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. [ https://www.worldcat.org/search?q=bn%3A0838580343 GOC:cls GOC:jid http://purl.obolibrary.org/obo/go/references/0000021 GOC:dgh GOC:dph ]