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Role of Left Inferior Prefrontal Cortex in Retrieval of Semantic Knowledge: A Reevaluation
Sharon L. Thompson-Schill, Mark D'Esposito, Geoffrey K. Aguirre and Martha J. Farah
Proceedings of the National Academy of Sciences of the United States of America
Vol. 94, No. 26 (Dec. 23, 1997), pp. 14792-14797
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/43697
Page Count: 6
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A number of neuroimaging findings have been interpreted as evidence that the left inferior frontal gyrus (IFG) subserves retrieval of semantic knowledge. We provide a fundamentally different interpretation, that it is not retrieval of semantic knowledge per se that is associated with left IFG activity but rather selection of information among competing alternatives from semantic memory. Selection demands were varied across three semantic tasks in a single group of subjects. Functional magnetic resonance imaging signal in overlapping regions of left IFG was dependent on selection demands in all three tasks. In addition, the degree of semantic processing was varied independently of selection demands in one of the tasks. The absence of left IFG activity for this comparison counters the argument that the effects of selection can be attributed solely to variations in degree of semantic retrieval. Our findings suggest that it is selection, not retrieval, of semantic knowledge that drives activity in the left IFG.
Proceedings of the National Academy of Sciences of the United States of America © 1997 National Academy of Sciences