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Abstract:
Abstract: Lesion and brain imaging studies have implicated
the prefrontal and parietal cortices in arithmetic processing, but
do not exclude the possibility that these brain areas are also
involved in non-arithmetic operations. In the present study, we
used functional magnetic resonance imaging to explore which brain
areas contribute uniquely to numeric computation. Task difficulty
was manipulated in a factorial design by varying the number of
operands in the equation and the rate of stimulus presentation.
Both manipulations increased the number of operations to be
performed in unit time. Manipulating number of operands allowed us
to investigate the specific effect of computational complexity,
while manipulating the rate of presentation allowed us to increase
task difficulty independent of calculation. We found quantitative
changes in activation patterns in the prefrontal and parietal
cortices as well as the recruitment of additional brain regions,
including the caudate and mid-cerebellar cortex, with increasing
task difficulty. More importantly, the main effect of number of
operands was observed in the left and right parietal cortex, while
the main effect of rate of stimulus presentation was observed in
the left prefrontal cortex. Our findings indicate a dissociation in
prefrontal and parietal cortex function during arithmetic
processing and further provide the first evidence for a specific
role for the parietal cortex in arithmetic computation independent
of other processing demands.
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