The primary purpose of this study is to investigate the effects of JNJ-54175446 (dose response) on levels of Aβ fragments (Aβ1-42, Aβ1-40, Aβ1-38, Aβ1-37) in plasma and cerebrospinal fluid (CSF), the effects of JNJ-54175446 on markers of (neuro) inflammation/protection in blood and CSF and the pharmacokinetics of JNJ-54175446 followed by single and multiple dose administration.