Callosal Compromise Differentially Affects Conflict Processing and Attentional Allocation in Alcoholism, HIV, and Their Comorbidity

Abstract

Diffusion tensor imaging was used to study the combined effects of HIV-infection and alcoholism (ALC) on corpus callosum (CC) integrity in relation to processes of attentional allocation and conflict resolution assessed by a novel Stroop Match-to-Sample task. We tested 16 ALC, 19 HIV, 20 subjects with combined disorder and 17 controls. In ALC, low fractional anisotropy and high mean diffusivity throughout the CC correlated with poor Stroop-match performance, i.e., when the cue-color matched the color of the Stroop stimulus. By contrast, in the two HIV groups DTI relations were restricted to the genu and poor Stroop-nonmatch performance, i.e., when the cue-color was in conflict with the Stroop stimulus color. These results suggest that disruption of callosal integrity in HIV-infection and alcoholism differentially affects regionally-selective interhemispheric-dependent attentional processing. We speculate that callosal degradation in these diseases curtails the opportunity for collaboration between the two hemispheres that contributes to normal performance in HIV or alcoholic patients with higher callosal integrity.

Fig. 1

Midsagittal FA image of a 47 year old control woman. The corpus callosum was identified with a semi-automated procedure. The genu and splenium were determined geometrically and defined the borders of the body

Fig. 2

Mean ± SE of the incongruent–congruent age-corrected RTs for each group

Fig. 3

Mean ± SE of the regional FA (top) and MD (bottom), expressed as age-corrected Z-scores, for each group

Fig. 4

Correlations between regional callosal DTI measures and attentional measures within each subject group, a–c compares correlations of ALC and CTL groups, d compares the H+A and CTL groups, and e compares the HIV and CTL groups