The contingent negative variation and the excitability of the spinal monosynaptic reflex

A method is described which permits simultaneous measurement of changes in slow electroencephalographic potentials (Contingent Negative Variation-CNV) and the excitability of the spinal monosynaptic arc (H reflex) during the foreperiod of a simple reaction time experiment. Data from 11 normal subjects show that during the development of the CNV there is an augmentation of the amplitude of the H-reflex. It is suggested that the two phenomena are controlled by a common subcortical structure.