The purpose of this study is to investigate the safety and tolerability of JNJ-61393215 versus placebo after single oral dose administration under fasted (ascending dose levels) and fed condition, to characterize the pharmacokinetics of JNJ-61393125 in plasma, cerebrospinal fluid (CSF) and urine after single oral dose administration and to investigate the effect of food (high fat/high calorie) on the pharmacokinetics of JNJ-61393215 following single oral dose administration.

Inclusion Criteria:

• Participants must have a body mass index (BMI) between 18 and 30 kilogram per meter square kg/m^2, inclusive (BMI = weight/height^2)
• Participant must be healthy on the basis of physical examination, medical history, vital signs, and 12-lead electrocardiogram (ECG) performed at Screening and admission to the clinical unit. Minor abnormalities in ECG, which are not considered to be of clinical significance by the investigator, are acceptable. The presence of Left Bundle Branch Block (LBBB), Atrioventricular (AV) Block (second degree or higher), or a permanent pacemaker or implantable cardioverter defibrillator [ICD] will lead to exclusion
• Participants must be healthy on the basis of clinical laboratory tests performed at screening. If the results of the serum chemistry panel, hematology or urinalysis are outside the normal reference ranges, the subject may be included only if the investigator judges the abnormalities to be not clinically significant
• A man who is sexually active with a woman of childbearing potential and has not had a vasectomy must agree to use a barrier method of birth control example, either condom with spermicidal foam/gel/film/cream/suppository or partner with occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam/gel/film/cream/suppository during the study and for 3 months after receiving the last dose of study drug. All men must also not donate sperm during the study and for 3 months after receiving the last dose of study drug. In addition, their female partner should also use an appropriate method of birth control for at least the same duration.
• Healthy male participants between 18 and 54 years of age, inclusive for Part 1 and 3
• Healthy male and female participants between 55 and 75 years of age, inclusive in Part 2

Exclusion Criteria:

• Participant has a history of or current liver or renal insufficiency; significant cardiac, vascular, pulmonary, gastrointestinal, endocrine, neurologic, hematologic (including coagulation disorders), rheumatologic, psychiatric, or metabolic disturbances, any inflammatory illness or any other illness. Minor deviations, which are not considered to be of clinical significance to both the investigator and to the Janssen Safety Responsible Physician, are acceptable
• Participant has estimated glomerular filtration rate (eGFR) less than (<) 60 milliliters per minute per 1.73 meter square (mL/min/1.73m^2) at Screening
• Participant has a heart rate less than (<) 50 beats per minute (bpm) at Screening or at admission to the clinical unit
• Participant has a history of hepatitis B surface antigen (HBsAg) or hepatitis C antibody (anti-HCV) positive, or other clinically active liver disease, or tests positive for HBsAg or anti-HCV at Screening
• Participant has Left Bundle Branch Block (LBBB), Atrioventricular (AV) Block (second degree or higher), or a permanent pacemaker or implantable cardioverter defibrillator [ICD]