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
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