The expression of a7 GFP also persists into the adult animal. This is apparent in the ascending central auditory system nuclei and their fibers (Fig. 7C) . After the cochlear nucleus, a7 GFP is present in the ventral lateral lemniscus, on through the dorsal lateral lemniscus, and to the inferior colliculus where dense staining of a7 GFP is present ( Fig. 7C ; Morley and Happe 2000; Yao and Godfrey 1999) . The commissural fibers of the inferior colliculus are also identified by a7 GFP expression (Fig. 7D) . Thereafter, efferents follow the brachium of the inferior colliculus to the medial geniculate nucleus where scattered cells expressing a7 GFP were seen. Not shown is that the expression of a7 GFP in the adult auditory cortex appears restricted to cells of layer 1. Labeling of olivocochlear fibers was not detected.