HD-tDCS over left supplementary motor area differentially modulated neural correlates of motor planning for speech vs. limb movement.

The supplementary motor area (SMA) is implicated in planning, execution, and control of speech production and limb movement. The SMA is among putative generators of pre-movement EEG activity which is thought to be neural markers of motor planning. In neurological conditions such as Parkinson's disease, abnormal pre-movement neural activity within the SMA has been reported during speech production and limb movement.