Comparative Anatomy
Early neurophysiologists suggest that retinal and inertial signals were selected for about 450 million years ago by primitive brainstem-cerebellar circuitry because of their relationship with the environment. Microscopically, it is evident that Purkinje cell precursors arose from granule cells, first forming in irregular patterns, then progressively becoming organized in a layered fashion. Evolutionarily, the Purkinje cells then developed extensive dendritic trees that increasingly became confined to a single plane, through which the axons of granule cells threaded, eventually forming a neuronal grid of right angles. The origin of the cerebellum is in close association with that of the nuclei of the vestibular cranial nerve and lateral line nerves, perhaps suggesting that this part of the cerebellum originated as a means of carrying out transformations of the coordinate system from input data of the vestibular organ and the lateral line organs. This suggests that the function of the cerebellum evolved as a mode of computing and representing an image relating to the position of the body in space. The cerebellar vermis evolved in conjunction with the hemispheres; this is seen in lampreys and higher vertebrates.
Read more about this topic: Cerebellar Vermis
Famous quotes containing the words comparative and/or anatomy:
“The utmost familiarity with dead streams, or with the ocean, would not prepare a man for this peculiar navigation; and the most skillful boatman anywhere else would here be obliged to take out his boat and carry round a hundred times, still with great risk, as well as delay, where the practiced batteau-man poles up with comparative ease and safety.”
—Henry David Thoreau (1817–1862)
“But a man must keep an eye on his servants, if he would not have them rule him. Man is a shrewd inventor, and is ever taking the hint of a new machine from his own structure, adapting some secret of his own anatomy in iron, wood, and leather, to some required function in the work of the world. But it is found that the machine unmans the user. What he gains in making cloth, he loses in general power.”
—Ralph Waldo Emerson (1803–1882)