Approach Motivation and Reward Sensitivity: Effects of High‐Definition Transcranial Direct Current Stimulation (HD‐tDCS) to Brain Hemispheres on Effort‐Related Cardiovascular Response

Comprehensive Summary

This study looks at how brain hemisphere stimulation impacts effort intensity. High-definition transcranial direct current stimulation was applied to the dorsolateral prefrontal cortex to directly influence activity in the left or right hemisphere and examine how this would affect cardiovascular responses. 102 student participants from different departments at the University of Geneva were recruited. Each participant was randomly assigned to an experimental condition- right cathodal, left cathodal, or sham stimulation. Five participants were excluded from the main analysis after a check of signal quality and potential outliers. A Cardioscreen 1000 system was used to measure the pre-ejection period and heart rate from ECG and ICG signals. Electrodes were placed on the left and right sides of the participants’ necks and chests, and the signals from these electrodes were amplified, digitized, and analyzed. The Bayesian statistical analysis showed that participants, and particularly women, showed increased effort when performing tasks after right cathodal stimulation rather than left cathodal stimulation and sham stimulations. Post hoc Bayesian statistical analysis showed that men had higher effort-related responses after left cathodal stimulation than after right cathodal stimulation and sham stimulations. The results indicate that brain stimulation conditions alter the effect of effort intensity on sex.

Outcomes and Implications

The results of this study add to the literature on effort and motivation by showing that altering frontal hemispheric asymmetries with HD-tDCS can alter effort-related cardiovascular responses during mentally taxing concentration tasks. This study could have implications for people with psychiatric disorders that relate to the motivation and reward pathways, like depression. The study shows that changing asymmetry affects how much effort a patient will put into achieving something when they know a reward is present. HD-tDCS could be used as a treatment for patients with low motivation, as they could be given rewards for performing specific tasks. Physicians can also use PEP reactivity as a marker of how a patient’s motivation pathway is functioning and how well they respond to various therapies.