Two separate areas of the brain differentially guide the development of a song control nucleus in the zebra finch.

A brain nucleus that is important for the generation of song in the adult male zebra finch (Poephila guttata), the robust nucleus of the archistriatum (RA), receives dual inputs from two other telencephalic song nuclei: the hyperstriatum ventrale pars caudale (HVc) and the lateral magnocellular nucleus of the anterior neostriatum (L-MAN). We lesioned each of these afferent inputs to the RA early in development, either by themselves or both at the same time in the same side of the brain, to determine what influences each of these nuclei exerts on the normal development of the RA into adulthood. We found that lesioning the HVc in a 20-day-old male zebra finch prevents the later increase in RA volume and soma size that would normally occur around 35 days post-hatching. MAN lesions at this same early age, on the other hand, had a large effect on reducing the volume and cell number of RA neurons, without affecting soma size. Lesioning both inputs early in development induced considerable RA neuronal cell death and atrophy of the nucleus. This study shows that the development of the RA is affected differently by each of its two input nuclei.