Non-invasive brain stimulation for 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.