A developmental process, independent of morphogenetic (shape) change, that is required for the locus ceruleus to attain its fully functional state. The locus ceruleus is a dense cluster of neurons within the dorsorostral pons. This nucleus is the major location of neurons that release norepinephrine throughout the brain, and is responsible for physiological responses to stress and panic. [ GOC:cls http://openisbn.com/search.php?q=0838580343&isbn=1/ GOC:dgh GOC:dph GOC:jid http://purl.obolibrary.org/obo/go/references/0000021 ]