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

## TL;DR

This study shows that stimulating different sides of the brain affects how hard people work, with different effects in men and women.

## Contribution

The study reveals sex-specific effects of HD-tDCS on effort-related cardiovascular responses during mental tasks.

## Key findings

- Right cathodal stimulation increased PEP and SBP reactivity, indicating higher effort in women.
- Men showed contrasting cardiovascular responses to brain stimulation compared to women.
- The effect was not observed in sham or left cathodal stimulation conditions.

## Abstract

This study examined the effect of brain hemisphere stimulation on effort intensity. We applied high‐definition transcranial direct current stimulation (HD‐tDCS) to the dorsolateral prefrontal cortex (dlPFC) to manipulate left or right hemispheric activity and assess its impact on cardiovascular responses reflecting effort. In total, 102 participants (65 women, 37 men) performed a mental concentration task under right cathodal, left cathodal, or sham stimulation conditions. We recorded cardiovascular responses, including pre‐ejection period (PEP), systolic blood pressure (SBP), heart rate (HR), and diastolic blood pressure (DBP). Preregistered hypotheses predicted right cathodal stimulation to lead to greater left frontal hemispheric activity. This should result in higher effort during a mental concentration task of unclear difficulty by increasing approach motivation and thus success importance. As predicted, right cathodal stimulation increased PEP and SBP reactivity, indicating higher effort compared to the left cathodal and sham stimulation conditions. However, this effect was only evident in women, with men exhibiting a contrasting pattern. Our findings highlight the sex‐specific effects of brain stimulation on cardiovascular responses reflecting effort, with the anticipated effects appearing in women.

Brain stimulation over the dorsolateral prefrontal cortex affects effort‐related cardiovascular responses during a mental concentration task of unclear difficulty in presence of moderate incentives. Right cathodal stimulation leads to higher physiological effort compared to left cathodal and sham stimulation. This effect is particularly pronounced in women, whereas men exhibit a contrasting response.