Contingent negative variation in processes of expectancy, motor preparation and time estimation.

The contingent Negative Variation (CNV) was compared in four paradigms inducing distinct processes. All paradigms comprised empty intervals of 4 sec bounded by two 100 msec stimuli (S1 and S2) or by S1 and the response (a button press). In paradigm ID (Intensity Discrimination), the S1-S2 interval was followed, after another delay, by a choice response depending on the intensity of S2. In paradigm RT (Reaction Time), the S1-S2 interval was followed by a simple reaction time. In paradigm TP (Time Production), the subjects had to produce a response 4 sec after S1. In paradigm TR (Time Reproduction), the duration of the S1-S2 interval was estimated by the subjects and was to be reproduced after S2. Electrodes were placed on Cz, Fz and Pz in 12 human subjects. The largest CNVs were obtained in paradigm TR. Motor preparation before S2 had no effect on CNV amplitude. Discussion focuses upon the relations between CNV, temporal processes and activation.