The Journal of Neuroscience, March 12, 2008, 28(11):2912-2918; doi:10.1523/JNEUROSCI.2295-07.2008
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Behavioral/Systems/Cognitive
Structural Organization of the Corpus Callosum Predicts the Extent and Impact of Cortical Activity in the Nondominant Hemisphere
Mary Colvin Putnam,
Gagan S. Wig,
Scott T. Grafton,
William M. Kelley, and
Michael S. Gazzaniga
Department of Psychological and Brain Sciences, Center for Cognitive Neuroscience, Dartmouth College, Hanover, New Hampshire 03755
Correspondence should be addressed to Dr. Mary Colvin Putnam at her present address, Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, 1 Bowdoin Square, 7th Floor, Boston, MA 02114. Email: mputnam1{at}partners.org
Diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) were combined to examine the relationship between callosal organization and cortical activity across hemispheres. Healthy young adults performed an incidental verbal encoding task (semantic judgments on words) while undergoing fMRI. Consistent with previous studies, the verbal encoding task was associated with left-lateralized activity in the inferior prefrontal cortex (LIPFC). When subjects were divided into two groups based on fractional anisotropy (FA) values in the anterior corpus callosum (DTI), individuals with low anterior callosal FA were found to exhibit greater activity in a homologous region within the right inferior prefrontal cortex (RIPFC) relative to those with high anterior callosal FA. Interestingly, whereas the magnitude of RIPFC activity did not negatively impact subsequent verbal memory performance for individuals with low anterior callosal FA, greater RIPFC activity during verbal encoding was associated with poorer subsequent memory performance for individuals with high anterior callosal FA. Together, these findings provide novel evidence that individual differences in callosal organization are related to the extent of nondominant cortical activity during performance during a lateralized task, and further, that this relationship has consequences on behavior.
Key words: corpus callosum; laterality; hemispheric asymmetry; memory; individual differences; neuroimaging
Received May 18, 2007;
revised Dec. 12, 2007;
accepted Jan. 7, 2008.
Correspondence should be addressed to Dr. Mary Colvin Putnam at her present address, Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, 1 Bowdoin Square, 7th Floor, Boston, MA 02114. Email: mputnam1{at}partners.org