Comparative Anatomy and Naming
The basal ganglia form one of the basic components of the forebrain, and can be recognized in all species of vertebrates. Even in the lamprey (generally considered one of the most primitive of vertebrates), striatal, pallidal, and nigral elements can be identified on the basis of anatomy and histochemistry.
A clear emergent issue in comparative anatomy of the basal ganglia is the development of this system through phylogeny as a convergent cortically re-entrant loop in conjunction with the development and expansion of the cortical mantle. 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.
Read more about this topic: Basal Ganglia
Famous quotes containing the words comparative, anatomy and/or naming:
“The hill farmer ... always seems to make out somehow with his corn patch, his few vegetables, his rifle, and fishing rod. This self-contained economy creates in the hillman a comparative disinterest in the world’s affairs, along with a disdain of lowland ways. “I don’t go to question the good Lord in his wisdom,” runs the phrasing attributed to a typical mountaineer, “but I jest cain’t see why He put valleys in between the hills.””
—Administration in the State of Arka, U.S. public relief program (1935-1943)
“I love to see, when leaves depart,
The clear anatomy arrive,”
—Roy Campbell (1902–1957)
“Husband,
who am I to reject the naming of foods
in a time of famine?”
—Anne Sexton (1928–1974)