The visual-oculomotor striatum of the cat: functional relationship to the superior colliculus

The visual-recipient sector of the cat striatum receives corticostriate inp ut from over 15 higher visual and oculomotor-related areas of the cortex an d appears homologous with the physiologically characterized region of mixed visual and oculomotor inputs within the primate caudate nucleus. This area in the cat involves the dorsolateral caudate and a strip of the caudal put amen. In a first series of experiments, the former was injected with a retr ograde tracer in several cats. Thalamostriate cells were found in extensive regions, including the intralaminar nuclei, certain motor-related nuclei, and, most notably, across much of the extrageniculate visual thalamus. In a nother set of experiments, anterograde tracers were also injected into the superior colliculus (SC), and labeled tectothalamic fibers were observed in all thalamic sites projecting to the visual-recipient striatum. These find ings highlight for the first time the need for the SC to be considered in m odels of thalamostriate and visual/oculomotor-striatal function(s). Moreove r, the data bring to light the fact that basal-ganglia outflow reaching the SC via striatonigro-nigrotectal circuitry is well positioned to modulate a sc ending tecto-thalamic-thalamostriatal signals destined for the visual-re cipient striatum.