ABSTRACT
The efferent and afferent projections of the hyperstriatum ventrale, pars caudal nucleus (HVc) in carduelis spinus were investigated using anterograde and retrograde HRP tracing techniques. After injecting HRP into the HVc, anterogradely labelled fibers and terminals were observed in the robust nucleus of the archistriatum (RA), tractus archistriatum dorsalis (DA) and the area X of lobus parolfactorius. The dense retrogradely labelled cell bodies were found in medial magnocellular nucleus of the anterior neostriatum (mMAN), nucleus interfacialis (NIf) of midneostriatum, telencephalic auditory area--field L of the neostriatum, and locus ceruleus (LoC) of pons. All these projections were ipsilateral. Based on the present and previous studies, the authors got the following understanding: 1. The HVc projects to the high vocal control centre--RA. This proved that the HVc is also a high vocal control nucleus. 2. The HVc receives afferent projections from the telencephalic auditory area--field L. It indicates that there are direct connection between the two high centres of audition and vocal control nuclei in telencephalon. 3. This study demonstrated that the HVc receives afferent projection from the LoC for the first time. According to the fact, we presume that HVc may be involved in the neural regulations of vegetative function and emotional reactions. 4. The HVc also receives afferent projections from the mMAN and NIf of neostriatum, and from the Uva of the thalamus. On the other hand the HVc projects to area X. Since the mMAN, NIf, Uva and area X are vocal learning and memory centres, therefore the HVc may be also involve in vocal learning and memory functions.