Study Investigating the Effects of JNJ-54861911 on Amyloid-beta Processing in Cerebrospinal Fluid (CSF) and Plasma in Japanese Participants Asymptomatic at Risk for Alzheimer Dementia

This is a multi-center (when more than one hospital or medical school team work on a medical research study), double-blind (neither physician nor participant knows the treatment that the participant receives), placebo-controlled (the experimental treatment or procedure is compared to an inactive substance), randomized (study medication assigned by chance), multiple dose, Proof of Mechanism (POM) study in Japanese participants ARAD. All eligible participants will be randomly assigned to 1 of 3 treatment groups (that is, placebo, JNJ-54861911 10 milligram \[mg\] or JNJ-54861911 50 mg once daily regimen). This study will consist of Screening Phase (8-week), Double blind Treatment Phase (4-week), and Follow-up Phase (2-week). The maximum study duration for a participant will be 14 weeks. Participant's safety will be monitored throughout the study.