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Cerebral Cortex Advance Access published online on February 27, 2008
Cerebral Cortex, doi:10.1093/cercor/bhn018
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© The Author 2008. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org

Semantic Adaptation and Competition during Word Comprehension

Marina Bedny1,2,3, Megan McGill4 and Sharon L. Thompson-Schill1,2

1 Center for Cognitive Neuroscience, 2 Department of Psychology, University of Pennsylvania, PA 19104, USA, 3 Center for Non-Invasive Brain Stimulation, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215 USA, 4 School of Medicine, New York University, NY 10016, USA

Address correspondence to M. Bedny, PhD, Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, 330 Brookline Ave., KS-158, Boston, MA 02215, USA. Email: mbedny{at}bidmc.harvard.edu.

Word comprehension engages the left ventrolateral prefrontal (lVLPFC) and posterior lateral-temporal cortices (PLTC). The contributions of these brain regions to comprehension remain controversial. We hypothesized that the PLTC activates meanings, whereas the lVLPFC resolves competition between representations. To test this hypothesis, we used functional magnetic resonance imaging (fMRI) to assess the independent effects of adaptation and competition on neural activity. Participants judged the relatedness of word pairs. Some consecutive pairs contained a common ambiguous word. The same or different meanings of this word were primed (e.g., SUMMER-FAN, CEILING-FAN; ADMIRER-FAN, CEILING-FAN). Based on the logic of fMRI adaptation, trials with more semantic overlap should produce more adaptation (less activation) in regions that activate meaning. In contrast, trials with more semantic ambiguity should produce more activation in regions that resolve competition. We observed a double dissociation between activity in the PLTC and lVLPFC. LPLTC activity depended on the amount of semantic overlap, irrespective of the amount of semantic ambiguity. In contrast, lVLPFC activity depended on the amount of semantic ambiguity. Moreover, across participants the size of the competition effect as measured by errors was correlated with the size of the competition effect in the lVLPFC. We conclude that the lVLPFC is an executive mechanism within language processing.

Key Words: ambiguity • executive function • homonym • prefrontal • word comprehension


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