Individual differences in callosal efficiency: correlation with attention

Previous studies of clinical populations and normal children have suggested that the efficiency of callosal transfer correlates with the ability to sustain attention. The purpose of the present study was to determine whether the same might be true for normal adults. Subjects were 42 right-handed adults. The efficiency of the transfer via the anterior callosum was assessed on a bimanual coordination task. The efficiency of the posterior callosum was measured on a tachistoscopic task that required subjects to compare two lines when both were presented either to the same visual field or to opposite visual fields. Sustained attention was measured on a vigilance task in which the time between target presentations (ISI) was varied. Performance on the bimanual task correlated with the ability to sustain attention over the entire 20 min of the vigilance task. The efficiency of the posterior callosum was related to the ability to detect targets that occurred after relatively long ISIs.