Experimental procedures are described that were designed to assess central motor disorders quantitatively. Initially delineated is a study of triggered ballistic movement performed in a reaction-time situation. The reciprocal triphasic EMG pattern recorded in an antagonistic muscle pair was clearly abnormal in Parkinsonian patients; increased duration, diminished synchronization of motor units, and a tendency for coactivation of agonist and antagonist muscles and for action tremor were observed. Transport time of elbow movement was prolonged, particularly in a choice reaction-time situation. Rapid, passive displacements of the forearm combined with excitability measurements of hindlimb motoneurons in monkeys revealed the existence of a transcortical loop that may contribute to increased muscle tone in Parkinsonian patients.

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PubMedDate not supplied

Sensory input to the motor fields of the agranular frontal cortex: a comparison of the precentral, supplementary motor and premotor cortex.

Arm displacements applied to the passive, but awake monkey are powerful stimuli for activating neurones in somatotopically appropriate areas of the precentral cortex. We have found that neurones in medial area 6 (SMA) and in lateral area 6 (PMC) may likewise be activated by such kinesthetic stimuli, at latencies which are only slightly longer than in area 4. Confirming previous findings, PMC neurones were sometimes also responsive to visual stimuli. The 'somatosensory' cells in the SMA were found in the microexcitable zone of the more posterior part of the SMA from where motor effects were elicited in arm and trunk muscles. These sensory neurones tended to be clustered together and they were only exceptionally excited antidromically by peduncular stimulation. Thus, somatosensory signals have access to both the PMC and SMA suggesting that both areas may be implicated in sensory-guided or sensory-triggered movements.

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PubMedDate not supplied

Responses of neurones of the pontine nuclei to stimulation of the sensorimotor, visual and auditory cortex of rats.

The aim of this study was to investigate the degree of convergence of corticofugal neurones from various cortical areas onto single neurones of the pontine nuclei (PN). Eighty-five% of the PN neurones responded to electrical stimulation of at least one of the following cortical areas: sensorimotor, visual, auditory. Slightly less than half of these neurones displayed a convergent input from two or three of functionally different cortical areas. The sensorimotor cortex, particularly the face areas, provided the most important input to the PN; stimulation of the visual cortex was less effective and stimulation of the auditory cortex rarely excited PN neurones. The electrophysiological results suggest that considerable cross-link exists between the anatomically defined cortico-pontine projection columns.

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