The Skeletomotor Cortico-Basal Ganglia-Thalamocortical Circuit

Abstract

According to earlier data, the basal ganglia receives diverse inputs from the entire cerebral cortex and “funneled” these influences via the ventral thalamus to the motor cortex (Allen and Tsukahara 1974; Evarts and Thach 1969; Kemp and Powell 1971). Subsequent studies led to a view that there is segregation of influences from the sensorimotor and association cortices through the basal ganglia-thalamocortical pathway (DeLong and Geor-gopoulos 1981; DeLong et al 1983). Two distinct loops have been distinguished: (1) a “motor” loop passing largely through the putamen that receives inputs from the sensorimotor cortex, and whose influences are transmitted to certain premotor areas, and (2) an “association” (or “complex”) loop passing through the caudate nucleus, that receives input from the association areas, and whose influences are returned to portions of the prefrontal cortex. In recent physiological and anatomical studies, the concept of segregated basal ganglia-thalamocortical pathways has been further developed. The general principle that basal ganglia influences are transmitted only to restricted portions of the frontal lobe has been further reinforced (despite the fact that the striatum receives projections from nearly the entire neocortex).