White matter fiber compromise contributes differentially to attention and emotion processing impairment in alcoholism, HIV-infection, and their comorbidity

Abstract

Alcoholism (ALC) and HIV-1 infection (HIV) each affects emotional and attentional processes and integrity of brain white matter fibers likely contributing to functional compromise. The highly prevalent ALC+HIV comorbidity may exacerbate compromise. We used diffusion tensor imaging (DTI) and an emotional Stroop Match-to-Sample task in 19 ALC, 16 HIV, 15 ALC+HIV, and 15 control participants to investigate whether disruption of fiber system integrity accounts for compromised attentional and emotional processing. The task required matching a cue color to that of an emotional word with faces appearing between the color cue and the Stroop word in half of the trials. Nonmatched cue-word color pairs assessed selective attention, and face-word pairs assessed emotion. Relative to controls, DTI-based fiber tracking revealed lower inferior longitudinal fasciculus (ilf) integrity in HIV and ALC+HIV and lower uncinate fasciculus (uf) integrity in all three patient groups. Controls exhibited Stroop effects to positive face-word emotion, and greater interference was related to greater callosal, cingulum and ilf integrity. By contrast, HIV showed greater interference from negative Stroop words during color-nonmatch trials, correlating with greater uf compromise. For face trials, ALC and ALC+HIV showed greater Stroop-word interference, correlating with lower cingulate and callosal integrity. Thus, in HIV, conflict resolution was diminished when challenging conditions usurped resources needed to manage interference from negative emotion and to disengage attention from wrongly cued colors (nonmatch). In ALC and ALC+HIV, poorer callosal integrity was related to enhanced emotional interference suggesting curtailed interhemispheric exchange needed between preferentially right-hemispheric emotion and left-hemispheric Stroop-word functions.

Figure 1. Emotional Stroop Paradigm

The task was to match the color of a color cue to that of a target stimulus (word or XXXXX) by pressing a YES-key for color matches and a NO-key for color nonmatches. The task had the following color matching conditions: 1) no face–letter string (baseline); 2) no face–word HAPPY; 3) no face–word ANGRY; 4) happy face–letter string; 5) angry face–letter string; 6) happy face–word HAPPY; 7) angry face–word ANGRY. Face stimuli were selected from the MacBrain Face Stimulus Set (http://www.macbrain.org/resources.htm). Development of the MacBrain Face Stimulus Set was overseen by Nim Tottenham and supported by the John D. and Catherine T. MacArthur Foundation Research Network on Early Experience and Brain Development.

Figure 2. Behavioral results

A. Mean reaction times (RT) and standard error bars for matching colors between cue and letter string (XXXXX) (baseline) for color-matches and nonmatches, trials without and with faces (happy and angry), for each study group: healthy controls (CTL), patients with alcoholism (ALC), HIV infection (HIV) and comorbid disorder (ALC+HIV). Note that baseline color-matching RTs for each condition did not significantly differ between groups. B. Emotional Stroop effects: Difference RTs between word trials and baseline trials for the Stroop words HAPPY and ANGRY, for trials with and without emotional faces for each study group, and separately for match and nonmatch trials.

Figure 3. Structure-function relationships

Correlations between emotional Stroop effects and fiber integrity measures for each study group: healthy controls (CTL), patients with alcoholism (ALC), HIV infection (HIV), and comorbid disorder (ALC+HIV).