Cocaine abusers exhibit impairment of executive cognitive functions that are mediated by the frontal cortex. This work tested for structural (i.e., tissue composition) abnormalities that may underlie such performance deficits. Research participants were cocaine abusers (n = 14) abstinent for 20 days and a non-drug-using comparison group (n = 11), who underwent magnetic resonance imaging (T1-weighted scans of the brain). Gray matter and white matter tissue densities were determined using voxel-based morphometry with small volume correction based on a priori hypotheses derived from functional imaging of the same subjects. Cocaine abusers had significantly lower gray matter tissue density than did the non drug users in 10 of 13 small volumes analyzed in the frontal cortex [bilateral anterior cingulate gyrus (infragenual and perigenual regions) and medial orbitofrontal cortex and the lateral orbitofrontal cortex and middle/dorsal cingulate gyrus in the right hemisphere]. No group differences were found in white matter density of the frontal cortex. These results extend our previous findings of defective frontal cortical activation (indexed by cerebral blood flow) in cocaine abusers to include abnormalities in gray matter tissue density in the same frontal cortical regions.
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