 There is controversy, however, regarding the extent to which convergent selective processing occurs versus segregated parallel processing within re-entrant closed loops of the basal ganglia.Regardless, the transformation of the basal ganglia into a cortically re-entrant system in mammalian evolution occurs through a re-direction of pallidal (or "paleostriatum primitivum") output from midbrain targets such as the superior colliculus, as occurs in sauropsid brain, to specific regions of the ventral thalamus and from there back to specified regions of the cerebral cortex that form a subset of those cortical regions projecting into the striatum.The abrupt rostral re-direction of the pathway from the internal segment of the globus pallidus into the ventral thalamus—via the path of the ansa lenticularis—could be viewed as a footprint of this evolutionary transformation of basal ganglia outflow and targeted influence.