Movement and stimulus preceding negativity.

After a short description of the different premovement potentials it is suggested that readiness potentials (RPs) recorded over different cortical motor areas reflect different functions. Then it is proposed that the late wave of the contingent negative variation (CNV) is a composite of a RP and a stimulus preceding negativity (SPN). Arguments for the existence of a non-motoric SPN are given, based upon our recent experiments. Next, it is suggested that a SPN is found preceding at least three different kinds of stimuli. Finally, it is stated that motor preparation and stimulus anticipation are different processes, reflected in a different distribution of the accompanying Slow Waves and an all or none accompanying change in reflex amplitudes.