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Abstract:
Our goal was to directly test Kosslyn's hypothesis (1987)
that the left hemisphere is more efficient at processing
categorical spatial relationships and the right hemisphere is more
efficient at processing coordinate spatial relationships by
comparing error rates on visuospatial tasks performed during left
versus right hemisphere deactivation. We analyzed data from 134
patients who underwent temporary hemispheric deactivation via
intracarotid sodium amobarbital injection as part of an evaluation
of intractable epilepsy. During hemispheric deactivation, in
addition to tests of language and memory, subjects were asked to
perform two categorical and three coordinate visuospatial tasks.
Stimuli were stratified by task difficulty. With high task
difficulty, subjects made more categorical errors during left
hemisphere deactivation and more coordinate errors during right
hemispheric deactivation, consistent with Kosslyn's hypothesis.
With low task difficulty, a left hemisphere processing advantage
was observed for both categorical and coordinate tasks. Thus our
results confirm a right hemispheric advantage for demanding
coordinate processing tasks, but indicate that the left hemisphere
may be better at easier coordinate tasks.
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