Description of the PD patient's group (N = 12).

Mean ± SD and variance range is reported for each parameter. MMSE – Mini Mental State Examination. The UPDRS-III was assessed in OFF condition (medication OFF in session 1; medication OFF and STN DBS OFF in sessions 2 and 3) and in mON condition (after administration of 250 mg of levodopa/carbidopa) in session 1 and in sON condition (medication OFF and bilateral STN DBS ON) in sessions 2, 3, 4. DBS parameters – mean amplitude, variance in pulse duration, frequency and mode of stimulation in both hemispheres. Medtronic electrode (type 3389) positions were measured in native space according to methodology [37] on T1-MRI obtained one year after surgery: The x-coordinate of each contact 0 and 3 was measured from the wall of the third ventricle (+ towards right; − towards left), whereas the y-coordinate (+ towards anterior; − towards posterior) and z-coordinate (+ towards vertex; − towards brainstem) were measured from the mid-commissural point.