# Neurostimulation and Sense of Agency: Three tDCS Experiments on the Modulation of Intentional Binding

## TL;DR

This study explored how tDCS affects the sense of agency by stimulating brain regions like the cerebellum and angular gyrus, but found no significant effects.

## Contribution

The study contributes by systematically testing tDCS effects on sense of agency across multiple brain regions and protocols.

## Key findings

- Offline and online tDCS targeting the cerebellum did not significantly affect sense of agency.
- Inhibitory stimulation of the left angular gyrus also failed to modulate sense of agency.
- The results highlight challenges in replicating previous findings and suggest limitations of tDCS for this purpose.

## Abstract

Objectives: This research investigated the impact of transcranial Direct Current Stimulation (tDCS) on sense of agency (SoA) when focusing on cortical regions like the cerebellum, the dorsolateral prefrontal cortex (DLPFC), and the angular gyrus (AG). To this aim, three experiments were carried out, and agency was assessed through the Wundt Clock Paradigm, which provides a measure of intentional binding. Methods: The first experiment provided offline cathodal stimulation applied to the right cerebellum, with the return electrode placed on the left DLPFC, and participants were randomly assigned to either the placebo group or the active group. The second experiment adopted the same montage as the previous one, but the online stimulation was provided in a within-subjects design. Results: Since none of these studies targeting the cerebellum produced significant results on the agency measures, we carried out a third experiment aimed to replicate a previous study that provided inhibitory stimulation of the left AG. However, this also showed no modulations of SoA. Conclusions: Several explanations could be given for these negative results. For example, the inter-individual variability, task complexity, and limitations of tDCS technology may contribute to the inconsistencies of the results. Also, the failure to replicate a previous study raises the issue of the replicability crisis in psychology. Nevertheless, this study may represent an important reference for research aimed at modulating SoA through the neuromodulation of brain areas included in the agency network. Future studies could benefit from assessing individual cognitive abilities supporting agency, optimizing stimulation protocols, and exploring alternative brain stimulation techniques to obtain significant results.