Direct and Indirect Measures of Attention Indicate a Bias Toward Cues in Methamphetamine Users

Introduction:This study aims to investigate the attentional bias toward drug-related stimuli along with subjective craving after encountering such stimuli in methamphetamine users. Studies of cue reactivity have confirmed bias in attention and gaze to drug-related stimuli for most substances, but methamphetamine drugs are less studied by a direct measure such as eye tracking. Methods:Thirty male subjects in the case group (methamphetamine-users) and 36 subjects in control group (no prior drug use) participated in this study. Eye movement data were collected while subjects viewed pairs of drug-related and non-drug images in a dot-probe paradigm. Craving was assessed via a self-report questionnaire on the scale of 0 to 10 before and after the psychophysical task. Results:Analysis of eye-movement data showed meaningful gaze bias toward cue images (drug-related) for the case group. Additionally, the gaze duration on cue-images was significantly higher in the case group, while the opposite held true for the control group. The same effect was observed in the analysis of the dot probe task, that is, the mean reaction time to a probe which replaced a cue-image was significantly lower. The mean of the first-fixation measure in control group was not significantly better than chance but the percentage of first-fixation on cue images in the drug-users was meaningfully biased. Reported craving was reported as significantly greater after performing the task compared to before. Conclusion:Altogether, our results indicate an attentional bias toward drug-related cues in methamphetamine users as well as subjective craving after encountering such cues.