A comparison of interhemispheric transmission times as measured by verbal and manual reaction time

Interhemispheric transmission times (IHTTs) were calculated for 33 right-handed subjects. Verbal and manual response times (RTs) were recorded to visual stimuli exposed in either the left or right visual fields (LF, RF) for 50 msec. Each subject received 15 stimuli (dots) in the LF (1.5 degrees to the left of fixation), 15 stimuli in the RF, and 15 blank trials in both the verbal and manual response condition. IHTTs were calculated for each subject by subtracting the mean RF RT (I.E., uncrossed path) from the means LF RT (i.e., crossed path). Results indicated a nonsignificant IHTT obtained under the manual response condition of 5 msec and a highly significant IHTT obtained under the verbal response condition of 20 msec. While no significant correlation was found between IHTTs obtained under both response conditions, high correlations were found between component RT measures (i.e., manual RF RT, manual LF RT, verbal RF RT, and verbal LF RT). Thus, IHTT is independent of simple RT.