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Abstract:
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 this study
was to determine whether the efficiency of interhemispheric
communication (IHC), via the splenium, would correlate with the
ability to sustain attention over time in the absence of external
input in normal adults. Subjects were 32 right-handed adults
between the ages of 20 and 55. Callosal efficiency was measured on
a tachistoscopic task that required subjects to compare two lines.
On unilateral trials, both lines were on the same side of fixation.
On bilateral trials, one line was on each side of fixation. The
relative difference in reaction time for unilateral and bilateral
trials was an index of the efficiency of IHC. Subjects were divided
into two groups on the basis of this index. The ability to sustain
attention in the absence of external input was measured on a
vigilance task in which the time between target presentations
(interstimulus interval; ISI) was varied from 2 to 18 sec. Subjects
with more efficient IHC missed fewer targets on the vigilance task.
The difference between the two groups increased as ISI increased.
This suggests that individual differences in normal adults' ability
to sustain attention may be due to differences in the efficiency of
callosal transfer.
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