of cerebellar stellate and basket cells in the cerebellar C3 zone in vivo are normally very small but can be dramatically enlarged by climbing fiber (CF)-dependent plasticity. To analyze the effects of this receptive field plasticity, we present for the first time whole-cell patch-clamp recordings from these interneurons during natural and electrical activation of cutaneously driven synaptic input. In "naive" interneurons, peripheral input nearly exclusively activated a few (two to eight) large PF EPSPs from a specific small skin area that overlapped the receptive field of the local CF input. After conjunctive PF and CF stimulation, numerous small and large EPSPs and ramp-like depolarizations could be activated from the entire forelimb skin. These findings therefore confirm previous suggestions that conjunctive PF and CF activation leads to a long-lasting potentiation of PF synaptic input to interneurons. The CF response, which is crucial for the induction of the PF synaptic potentiation, was strong but variable and very different from the conventional EPSPs evoked by PFs.
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| 22. |
- Jörntell, Henrik, et al.
(författare)
-
Receptive Field Remodeling Induced by Skin Stimulation in Cerebellar Neurons in vivo.
- 2011
-
Ingår i: Frontiers in Neural Circuits. - : Frontiers Media SA. - 1662-5110. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- The receptive field of a neuron reflects its function. For example, for parallel fiber (PF) inputs in C3 zone the cerebellar cortex, the excitatory and inhibitory receptive fields of a Purkinje cell (PC) have different locations, and each location has a specific relationship to the location of the climbing fiber (CF) receptive field of the PC. Previous studies have shown that this pattern of input connectivity to the PC and its afferent inhibitory interneurons can be fundamentally disrupted by applying direct electrical stimulation to the PFs, paired or unpaired with CF activation, with protocols that induce plasticity in these synapses. However, afferent fiber stimulation, which is typically used in experimental studies of plasticity, set up highly artificial input patterns at the level of the recipient cells, raising the issue that these forms of plasticity potentially may not occur under more natural input patterns. Here we used skin stimulation to set up spatiotemporally more realistic afferent input patterns in the PFs to investigate whether these input patterns are also capable of inducing synaptic plasticity using similar protocols that have previously been described for direct PF stimulation. We find that receptive field components can be added to and removed from PCs and interneurons following brief periods of skin stimulation. Following these protocols, the receptive fields of mossy fibers were unchanged. These findings confirm that previously described plasticity protocols may have a functional role also for more normal patterns of afferent input.
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| 23. |
- Jörntell, Henrik, et al.
(författare)
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Reciprocal bidirectional plasticity of parallel fiber receptive fields in cerebellar Purkinje cells and their afferent interneurons.
- 2002
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Ingår i: Neuron. - 0896-6273. ; 34:5, s. 797-806
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Tidskriftsartikel (refereegranskat)abstract
- The highly specific relationships between parallel fiber (PF) and climbing fiber (CF) receptive fields in Purkinje cells and interneurons suggest that normal PF receptive fields are established by CF-specific plasticity. To test this idea, we used PF stimulation that was either paired or unpaired with CF activity. Conspicuously, unpaired PF stimulation that induced long-lasting, very large increases in the receptive field sizes of Purkinje cells induced long-lasting decreases in receptive field sizes of their afferent interneurons. In contrast, PF stimulation paired with CF activity that induced long-lasting decreases in the receptive fields of Purkinje cells induced long-lasting, large increases in the receptive fields of interneurons. These properties, and the fact the mossy fiber receptive fields were unchanged, suggest that the receptive field changes were due to bidirectional PF synaptic plasticity in Purkinje cells and interneurons.
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| 24. |
- Jörntell, Henrik, et al.
(författare)
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Relation between cutaneous receptive fields and muscle afferent input to climbing fibres projecting to the cerebellar C3 zone in the cat
- 1996
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Ingår i: European Journal of Neuroscience. - : Wiley. - 1460-9568 .- 0953-816X. ; 8:8, s. 1769-1779
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Tidskriftsartikel (refereegranskat)abstract
- Inferior olivary cells projecting as climbing fibres to the forelimb area of the cerebellar C3 zone were investigated with respect to their cutaneous and muscle afferent input in barbiturate-anaesthetized cats. Climbing fibre responses were recorded from single cerebellar cortical Purkinje cells on natural stimulation of the skin and on electrical stimulation of nerves to m. biceps brachii, m. triceps brachii and to nine muscles acting as dorsal or palmar flexors of the paw (and, in some cases, the digits). The analysis was focused on the functional organization of convergence between cutaneous and muscle afferents onto single olivary neurons. Cutaneous receptive fields on the dorsal side of the paw and on the digits were generally associated with moderate to strong input from dorsal flexors, but little or no input from palmar flexors or proximal muscles. Receptive fields on the ventral side of the paw and forearm were associated with relatively strong input from biceps and palmar flexors. Climbing fibres with cutaneous receptive fields extending on the ulnar side of the paw and forearm usually received strong input from the triceps and moderate to strong input from dorsal flexors, whereas input from the palmar flexors was weak or lacking. In conclusion, the results indicate that the cutaneous receptive fields in many cases are associated with input from muscles the action of which would tend to move the receptive field towards a stimulus applied to the skin.
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