Investigation of the Benefits of Electrical Non-invasive Stimulation on Cognitive Symptoms in Parkinson's Disease

interview with a neuropsychologist and carrying out tests measuring overall cognitive abilities, depression, apathy and anxiety (respectively using the MOCA, MADRS, LARS, STAI scales)

Only for patients with Parkinson disease. Evaluation consisting in a disease severity assessment using the Hoehn and Yahr and Schwab and England scales, as a well as a measure of levodopa equivalent daily dose.

"The task consists in pressing a left or right button as fast and as accurately as possible according to the direction of an arrow displayed at the center of a screen. On 25 % of the trials, a stop signal will occur right after the stimulus, indicating the participant to stop his impending button press. The delay between the presentation of the arrow stimulus and the stop signal will be adjusted to ensure a final 50% accuracy (decreased following an accurate response and increased after an error), which is necessary to comply with the assumptions for a robust calculation of the stop signal reaction time (SSRT)."

A high-resolution (256 channels) electroencephalographic recording will be done at rest and during the Stop task, before and after each real or sham stimulation.

Real or sham tACS will be applied with the same equipment (StarStim, Neuroelectrics). The stimulation will consist in applying a current (max 2 mA) at frontal sites (F8 and Cz according to standard EEG position, and defined based on dosimetry analyses on averaged head models) for 12-15 minutes during the task. A 10 s ramp (fade-in/fade-out) will be used to avoid current perception of the stimulation and optimize blinding. Sham stimulation will be done using the same protocol, but with no stimulation in between onset and offset.