Does premotor transcranial direct current stimulation increase motor cortex excitability and improve motor function?

Transcranial direct current stimulation (tDCS) is a non-invasive technique that modulates the excitability of neurons within the primary motor cortex (M1), but might also induce effects in distant brain areas caused by activity of interconnected brain zones (known as functional connectivity). We have previously established protocols for delivery of tDCS, efficacy of tDCS on brain excitability and motor skill performance in healthy individuals. In these experiments, M1 excitability was tested using single-pulse transcranial magnetic stimulation (TMS) before and after 20 minutes of anodal-tDCS application over the left M1. Interestingly, brain excitability increased for both the stimulated and non-stimulated M1 suggesting that the two brain regions are interconnected, denoting the phenemona of functional connectivity. Therefore, the aim of this research is to examine whether premotor (PM) tDCS can modify the excitability of the M1 via cortico-cortical connectivity and its effect on motor function. This study will provide a unique insight into the underlying neural mechanisms contributing to any changes in functional connectivity following tDCS.