Attentional bias for nondrug reward is magnified in addiction

Abstract

Attentional biases for drug-related stimuli play a prominent role in addiction, predicting treatment outcomes. Attentional biases also develop for stimuli that have been paired with nondrug rewards in adults without a history of addiction, the magnitude of which is predicted by visual working-memory capacity and impulsiveness. We tested the hypothesis that addiction is associated with an increased attentional bias for nondrug (monetary) reward relative to that of healthy controls, and that this bias is related to working-memory impairments and increased impulsiveness. Seventeen patients receiving methadone-maintenance treatment for opioid dependence and 17 healthy controls participated. Impulsiveness was measured using the Barratt Impulsiveness Scale (BIS-11; Patton, Stanford, & Barratt, 1995), visual working-memory capacity was measured as the ability to recognize briefly presented color stimuli, and attentional bias was measured as the magnitude of response time slowing caused by irrelevant but previously reward-associated distractors in a visual-search task. The results showed that attention was biased toward the distractors across all participants, replicating previous findings. It is important to note, this bias was significantly greater in the patients than in the controls and was negatively correlated with visual working-memory capacity. Patients were also significantly more impulsive than controls as a group. Our findings demonstrate that patients in treatment for addiction experience greater difficulty ignoring stimuli associated with nondrug reward. This nonspecific reward-related bias could mediate the distracting quality of drug-related stimuli previously observed in addiction.

Figure 1

Sequence of events and time course for a trial during the training phase (A) and test phase (B) of the visual search task. During the training phase, patients and controls searched for a target circle that was unpredictably red or green, and received a monetary reward for correctly reporting the orientation of a bar contained within the target. During the test phase, participants searched for a target defined as the unique shape (e.g., diamond among circles) and no monetary rewards were provided. On a subset of the trials, one of the non-target shapes was rendered in the color of a formerly reward-predictive target (i.e., red or green), which served as the reward-associated distractor.

Figure 2

Response time across the three distractor conditions in the test phase for patients and controls. There was a main effect of distractor condition in which participants were significantly slower to report the target when a high-value distractor was present compared to when no distractor was present (“absent”), indicating value-driven attentional capture (**p < .001). The magnitude of this slowing was significantly greater in the patients than in the controls (*p < .01), indicating greater susceptibility to attentional capture by previously reward-associated stimuli. Error bars reflect the within-subjects standard error of the mean.

Figure 3

Correlation between value-driven attentional capture (slowing in RT caused by the high-value distractor) and visual working memory capacity separately for patients (r = −.697, p = .002) and controls (r = −.046, p = .860).