Inclusion Criteria:  Willingness to sign an informed consent Body mass index (BMI) between 18.5 and 35 Suffered a stroke at least one year ago; and at the age of 40 or later Objective cognitive complaint: memory performance on the delayed recall in the 15 words VWLT of below the normative score (corrected for education, sex and age)  Exclusion Criteria:  Normal Pressure Hydrocephalus (NPH) Morbus Huntington Parkinson's disease HIV/AIDS Hepatitis C & B Recent Transient Ischemic Attack (TIA) (< 1 years) Cerebrovascular Accident (<1 years) Chronic Obstructive Pulmonary Disease (COPD) type Gold 3 and 4 History of schizophrenia, bipolar disorder or psychotic symptoms not otherwise specified or previous treatment for these diseases (lifetime) Risk of suicidal behaviour Current affective disorder (i.e. anxiety or major depression) Cognitive problems due to alcohol abuse, brain tumor, epilepsy, encephalitis or lack of capacity to consent to participation. Current treatment with (or illicit use of) cannabis, opiates, benzodiazepines, MDMA and cocaine Patients with moderate or major liver impairments will be excluded (e.g. Child-Pugh B and C). Use of medication showing strong inhibition of either CYP3A4 or CYP1A2 Patients with rare hereditary problems of galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption Patients participating in other drug studies