Inclusion Criteria:  The participant is ≥18 and ≤45 years of age at the Screening Visit for Cohorts A1 to A6 (excluding cohort A2b) or ≥55 to ≤65 for participants in the CSF sampling Cohorts A2b and A7. The participant has body mass index (BMI) ≥18.5 kilograms (kg)/square meter (m^2) and ≤30 kg/m^2 and body weight ≥60 kilograms (kg) at the Screening Visit and at the Baseline Visit. The participant has a normal resting electroencephalogram (EEG) at Screening. The participant is, in the opinion of the investigator, generally healthy based on medical history, a physical examination, vital signs, an electrocardiogram (ECG), and the results of the clinical chemistry, haematology, urinalysis, serology, and other laboratory tests.  Exclusion Criteria:  The participant has or has had any clinically significant immunological, cardiovascular, respiratory, metabolic, renal, hepatic, gastrointestinal, endocrinological, haematological, dermatological, venereal, neurological, or psychiatric disease or other major disorder.  Other inclusion and exclusion criteria may apply.