diseases is given by pahapill and lozano (2000). it plays an important role in awakeness and sleep. it has a dual role as a regulator of, and of being regulated by the basal ganglia. outputs of the basal ganglia system in the cortico-basal ganglia-thalamo-cortical loop the basal ganglia are interconnected, with little output to external targets. one target is the superior colliculus, from the pars reticulata. the two other major output subsystems are to the thalamus and from there to the cortex. in the thalamus the gpimedial fibers are separated from the nigral as their terminal arborisations do not mix. the thalamus relays the nigral output to the premotor and to the frontal cortices. medial pallidum to thalamic vl and from there to cortex the thalamic fasciculus (h1 field) consists of fibers from the ansa lenticularis and from the lenticular fasciculus (h2 field), coming from different portions of the gpi. these tracts are collectively the pallidothalamic tracts and join before they enter the ventral anterior nucleus of the thalamus. pallidal axons have their own territory in the ventral lateral nucleus (vl); separated from the cerebellar and nigral territories. the vl is stained for calbindin and acetylcholinesterase. the axons ascend in the nucleus where they branch profusely. the vl output goes preferentially to the supplementary motor cortex (sma), to the presma and to a lesser extent to the motor cortex. the pallidothalamic axons give branches to the pars media of the central complex which sends axons to the premotor and accessory motor cortex. snpr to thalamic va and from there to cortex the ventral anterior nucleus (va) output targets the premotor cortex, the anterior cingulate cortex and the oculomotor cortex, without significant connection to the motor cortex.