Response latencies and event-related potentials during the gap paradigm using saccadic responses in human subjects.

An experiment was conducted in naive human subjects to measure the time benefits of the latencies of saccadic eye movements to peripheral targets when the offset of a central fixation point precedes the switching on of the peripheral target by 200 ms. Naive subjects produced a shift advancement of the eye movement latencies to the targets with respect to when there is no such temporal gap. Simultaneously, the event-related potentials produced by visual stimuli and saccadic eye movements were recorded. The switching on of the central fixation point induced a negative component that could be considered a contingent negative variation. Subsequently, in the control non-gap condition visual evoked potentials and P300 appear. The temporal gap paradigm induced offset visual-evoked potentials and a frontal negativity; it also induced a higher P300 than the non-gap condition. The saccadic ERPs also showed a frontal negativity preceding the saccade during the gap condition. The results suggest that fast regular saccades during the gap paradigm occur by a priming of premotor and motor frontal circuits indexed by the recorded negativity during the gap paradigm.