EFFECTS OF A RIGHT HEMIFIELD ADVANTAGE ON CROSSED UNCROSSED DIFFERENTIALS IN SIMPLE REACTION-TIME - TOWARD A NEW MODEL OF INTERHEMISPHERIC RELAY

In a meta-analysis of 16 studies employing a simple unimanual reaction time paradigm and lateralized visual stimuli, Marzi and colleagues (1 991) concluded that in normal subjects interhemispheric relay is faste r from the right to the left, than from the left to the right, hemisph ere. In a similar meta-analysis of 47 studies, Braun (1993) concluded that there are fast and slow interhemispheric channels in both directi ons that originate from each hemisphere. He proposed a model which pre dicts that a novel finding of a right field advantage, significant exp eriment-wise, as well as at each of the hands, separately, could parti ally invalidate the model proposed by Marzi et al., and help validate the one proposed by Braun, by showing that a fast interhemispheric cha nnel can be attributed to a left hemisphere origin. A simple unimanual reaction time experiment, using highly intense (743 cd/cm2) lateral s timuli, produced all of the predicted critical effects in 30 normal ri ght-handed subjects.