Enhanced choice for viewing cocaine pictures in cocaine addiction

Abstract

Background: Individuals with cocaine use disorder (CUD) chose cocaine over nondrug rewards. In two newly designed laboratory tasks with pictures, we document this modified choice outside of a cocaine administration paradigm.

Methods: Choice for viewing cocaine, pleasant, unpleasant, or neutral pictures--under explicit contingencies (choice made between two fully visible side-by-side images) and under more implicit contingencies (selections made between pictures hidden under flipped-over cards)--was examined in 20 CUD and 20 matched healthy control subjects. Subjects also provided self-reported ratings of each picture's pleasantness and arousal.

Results: Under both contingencies, CUD subjects chose to view more cocaine pictures than control subjects, group differences that were not fully explained by the self-reported picture ratings. Furthermore, whereas CUD subjects' choice for viewing cocaine pictures exceeded choice for viewing unpleasant pictures (but did not exceed choice for viewing pleasant pictures, in contrast to their self-reported ratings), healthy control subjects avoided viewing cocaine pictures as frequently as, or even more than, unpleasant pictures. Finally, CUD subjects with the most cocaine viewing selections, even when directly compared with selections of the pleasant pictures, also reported the most frequent recent cocaine use.

Conclusions: Enhanced drug-related choice in cocaine addiction can be demonstrated even for nonpharmacologic (pictorial) stimuli. This choice, which is modulated by alternative stimuli, partly transcends self-reports (possibly indicative of a disconnect in cocaine addiction between self-reports and objective behavior) to provide an objective marker of addiction severity. Neuroimaging studies are needed to establish the neural underpinnings of such enhanced cocaine-related choice.

Conflict of interest statement

Disclosure/Conflict of Interest

The authors report no biomedical financial interests or potential conflicts of interest.

Figures

Figure 1

Experimental paradigm for the ‘explicit’ task. The explicit task included training and 1 block, consisting of 70 trials. Two sample trials (A and B) are displayed. At trial onset, two side-by-side images appeared (this default screen remained for the 5000 msec duration unless subjects executed a response). Continuous button pressing enlarged the corresponding image, as shown in both examples (A: right picture; B: left picture, both indicated by red box), for the 5000 msec trial duration; no response (for 500 msec) after initial response returned the side-by-side display. Each trial onset was preceded by a 1500 msec fixation cross to separate trials (not depicted in figure).

Figure 2

Experimental paradigm for the ’implicit’ task. (A) Overall design, consisting of training (TR) and 4 runs (R). (B) Breakdown of deck identity across the runs: each run contained four decks that were comprised of mostly (87%) cocaine (C), pleasant (P), unpleasant (U), or neutral (N) pictures. Deck location did not repeat across the runs. (C) Sample trials: in each trial within a run, subjects had to choose one of four flipped-over cards; a run terminated after eight total choices from the same deck (maximum of 29 selections). Subjects pressed one of four buttons corresponding to their chosen deck. After the image appeared for 2000 msec, the choice screen reappeared, and subjects made another selection. Here in two sample trials, decks 3 and 2 are selected, respectively, indicated by the red box. The choice screen remained until a selection was made.

Figure 3

Results of the picture ratings for (A) pleasantness and (B) arousal for each of the four picture types (pleasant, unpleasant, neutral, and cocaine) for individuals with cocaine use disorders (CUD; N=20), as compared to healthy comparison subjects (HC; N=19; one control subject did not complete picture ratings due to keypad malfunction). For both (A) and (B), error bars represent standard error of the mean. Between-group comparisons are indicated by light, solid lines; within-group comparisons for CUD are indicated by heavy, solid lines; and within-group comparisons for HC are indicated by broken lines; * p<0.05; all comparisons shown directly pertain to our a priori hypotheses. Supplementary Table 1 presents all significant comparisons (including comparisons not displayed in Figure 3), as well as means and standard errors for both picture ratings.

Figure 3

Results of the picture ratings for (A) pleasantness and (B) arousal for each of the four picture types (pleasant, unpleasant, neutral, and cocaine) for individuals with cocaine use disorders (CUD; N=20), as compared to healthy comparison subjects (HC; N=19; one control subject did not complete picture ratings due to keypad malfunction). For both (A) and (B), error bars represent standard error of the mean. Between-group comparisons are indicated by light, solid lines; within-group comparisons for CUD are indicated by heavy, solid lines; and within-group comparisons for HC are indicated by broken lines; * p<0.05; all comparisons shown directly pertain to our a priori hypotheses. Supplementary Table 1 presents all significant comparisons (including comparisons not displayed in Figure 3), as well as means and standard errors for both picture ratings.

Figure 4

(A) Results of the ‘explicit’ task, showing total button presses for each of the five picture categories (pleasant, unpleasant, neutral, cocaine, and blank) for individuals with cocaine use disorders (CUD; N=20), as compared to healthy comparison subjects (HC; N=20). (B) Results of the ‘implicit’ task, showing total picture selections for each of the four picture categories for the same two subject groups. For both (A) and (B), error bars represent standard error of the mean. Between-group comparisons are indicated by light, solid lines; within-group comparisons for CUD are indicated by heavy, solid lines; and within-group comparisons for HC are indicated by broken lines; * p<0.05; all comparisons shown directly pertain to our a priori hypotheses. Supplementary Table 1 presents all significant comparisons (including comparisons not displayed in Figure 4), as well as means and standard errors for both choice tasks.

Figure 4

(A) Results of the ‘explicit’ task, showing total button presses for each of the five picture categories (pleasant, unpleasant, neutral, cocaine, and blank) for individuals with cocaine use disorders (CUD; N=20), as compared to healthy comparison subjects (HC; N=20). (B) Results of the ‘implicit’ task, showing total picture selections for each of the four picture categories for the same two subject groups. For both (A) and (B), error bars represent standard error of the mean. Between-group comparisons are indicated by light, solid lines; within-group comparisons for CUD are indicated by heavy, solid lines; and within-group comparisons for HC are indicated by broken lines; * p<0.05; all comparisons shown directly pertain to our a priori hypotheses. Supplementary Table 1 presents all significant comparisons (including comparisons not displayed in Figure 4), as well as means and standard errors for both choice tasks.

Figure 5

Scatterplots in the CUD (N=20) showing associations between cocaine selection and drug use variables on the ‘implicit’ task: (A) correlations between cocaine selection and number of cocaine use days in the past 30 days; and (B) cocaine>pleasant selection and number of cocaine use days in the past 30 days. Because these analyses used Spearman correlations, all scores and drug use scores are presented as ranks.