Is the cerebellum like cerebellar-like structures?

The cerebellum and cerebellar-like structures (including the dorsal and med ial octavolateral nucleus of fishes and amphibians, the electrosensory late ral line lobe of electroreceptive teleost fishes and the dorsal cochlear nu cleus of mammals) have similar anatomy, common developmental origins and co mmon cellular markers. Transplanted embryonic Parkinje cells integrate into cerebellar-like structures but not neighboring brain parenchyma, and mutat ions that cause cerebellar degeneration cause similar defects in cerebellar -like structures. This review advances the idea that these neuroanatomical and molecular similarities have functional equivalents. The main structural difference between the cerebellum and cerebellar-like structures, the infe rior olivary nucleus, can be viewed as a relay station that evolution has i nterposed along the path of flow of primary sensory information to the cere bellum. Gating of sensory information to the cerebellum occurs at the level of inferior olivary nucleus depending on whether arriving information is e xpected. Activation of inferior olivary neurons leads to plasticity, and fi nely tuned inhibitory inputs suppress olivary excitation when the plasticit y is not needed. Functionally, the olive-cerebellar system performs the sam e kind of computation as cerebellar-like structures: the subtraction of sen sory expectations. (C) 2000 Elsevier Science BN. All rights reserved.