Role of basal ganglia in saccades

The basal ganglia, substantia nigra pars reticulata (SNr) and caudate nucleus, contribute to the suppression and initiation of saccadic eye movements by imposing a tonic inhibition on the superior colliculus (SC) and by removing it. The tonic inhibition originates from the SNr where neurons show continuous, high frequency discharges. With its inhibitory connection to the SNr, the caudate nucleus transiently suppresses the SNr activity thereby removing the tonic inhibition on the SC. Signals carried by neurons in the SNr and the caudate nucleus are both heavily dependent on or selective for different aspects of learned paradigms. Such task-specific, learned information originating from the basal ganglia may open or close the gate for a variety of excitatory inputs to the SC.