THE CONTINGENT NEGATIVE-VARIATION IN A CHOICE REACTION-TIME-TASK

Ten normal human subjects performed isometric contractions up to a fixed force level, which had to be attained at two different speeds, in a choice reaction time task. Force production speed was indicated by an instruction stimulus, which was either inserted at the warning stimulus (Precue condition) or at the response stimulus (No-Precue condition). These conditions were used to test the hypothesis that the late wave of the CNV consists of movement- and stimulus-preceding negativities. The latter condition was expected to produce larger CNV late wave amplitudes because of the anticipation of the additional informative stimulus. The results were in agreement with this prediction. Two components, one centrally dominant and the other frontally dominant, were distinguished in the CNV. The central component is suggested to be identical to the Readiness Potential and the frontal component is discussed in terms of stimulus anticipation and task demands.