Endogenous Action Selection Processes in Dorsolateral Prefrontal Cortex Contribute to Sense of Agency: A Meta-Analysis of tDCS Studies of 'Intentional Binding'

Background: Sense of agency is the experience of being in control of one's own actions and their consequences. The role of frontal cortex in this aspect of action control and awareness remains unclear. Objective/hypothesis: Given the role of dorsolateral prefrontal cortex (DLPFC) in action selection, we predicted that DLPFC may contribute to sense of agency when participants select between multiple actions. Methods: We performed a series of experiments by manipulating a range of task parameters related to action selection and action outcomes while participants were exposed to tDCS stimulation of the left DLPFC. We measured the temporal association between a voluntary action and its outcome using the intentional binding effect, as an implicit measure of sense of agency. Results: Fixed-effect meta-analysis of our primary data showed a trend towards a frontal tDCS, together with considerable heterogeneity between our experiments. Classifying the experiments into subsets of studies, according to whether participants endogenously selected between alternative actions or not, explained 71% of this heterogeneity. Anodal stimulation of DLPFC increased the temporal binding of actions towards tones in the subset of studies involving endogenous action selection, but not in the other studies. Conclusions: DLPFC may contribute to sense of agency when participants selected between multiple actions. This enhanced feeling of control over voluntary actions could be related to the observed therapeutic effects of frontal tDCS in depression. (C) 2016 The Authors. Published by Elsevier Inc.