| 1. |
- Kinoshita, Masaharu, et al.
(författare)
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Genetic dissection of the circuit for hand dexterity in primates
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 487:7406, s. 235-U1510
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Tidskriftsartikel (refereegranskat)abstract
- It is generally accepted that the direct connection from the motor cortex to spinal motor neurons is responsible for dexterous hand movements in primates(1-3). However, the role of the 'phylogenetically older' indirect pathways from the motor cortex to motor neurons, mediated by spinal interneurons, remains elusive. Here we used a novel double-infection technique to interrupt the transmission through the propriospinal neurons (PNs)(4-6), which act as a relay of the indirect pathway in macaque monkeys (Macaca fuscata and Macaca mulatta). The PNs were double infected by injection of a highly efficient retrograde gene-transfer vector into their target area and subsequent injection of adeno-associated viral vector at the location of cell somata. This method enabled reversible expression of green fluorescent protein (GFP)-tagged tetanus neurotoxin, thereby permitting the selective and temporal blockade of the motor cortex-PN-motor neuron pathway. This treatment impaired reach and grasp movements, revealing a critical role for the PN-mediated pathway in the control of hand dexterity. Anti-GFP immunohistochemistry visualized the cell bodies and axonal trajectories of the blocked PNs, which confirmed their anatomical connection to motor neurons. This pathway-selective and reversible technique for blocking neural transmission does not depend on cell-specific promoters or transgenic techniques, and is a new and powerful tool for functional dissection in system-level neuroscience studies.
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| 2. |
- Alstermark, Bror, et al.
(författare)
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Circuits for skilled reaching and grasping
- 2012
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Ingår i: Annual Review of Neuroscience. - Palo alto : ANNUAL REVIEWS. - 1545-4126. - 9780824324353 ; , s. 559-578
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Bokkapitel (refereegranskat)abstract
- From an evolutionary perspective, it is clear that basic motor functions such as locomotion and posture are largely controlled by neural circuitries residing in the spinal cord and brain-stem. The control of voluntary movements such as skillful reaching and grasping is generally considered to be governed by neural circuitries in the motor cortex that connect directly to motoneurons via the corticomotoneuronal (CM) pathway. The CM pathway may act together with several brain-stem systems that also act directly with motoneurons. This simple view was challenged by work in the cat, which lacks the direct CM system, showing that the motor commands for reaching and grasping could be mediated via spinal interneurons with input from the motor-cortex and brain-stem systems. It was further demonstrated that the spinal interneurons mediating the descending commands for reaching and grasping constitute separate and distinct populations from those involved in locomotion and posture. The aim of this review is to describe populations of spinal interneurons that are involved in the control of skilled reaching and grasping in the cat, monkey, and human.
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| 3. |
- Alstermark, Bror, et al.
(författare)
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Premotoneuronal and direct corticomotoneuronal control in the cat and macaque monkey.
- 2002
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Ingår i: Advances in Experimental Medicine and Biology. - 0065-2598 .- 2214-8019. ; 508, s. 281-97
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Tidskriftsartikel (refereegranskat)abstract
- The literature on premotoneuronal and direct corticomotoneuronal (CM) control in the cat and macaque monkey is reviewed. The available experimental findings are not in accordance with a recently proposed hypothesis that direct CM connections have "replaced" the premotoneuronal pathways. Instead, we propose that premotoneuronal CM control plays an important role in motor control also in primates and that the direct CM connection has been added during phylogeny.
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| 4. |
- Isa, Tadashi, et al.
(författare)
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Direct and indirect cortico-motoneuronal pathways and control of Hand/Arm movements
- 2007
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Ingår i: PHYSIOLOGY. - : American Physiological Society. - 1548-9213 .- 1548-9221. ; 22, s. 145-152
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies from our group have demonstrated the existence of a disynaptic excitatory cortico-motoneuronal (CM) pathway in macaque monkeys via propriospinal neurons in the midcervical segments. Results from behavioral studies with lesion of the direct pathway suggest that the indirect CM pathway can mediate the command for dexterous finger movements.
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| 5. |
- 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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| 6. |
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| 7. |
- Nishimura, Yukio, et al.
(författare)
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Time-dependent central compensatory mechanisms of finger dexterity after spinal cord injury.
- 2007
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Ingår i: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 318:5853, s. 1150-5
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Tidskriftsartikel (refereegranskat)abstract
- Transection of the direct cortico-motoneuronal pathway at the mid-cervical segment of the spinal cord in the macaque monkey results in a transient impairment of finger movements. Finger dexterity recovers within a few months. Combined brain imaging and reversible pharmacological inactivation of motor cortical regions suggest that the recovery involves the bilateral primary motor cortex during the early recovery stage and more extensive regions of the contralesional primary motor cortex and bilateral premotor cortex during the late recovery stage. These changes in the activation pattern of frontal motor-related areas represent an adaptive strategy for functional compensation after spinal cord injury.
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| 8. |
- Perfiliev, Sergei, 1957, et al.
(författare)
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Reflexive limb selection and control of reach direction to moving targets in cats, monkeys, and humans.
- 2010
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Ingår i: Journal of neurophysiology. - : American Physiological Society. - 1522-1598 .- 0022-3077. ; 104:5, s. 2423-32
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Tidskriftsartikel (refereegranskat)abstract
- When we reach for an object, we have to decide which arm to use and the direction in which to move. According to the established view, this is voluntarily controlled and programmed in advance in time-consuming and elaborate computations. Here, we systematically tested the motor strategy used by cats, monkeys, and humans when catching an object moving at high velocity to the left or right. In all species, targets moving to the right selectively initiated movement of the right forelimb and vice versa for targets moving to the left. Movements were from the start directed toward a prospective target position. In humans, the earliest onset of electromyographic activity from start of motion of the target ranged from 90 to 110 ms in different subjects. This indicates that the selection of the arm and specification of movement direction did not result from the subject's voluntary decision, but were determined in a reflex-like manner by the parameters of the target motion. As a whole the data suggest that control of goal-directed arm movement relies largely on an innate neuronal network that, when activated by the visual signal from the target, automatically guides the arm throughout the entire movement toward the target. In the view of the present data, parametric programming of reaching in advance seems to be superfluous.
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| 9. |
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