A developmental process, independent of morphogenetic (shape) change, that is required for the trochlear nerve to attain its fully functional state. The trochlear nerve is a motor nerve and is the only cranial nerve to exit the brain dorsally. The trochlear nerve innervates the superior oblique muscle. [ GOC:dgh http://purl.obolibrary.org/obo/go/references/0000021 GOC:dph GOC:jid GOC:cls https://www.worldcat.org/search?q=bn%3A0838580343 ]