[Study of simple reaction time to lateralized visual stimuli]

Simple reaction time with manual response (right and left hand) to visual stimuli lateralized was studied in 20 normal subjects at 5, 20 and 35 degree in the nasal and temporal hemifields of the right eye. The reaction time was studied as a function of stimulus eccentricity. Uncrossed and crossed reaction times were examined with particular attention. No prevalence was found, neither of one hand, or of one hemisphere. The global speed of the two hemiretinas was the same, but reaction time increased as a function of stimulus eccentricity; moreover a better performance was obtained stimulating the nasal hemiretina at 35 degrees. Uncrossed reactions, considered on the whole, were faster than crossed ones (7,4 msec); the delay between crossed and uncrossed responses remained constant regardless of the degree of the visual stimuli eccentricity. The AA. concluded that such a difference is mainly dependent upon anatomical structures. The AA. also discuss several and often conflicting literature data and conclude that either the attentional model of the orienting responses as proposed by Kinsbourne, or the stimulus-response conpatibility effects, can be taken into consideration to explain some conflicting results; these results have been obtained by methods in some way different from those performed with present report (choice reaction times, absulute randomisation of the stimuli, response by crossed hands, choice verbal responses).