Posterior and Anterior Contribution of Hand-Movement Preparation to Late CNV

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Abstract
The late part of the Contingent Negative Variation (CNV) is assumed to be a composite potential, reflecting both movement preparation and several other processes. To assess the contribution of hand-motor preparation to overall CNV, three S1-S2 experiments were performed. Replicating earlier results that have been interpreted as demonstrating hand-motor preparation, experiment 1 showed that CNV gets larger centro-parietally under speed instruction. Experiments 2 and 3 compared preparation for hand responses (key-press) to preparation for ocular responses (saccades) varying the effector system either between blocks (exp. 2) or between trials (exp. 3) and also comparing these preparation situations to no preparation (exp. 3). Hand-motor preparation was reflected in CNV getting larger fronto-centrally, with this topography being significantly different from the effect in experiment 1. Thus, two different kinds of motor preparation appear to be reflected by CNV. One kind may consist of assembling and maintaining the stimulus-response links appropriate to the expected S2 patterns, the other is for activating the hand-motor area. These two motor contributions to CNV might reflect the two aspects of the parieto-frontal motor system.