The effect of percutaneous motor cortex stimulation on H reflexes in muscles of the arm and leg in intact man.

摘要: The technique of electrical stimulation the brain via scalp electrodes has been used to activate corticospinal pathways in intact man. intensity was adjusted be below threshold necessary evoke a direct electromyographic response when muscles being tested were totally relaxed. Changes spinal cord excitability measured using H-reflex (monosynaptic) testing. By this means it found that subthreshold can produce descending volley even absence muscle response. time course changes evaluated by evoking test H reflexes at different intervals relative stimulus. In wrist and finger flexor seven subjects, single shock produced an initial peak facilitation reflex which on average lasted for 2.5 ms. end marked return towards basal levels one occasion frank inhibition. It is suggested arrival motoneurones monosynaptic excitatory post-synaptic potentials (e.p.s.p.s) truncated subsequent disynaptic inhibitory (i.p.s.p.s). followed second phase reflex. weaker, more variable longer lasting (from 5 20 ms) than first phase. stimulus required effect same phases facilitation. Several possible explanations are discussed mechanism responsible late long-lasting two subjects extensor studied. similar flexors except inhibition both subjects. subject thenar tibialis anterior studied behaved similarly muscles. Effects soleus five these contrast other studied, event This also could seen preceding usual period averaged rectified surface electromyogram (e.m.g.) records stimuli given during weak voluntary activation soleus.(ABSTRACT TRUNCATED AT 400 WORDS)