Influence of saccades on manual reactions--a reaction time and VEP study.

Experiments were performed to investigate the retardation of motor reactions, triggered immediately after saccadic eye movements, by comparing VEP latencies and manual reaction times. As visual stimuli grating patterns of different spatial frequencies were used. They were presented during continuous fixation ("resting eye" condition) as well as shortly after a saccade ("saccadic" condition) with different onset delays (25, 50, 100, 150 msec), in order to determine the influence of saccades on VEP latencies and on manual reaction times. Compared with the reaction times in the "resting eye" condition, the postsaccadic reaction times were much prolonged whereas the respective VEP latencies are almost unchanged. Thus an inhibitory interaction of different motor responses (i.e. saccadic eye movements and manual reactions in this study) at higher levels of the afferent system or at the motor control site is postulated. This result has been confirmed for stimuli of different spatial frequencies.