[Electrophysiological analysis of the blink reflex during hemiplegia due to hemispheric lesions]

Electrical stimulation of the supra-orbital nerve induces at the same threshold an early reflex reaction in the ipsilateral orbicular muscle and a delayed bilateral reflex response. These reflex activities are modified bilaterally by unilateral hemispheric lesions. Reactions on the hemiplegic side are reduced in amplitude, unlike the responses on the "healthy side" which are facilitated. Adaptation of the reflexogenous threshold of the delayed responses to repeated stimulation is also irregular; cumulative depression occurs earlier on the hemiplegic side, the responses on the "healthy side", on the other hand, show less habituation or a total absence of it. These electrophysiological findings agree with experimental results concerning the influence of cortical structures on the activity of the nuclei of the brain stem. They also, by analogy with the results of research carried out on the limbs, support the tactile origin of the two constituents of the blink reflex.