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. [ http://openisbn.com/search.php?q=0838580343&isbn=1/ GOC:cls GOC:dgh http://purl.obolibrary.org/obo/go/references/0000021 GOC:dph GOC:jid ]