PRIMATE STRIATONIGRAL PROJECTIONS - A COMPARISON OF THE SENSORIMOTOR-RELATED STRIATUM AND THE VENTRAL STRIATUM

The striatum receives topographic cortical inputs with the limbic lobe terminating in the ventral striatum and sensorimotor cortical regions terminating in the dorsolateral striatum. The organization of striato nigral projections originating from these different striatal territori es was examined in primate by using several anterograde tracers. The v entral striatum innervates a large area of the substantia nigra, inclu ding the medial pars reticulata and much of the pars compacta. Moreove r, projections from separate areas of the ventral striatum overlap con siderably in the substantia nigra. No mediolateral or rostrocaudal top ographic order is apparent, and the area of the substantia nigra assoc iated with the ventral striatum is extensive. In contrast, the sensori motor-related striatum innervates a limited region of the ventrolatera l substantia nigra. Similar to ventral striatonigral projections, proj ections originating from different areas of the sensorimotor-related s triatum send converging inputs to the substantia nigra. Sensorimotor-r elated striatonigral projections avoid the region of the dopaminergic neurons in the dorsal pars compacta. Striatonigral projections from th e sensorimotor-related and ventral striatum do not overlap in the subs tantia nigra. Examination of the outputs of discrete striatal loci ind icates that the organization of striatonigral projections is more rela ted to corticostriatal inputs than to a simple rostrocaudal, dorsovent ral, or mediolateral topography of the striatum. Striatal projections that originate from different striatal territories are distinct and no noverlapping, thus supporting the concept of segregated striatonigral circuits. However, areas of the striatum that receive common cortical inputs send converging inputs to the substantia nigra. This suggests t hat the substantia nigra is also an important link for integrating inf ormation between functionally related (sub)circuits. (C) 1994 Wiley-Li ss, Inc.