A new brain stem pathway for vocal control in the zebra finch song system.

Projections from the telecephalic vocal control nucleus robustus archistriatalis (RA) to the brain stem were studied with anterograde and retrograde tracers in adult male Zebra finches. A previously undescribed projection to the ventrolateral medulla that originates in a dorsal subregion of the RA was found, in addition to the known projections to the tracheosyringeal portion of the hypoglossal nucleus (nXIIts) and to the dorsomedial nucleus of the intercollicular complex (DM), a mesencephalic vocal area. The DM was also found to project to the same area of the lateral medulla, which in turn projects to the nXIIts. This area in the lateral medulla includes the nucleus ambiguus, and may be of a pathway that links the telencephalic vocal pathway with respiratory control areas.