Fig. 15.

Our working hypothesis. Area X appears to be a mixture of striatum and globus pallidus. An excitatory response in the HVc may be transmitted to the DLM by two successive inhibitory synapses. Excitation of SNs by glutamatergic HVc input could inhibit the AF cells, briefly reducing their spontaneous activity. This would transiently reduce tonic inhibition in DLM neurons, allowing them to fire. In this manner, the AFP could act as a functional analog of the mammalian direct pathway through the basal ganglia. The projection from LMAN to area X is omitted for the sake of simplicity.VA, Ventral anterior; VL, ventral lateral.