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  • 11
    Electronic Resource
    Electronic Resource
    Compensatory motor function of the somatosensory cortex for dysfunction of the motor cortex following cerebellar hemispherectomy in the monkey (1984)
    Springer
    Experimental brain research 56 (1984), S. 532-538 
    Details
    ISSN: 1432-1106
    Keywords: Compensatory motor function ; Somatosensory cortex ; Cerebellar hemispherectomy ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Electrical activities of the motor and somatosensory cortices preceding visually-initiated hand movements were recorded with electrodes chronically implanted on the surface and at 2.5–3.0 mm depth in the cortex of monkeys, and changes in field potentials in these cortices after cerebellar hemispherectomy were observed for many weeks. As previously reported, a unilateral cerebellar hemispherectomy including the lateral and interpositus nuclei eliminates the cerebellar-mediated superficial thalamo-cortical (T-C) responses recorded in the forelimb motor cortex contralateral to the hemispherectomy. These T-C responses normally precede the hand movement, and the operation results in the delay of movement initiation. The electrodes in the forelimb area of the contralateral primary somatosensory cortex showed an enhancement of superficial T-C responses of the somatosensory cortex for 30–40 days after the operation. The enhanced potentials preceded the delayed movement as do the cerebellar-mediated superficial T-C responses of the motor cortex in normal situations. Local cooling of the somatosensory cortex following the cerebellar hemispherectomy disturbed the reaction time movement for a few weeks after the operation. This effect was rarely encountered in normal monkeys. The present study suggests the compensatory motor function of the somatosensory cortex for the dysfunction of the motor cortex in early weeks after cerebellar hemispherectomy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237994
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  • 12
    Electronic Resource
    Electronic Resource
    Changes in cortical field potentials associated with learning processes of audio-initiated hand movements in monkeys (1988)
    Springer
    Experimental brain research 70 (1988), S. 43-49 
    Details
    ISSN: 1432-1106
    Keywords: Audio-initiated hand movement ; Cortical field potential ; Motor learning ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Field potentials on the surface and at a depth of 2.0–3.0 mm in the cerebral cortex were recorded with chronically implanted electrodes in various areas of a monkey. The potentials associated with movements in response to auditory stimuli (audio-initiated hand movement) were observed during the learning process of the movement. The monkey had to lift a lever by wrist extension within the duration of the stimulus (tone of 1000 Hz) lasting for about 900, 700 or 500 ms depending on the stage of the learning process. On the first training day, potentials appeared in the primary auditory, auditory association, prefrontal and premotor cortices of a naive monkey. The potentials of the auditory association, prefrontal and premotor cortices became less marked on the next and following days. After a few weeks of training, the potential of the auditory association cortex started to increase again, while the monkey still lifted the lever randomly. When the potential of the auditory association cortex grew to a certain extent, the monkey began to respond to the stimulus with the movement, and potentials appeared in the motor cortex in response to the auditory stimulus. After this process, the potentials in the auditory association and motor cortices gradually increased with further training, and the movement became shorter and less variable in reaction time. The potential in the motor cortex was shown to be mediated by the neocerebellum and superficial thalamo-cortical projection. The changes of potentials associated with the learning processes of audio-initiated movements were respectively compared with those of the learning processes of the visuo-initiated movement, reported previously (Sasaki and Gemba 1982), and cortical and subcortical mechanisms related to the learning process were discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271845
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  • 13
    Electronic Resource
    Electronic Resource
    Development and change of cortical field potentials during learning processes of visually initiated hand movements in the monkey (1982)
    Springer
    Experimental brain research 48 (1982), S. 429-437 
    Details
    ISSN: 1432-1106
    Keywords: Cortical field potential ; Visually initiated movement ; Motor learning ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Field potentials on the surface and at 2.5–3.0 mm depth in the cerebral cortex were recorded in various areas with chronically implanted electrodes and the potentials which preceded hand movements in response to a light stimulus were observed during the process of learning the skilled conditioned movement. A naive monkey had to lift a lever by wrist extension within duration of the light stimulus lasting for 900, 700 or 510 ms depending on the stage of the learning process. In addition to some responses in the striate gyrus, significant short-latency responses to the light stimulus appeared bilaterally in certain areas of the prefrontal and prestriate cortices at an early stage of learning in which the monkey still lifted the lever randomly, and they became gradually larger as the monkey was trained further. Short-latency responses were also often noted in the bilateral premotor cortices during an early stage of learning. When the monkey started to respond to the stimulus by the appropriate movement, early surface-positive (s-P), depth-negative (d-N) premovement potentials appeared in the forelimb motor cortex, and the responses in the premotor cortex increased in size. As the movement became faster and more skillful, late s-N, d-P premovement potentials, that are known to be mediated by the neocerebellum and superficial thalamo-cortical projections, emerged after the early s-P, d-N potentials and became more marked, larger and steeper in the forelimb motor cortex contralateral to the moving hand. All the premovement potentials in the different cortical areas thus developed into steady and constant states and remained so for many months thus maintaining their established patterns. Such successive appearances of premovement field potentials in various cortical areas were related to learning processes of the movement and the implication of these findings was discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238619
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  • 14
    Electronic Resource
    Electronic Resource
    Cortical field potentials preceding visually initiated hand movements and cerebellar actions in the monkey (1982)
    Springer
    Experimental brain research 46 (1982), S. 29-36 
    Details
    ISSN: 1432-1106
    Keywords: Premovement cortical potential ; Visually initiated movement ; Cerebellum ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cortical field potentials preceding hand movements initiated by a visual stimulus were recorded with chronically implanted electrodes in premotor, motor and somatosensory cortices of monkeys, and the influences of cerebellar hemispherectomy on cortical potentials as well as reaction time of movements were examined. As reported previously, early surface-positive, depth-negative (2.5–3 mm depth from the cortical surface) premovement potentials emerged at about 40 ms latency after onset of the light stimulus bilaterally in premotor and forelimb motor areas. Early potentials in the forelimb motor area contralateral to the moving hand were followed at about 120 ms latency by surface-negative, depth-positive late premovement potentials which are considered to be mainly composed of superficial thalamo-cortical (T-C) responses. Unilateral hemispherectomy of the cerebellum contralateral to the motor area immediately eliminated the surface-negative, depth-positive potentials. Reaction time from onset of the light stimulus to the hand movement was prolonged by 90–250 ms after cerebellar hemispherectomy. If the dentate and interpositus nuclei were also lesioned, disappearance of the late potentials and delay of the movement continued for many months. However, if the interpositus was spared, there was earlier recovery of reaction time with simultaneous reappearance of the late premovement potentials in the motor cortex. The conclusion is drawn that the cerebellar hemisphere (neocerebellum) activates the motor cortex via superficial T-C projections and participates directly in the initiation of reaction movements in response to an external stimulus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238095
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    Paper (German National Licenses)
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