[Reaction time and interhemispheric interaction].

The study was made on healthy adult subjects. The reaction time of the hand (RT) was measured under two conditions: 1) the choice of reaction (right or left hand) is determined by the nature of the warning stimulus; 2) decision on the choice is taken, depending on the second, trigger stimulus. Stimuli are presented at random sequences to different visual fields. The reaction time to the visual signal presented to the visual field ipsilateral to the hand is significantly shorter (by 15 to 26 msec) than to the stimulus in the contralateral visual field. In a simple motor reaction, when no discrimination of trigger stimulus and the decision on the choice of reaction is required, a hemispheric asymmetry of reaction time is manifested: the left hemisphere only responds differently to direct visual stimulation and to that mediated through the contralateral hemisphere.