The place of the thalamus in frontal cortical-basal ganglia circuits.

The thalamus has long been thought to convey subcortical information to the cortex. Indeed, models of basal ganglia function attribute the primary role for the thalamus to a simple relay of information processed in the basal ganglia to the cortex. The thalamic nuclear groups that are associated primarily with this function are the ventral anterior and ventral lateral nuclei and the mediodorsal thalamic nucleus. However, recent studies have shown that the corticothalamic projection is important for the dynamics of the thalamocortical processing. Furthermore, the relay nuclei that carry basal ganglia output to the cortex have recently been shown to project back to the basal ganglia directly. These two recent developments indicate a more dynamic role for the thalamus in basal ganglia information processing than a passive relay.