Non-invasive Brain Stimulation for the Treatment of Mild Cognitive Impairment in Parkinson's Disease

Inclusion Criteria: * Clinical diagnosis of Parkinson's disease, diagnosed by a neurologist; * Mild to moderate disease stage (Hoehn \& Yahr disease stage \< 4); * Movement Disorders Society level I criteria for PD-MCI (Litvan et al., 2012): * Montreal Cognitive Assessment score range \[21-25\] (Dalrymple-Alford et al., 2010), or * performance 1-2 SD below appropriate norms on at least 2 neuropsychological tests, or * classification of PD-MCI based on recent (\< 6 months previous to participation) neuropsychological assessment taken elsewhere (report will be requested);- In case of (dopaminergic) medication use, participants are on stable medication for at least one month before participation and expect to remain on stable medication during the study Exclusion Criteria: * Indication for dementia based on the SAGE (cut-off ≤ 14; Scharre et al., 2010); * Severe depressive disorder (Beck Depression Inventory - Ib score \> 18); * Psychotic disorder (except for benign hallucinations with insight), screened with the Scale for Assessment of Positive Symptoms for Parkinson's disease; * Indication of alcohol or drug abuse; * Contra-indication for rTMS according to Magstim Rapid2 Manual; rTMS should not be: * used on or in the vicinity of patients or users with cardiac demand pacemakers, implanted medication pumps, cochlear devices, implanted defibrillators and/or implanted neurostimulators * used on or in the vicinity of patients with implanted metal objects• used on patients where the skin in the area to be contacted is broken * used on those with large ischaemic scars * used on pregnant women * used on infants under the age of 2 years * used on epileptic individuals * used on those with a family history of convulsions * used on individuals with brain lesions that could affect seizure threshold * used on individuals suffering from multiple sclerosis * used on individuals taking tricyclic antidepressants, neuroleptic agents or any other drug that could lower seizure threshold, * used on individuals suffering from sleep deprivation during rTMS procedures * used on individuals with a heavy consumption of alcohol or those using epileptogenic drugs * used on individuals with severe heart disease or with increased intracranial pressure be used on those who have uncontrolled migraines * Contra-indication for tDCS according to Neuroelectrics Starstim Manual; tDCS should not be used in case of: * Patients with a history of seizures; * Patients with unexplained episodes of loss of consciousness, since such condition could be related with brain alterations or epilepsy; * Patients with unstable or non-controlled neuropsychiatric illness; * Patients having implanted brain medical devices; * Patients with implanted pacemakers; * Patients having any electrically, magnetically or mechanically activated implant; * Patients having cardiac, neural or medication implants; * Patients having vascular clips or any other electrically sensitive support system in the brain; * Patients with serious brain injury; * Patients showing damage of skin at sites of stimulation (the device can only be used in healthy skin without wounds, otherwise the resistance to current can be altered); * Patients suffering from skin problems, such as dermatitis, psoriasis or eczema; * Patients suffering from severe or frequent headaches; * Patients with any serious life-threatening disease such as congestive heart failure, pulmonary obstructive chronic disease or active neoplasia; * Pregnant women (women of childbearing age should undertake a pregnancy test to confirm eligibility before treatment). * Contra-indication for MR imaging: * metal in the body (pacemaker, port-a-cath, prosthesis, (cochlear) implant) * previous brain surgery * head trauma that resulted in unconsciousness for at least 1 hour * clips * (old metal containing) tattoo * irremovable piercings * irremovable metal braces * pregnancy * claustrophobia other problems lying still for 45 minutes * metal in the teeth * neurostimulator (including deep brain stimulation) * Space-occupying lesion on MRI.