Prosencephalic pathways related to the paleostriatum of the pigeon ( Columba livia)

Abstract

Afferent connections of the avian paleostriatal complex were traced by means of anterograde and retrograde transport of horseradish peroxidase (HRP). The paleostriatum augmentatum (PA), a cell field comparable to mammalian caudate nucleus and putamen, was found to receive projections from a distinct population of telencephalic neurons in the temporal-parietal-occipital (TPO) and lateral cortical (CDL) areas of the neostriatum. TPO neurons, in turn, were found to receive projections from the contralateral ventral archistriatum (Av) and from neurons in the ipsilateral frontal neostriatum adjacent to the rostal portion of the ectostriatum (E). The paleostriatum primitivum (PP), comparable to globus pallidus, receives projections from the small cells of PA, and from neurons in the anterior nucleus of the ansa lenticularis (ALa). ALa appears similar to the mammalian subthalamic nucleus of the basis of its afferent and efferent connections. In addition, PA was also found to receive extensive projections from the nucleus tegmenti pedunculopontinus of the midbrain, a dopamine-containing cell group. Evidence of projections from the nucleus dorsointermedius posterior (DIP), a cell group receiving both cerebellar and paleostriatal afferents, to the rostral telencephalon was also found.