Physiological mechanisms associated with non-invasive brain stimulation during gambling-related task performance

Background 

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has been investigated as a tool to improve current treatment approaches for gambling disorder (GD). 

Methods  

In this study, tDCS effects over the autonomous nervous system (ANS) were examined during different reward conditions. Participants consisted of 17 low-risk and high-risk gamblers who were grouped by their self-reported impulsivity levels. Electroencephalogram (EEG), electrodermal activity (EDA) and electrocardiogram (ECG) were measured during gambling-related cognitive task performance while receiving two tDCS sessions (real stimulation and sham). 

Results 

Results revealed tDCS effects over the ANS, associated with an increase of skin conductance level and changes of cortical excitability. Furthermore, the EEG outcomes showed participants intra-individual variability between sessions. Different autonomic arousal was found between groups of low and high impulsive gamblers, and between different reward phases. Specifically, high impulsive gamblers showed higher sympathetic activation (increased EDA and heart rate variability) compared with low impulsive gamblers during wins compared to losses. Lastly, gambling severity correlated positively with cravings, and with EDA and heart rate during cognitive task-performance. 

Conclusion 

Neuromodulation outcomes showed evidence of the capability of tDCS to modulate the ANS, however, due to the lack of effectiveness of blinding during real stimulation, these results should be carefully interpreted. Notably, the correlations between baseline EDA and reward response variables might indicate that EDA could be a potential biomarker to investigate GD. Employing more realistic experimental gambling scenarios in future studies will be essential to improve ecological validity and to better understand problematic gambling behaviour.