Tactual and auditory vigilance in split-brain man.

Two studies are reported of tactual and auditory vigilance performance in patients with a split-brain or partial commissurotomy to examine the attentional behaviour of the right and left hemisphere, and to identify defects in attention which may be related to the division of the cerebral commissures. The performance of the right hemisphere on all tasks of sustained attention so far studied was substantially better than that of the left. Considerable depletion of concentration was observed for the total split-brain group but not in patients with partial commissurotomy. One of the more unusual phenomena of the split-brain condition is that gaps of attention, often lasting many seconds, occur predominantly on the left hemisphere. The switch to a different type of signal on the same hemisphere does not stop them but the switching of signals from one hemisphere to another does. The defect is interpreted as a failure of attention peculiar to the individual hemisphere under test.