Spatial organization of amygdaloid, nigral, and tegmental projections in the dog neostriatum.

Axonal transport of retrograde markers was used to study the distribution of projections from functionally diverse subcortical structures (the substantia nigra, the ventral tegmental area, and the amygdaloid body) in the caudate nucleus and putamen of the dog. Striatal structures were found to contain regions receiving projections from limbic structures or formations involved largely in motor acts. These structures also contained regions with concordant terminal fields from neurons of these and other functional structures. These results provide a morphological basis for interactions of information currents of different functional significance in the striatum, as well as providing a foundation for their functional heterogeneity. These allow a deeper understanding of their roles in the systems organization of behavior and integrative brain activity.