1 Multimodal Functional Imaging Lab, Department of Physics and PERFORM Centre, Concordia University, Montreal, Quebec,Canada.
2 Multimodal Functional Imaging Lab, Biomedical Engineering Department, McGill University, Montreal, Quebec, Canada.
3 Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran,Iran.
4 Research Center for Biomedical Technology and Robotics, Institute of Advanced Medical Technologies, Tehran University of Medical Sciences, Tehran,Iran.
5 Department of Psychiatry, Icahn School of Medicine, Mount Sinai, New York, USA.
6 Department of Neuroscience, Icahn School of Medicine, Mount Sinai, New York, USA.
7 Department of Electrical Engineering, Shohadaye Hoveizeh Campus of Technology, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
8 Department of Nursing, Razi School of Nursing and Midwifery, Kerman University of Medical Sciences, Kerman, Iran.
9 Laureate Institute for Brain Research, Tulsa, Oklahoma, USA.
10 Iranian National Center for Addiction Studies, Tehran University of Medical Sciences, Tehran, Iran.
11 Department of Cognitive Psychology, Institute for Cognitive Sciences Studies, Tehran, Iran.
12 Neuroscience and Addiction Studies Department, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran (Dr Noroozi).

Background: Although transcranial direct current stimulation (tDCS) has shown to potentially mitigate drug craving and attentional bias to drug-related stimuli, individual differences in such modulatory effects of tDCS are less understood. In this study, we aimed to investigate a source of the inter-subject variability in the tDCS effects that can be useful for tDCS-based treatments of individuals with methamphetamine (MA) use disorder (IMUD).

Methods: Forty-two IMUD (all male) were randomly assigned to receive a single-session of either sham or real bilateral tDCS (anodal right/cathodal left) over the dorsolateral prefrontal cortex. The tDCS effect on MA craving and biased attention to drug stimuli were investigated by quantifying EEG-derived P3 (a measure of initial attentional bias) and late positive potential (LPP; a measure of sustained motivated attention) elicited by these stimuli. To assess the association of changes in P3 and LPP with brain connectivity network (BCN) topology, the correlation between topology metrics, specifically those related to the efficiency of information processing, and the tDCS effect was investigated.

Results: The P3 amplitude significantly decreased following the tDCS session, whereas the amplitudes increased in the sham group. The changes in P3 amplitudes were significantly correlated with communication efficiency measured by BCN topology metrics (r = -0.47, P = .03; r = -0.49, P = .02). There was no significant change in LPP amplitude due to the tDCS application.

Conclusions: These findings validate that tDCS mitigates initial attentional bias, but not the sustained motivated attention, to MA stimuli. Importantly, however, results also show that the individual differences in the effects of tDCS may be underpinned by communication efficiency of the BCN topology, and therefore, these BCN topology metrics may have the potential to robustly predict the effectiveness of tDCS-based interventions on MA craving and attentional bias to MA stimuli among IMUD.