TMS and tDCS as potential tools for the treatment of cognitive deficits in Parkinson's disease: a meta-analysis.

Background: Cognitive deficits are common nonmotor symptoms in Parkinson's disease (PD). Non-Invasive Brain Stimulation (NIBS) could be a potential aid to prevent or delay dementia progression in this clinical population. However, previous studies reported controversial results concerning their efficacy on cognitive symptoms of PD.