Farmer, Simon Francis; (1991) The central and reflex control of movements studied during health and disease in man. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Electromyographic studies have been made of normal and abnormal motor control in man. Time and frequency domain analyses have been performed on the firing of motor units recorded during voluntary contractions in normal subjects and patients with neurological conditions. In normal subjects, coherence spectra show significant peaks in the frequency ranges 1-12 Hz and 16-32 Hz. Comparison of the results of time and frequency domain analysis, suggests that peaks in the coherence spectra reflect the frequency content of common synaptic inputs to motoneurones. Spectral components in the frequency range 16-32 Hz are likely to reflect the frequency content of activity in branched common-stem presynaptic inputs. Studies utilizing peripheral afferent stimulation, indicate that the main determinant of a peak in the motor unit coherence spectra is the presence of a periodically discharging common input. Motor unit recordings from stroke patients suggest that short-term synchronization and coherence in the 16-32 Hz band require the integrity of the corticospinal tract. Bilateral electromyographic recordings have been made from the hand muscles of an adult patient with mirror movements. Analysis of these data suggests that the corticospinal tract has branched to innervate the motoneurones on both left and right sides of the spinal cord. Furthermore, in this patient, the unusual distribution of the long-latency components of the stretch and cutaneous reflexes strongly supports the hypothesis that they are mediated transcortically. Central nervous reorganisation following injury has been investigated in adult stroke patients and in children with cerebral palsy. Following central nervous lesions in the adult, limited changes in the activity and organisation of presynaptic inputs to motoneurones occur. The neural plasticity that follows unilateral central nervous lesions acquired at or before birth is much more marked and may involve branching of axons from the intact corticospinal tract in order innervate motoneurones bilaterally.

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