The functional anatomy of the basal ganglia of birds.

To study how the basal ganglia can control movement in birds, we have reinvestigated the connections of the pigeon dorsal pallidum. Our results indicate that avian basal ganglia appear to control movement through major projections to several premotor pretectal and tegmental centres which innervate the tectum, and through a minor projection to a possible motor thalamic centre which innervates the Wulst. For such control, separate striatopallidal output circuits appear to exist in birds that are remarkably similar to those described in mammals, suggesting that avian and mammalian basal ganglia may control movement through similar mechanisms, and that the morphological substrate for such control evolved earlier than previously thought.