Healthy ageing and pathological ageing in the context of a neurodegenerative disease are both associated with changes in brain network integrity. Episodic memory is especially affected in Alzheimer's disease, but is also decreased in healthy ageing. Consequently, the memory-relevant brain networks are especially altered. Transcranial direct current stimulation (tDCS) has previously been implemented in different clinical- and non-clinical settings and has shown to beneficially influence network connectivity. The neural correlates of single-session tDCS have been investigated, however, the neural effects of repeated tDCS remain unknown. Furthermore, knowledge about the (long-term) neural mechanisms of repeated tDCS can give valuable insights and possibly pave the ground for exploring tDCS as a treatment option in future studies.

Inclusion Criteria:

Patients

• Diagnosis of MCI based on the latest research criteria (clinical assessment at the memory clinic (prof. Frans RJ Verhey): presence of at least a memory impairment, memory complaints expressed by the patient or informant, no problems in daily life functioning, no dementia and presence of biomarkers (Albert et al., 2011)
• Clinical Dementia Rating score of 0.5 (CDR distinguishes a stage of questionable dementia (CDR 0.5) from people termed healthy (CDR 0) and those with mild dementia (CDR 1)
• Mini-Mental State Examination (MMSE) 23 and being mentally competent (in general, individuals with a MMSE 18 are considered mentally competent)
• Age: between 60 and 85 years old
• 50% female
• Right-handedness
• Average level of education (CBS level 3-4-5-6)

Healthy controls

• Average neuropsychological test results, in accordance with normative data, corrected for age, education and gender
• No substantial memory complaints (according to the participant)
• Age: between 60 and 85 years old
• 50% female
• Right-handedness
• Average level of education (CBS level 3-4-5-6)
• Normal or corrected to normal vision

Exclusion Criteria:

• Psychoactive medication use
• Abuse of alcohol and drugs
• Cognitive impairment due to alcohol/drug abuse or abuse of other substances
• Past or present psychiatric or neurological disorders (major depression, schizophrenia, bipolar disorder, psychotic disorder (or treatment for it), epilepsy, stroke, Parkinson's disease, multiple sclerosis, brain surgery, brain trauma, electroshock therapy, kidney dialysis, Menière's disease, brain infections)
• Major vascular disorders (e.g. stroke)
• Heart diseases or pacemakers
• Contraindications for scanning (e.g. brain surgery, cardiac pacemaker, metal implants, claustrophobia, body tattoos)
• Large scars or fresh wounds on the scalp