Testing of an Interface for Synchronizing tACS-DBS With a Phase-locked-loop

The investigators aim to test an interface to phase-lock transcranial alternating current stimulation (tACS) and deep brain stimulation (DBS) for future studies investigating the effects of different time-lags between DBS and tACS on the behavioural and neural level. To test if the interface works in patients with DBS, the investigators record EEG during synchronized tACS-DBS in several patients. The investigators hypothesize that they can apply tACS at the desired phase-lags relative to DBS pulses and confirm this with EEG measurements of the DBS and tACS artifact.