Auditory-vocal cholinergic pathway in zebra finch brain.

THE two main song control nuclei in the zebra finch forebrain, the higher vocal center (HVC) and the robust nucleus of the archistriatum (RA), receive cholinergic innervation from the ventral paleostriatum (VP) of the basal forebrain which may play a key role in song learning. By injecting two kinds of neuroanatomical tracers, we found that a topographically segregated pathway from nucleus ovoidalis (Ov) and nucleus dorsomedialis posterior thalami (DMP) to VP and further to RA and HVC. Ov is known as a major relay in the main ascending auditory pathway. The results suggest that cholinergic neurons in the VP which are responsible for song learning are regulated by auditory information from the Ov.