Fig. 12. Schematic of the major connections of core and shell, showing a remarkable degree of similarity in the overall patterns of connectivity within the projections to and from lMANcore and lMANshell. In addition to the DLMDL→lMANcore→RA and DLMVM→lMANshell→Ad projections, which parallel each other (Johnson et al., 1995), the lMANcore→Area X circuit (Vates and Nottebohm, 1995) mirrors the lMANshell→LPO circuit (present study). Both Area X and LPO project to the thalamic nucleus DLM (Bottjer et al., 1989; S. Iyengar and S. W. Bottjer, unpublished observations), forming loops that may provide feedback about song to the rest of the song control circuitry. The RA/Ad→DLM→lMAN loops (Wild, 1993b; Brady, Cribbs, and Bottjer, unpublished observations) may be important for integrating descending motor output (RA) and diverse kinds of sensory information (Ad, see below) with song learning. Both Area X and RA of the core pathway receive afferent input from the higher vocal center (HVC) (Nottebohm et al., 1976), which is paralleled by analogous projections from dNCL onto LPO and Ad within the shell pathway (Brady, Cribbs, and Bottjer, unpublished observations). Additionally, the mMAN→HVC circuit within the core projection (Nottebohm et al., 1982; Foster et al., 1997;Foster and Bottjer, 1998) is mirrored by the lMANshell→dNCL circuit (present study) within the shell pathway. Interestingly, the Ad→SN/AVT circuit (Brady, Cribbs, and Bottjer, unpublished observations), which provides dopaminergic input to Area X and LPO (Lewis et al., 1981), may influence both core and shell pathways. Links between these two pathways are also provided by the RA/Ad→DLM/DMP→lMAN/mMAN projections (Foster et al., 1997) (data not shown), through efferent targets of mMAN, that is, HVC and Area X.LPO, Parolfactory lobe, the medial component of the avian striatum; HVC, higher vocal center;mMAN, medial magnocellular nucleus of the anterior neostriatum; dNCL, caudolateral neostriatum;DMP, dorsomedial nucleus of the posterior thalamus.