Evolutionary Convergence as a Tool in Neuroscience. 13th Annual Karger Workshop, San Diego, Calif., November 9, 2001. Guest Editors: Heather L. Eisthen, East Lansing, Mich., Kiisa C. Nishikawa, Flagstaff, Ariz.

Paper

Evolution of Cerebellum-Like Structures
Curtis C. Bell

Neurological Sciences Institute, Oregon Health and Sciences University, Beaverton, Oreg., USA

Address of Corresponding Author

Brain Behav Evol 2002;59:312-326 (DOI: 10.1159/000063567)

  Key Words

• Cerebellum
• Cerebellum-like structures
• Evolution
• Homology
• Convergence
• Syngeny

  Abstract

All vertebrate brains have a cerebellum, and most of them have one or more additional structures that are histologically similar to the cerebellum. The cerebellum-like structures include the medial octavolateral nucleus in most aquatic vertebrates; the dorsal octavolateral nucleus in many aquatic vertebrates with an electrosensory system; the marginal layer of the optic tectum in ray-finned fishes; electrosensory lobes in the few groups of advanced bony fish with an electrosensory system; the rostrolateral nucleus of the thalamus in a few widely scattered groups of bony fish; and the dorsal cochlear nucleus in all mammals except monotremes. All of these structures receive topographically organized sensory input in their deep layers. Purkinje-like cells receive the sensory input near their cell bodies. These cells extend apical dendrites up into the molecular layer where they receive synaptic input from parallel fibers. The cerebellum itself can be included within this characterization by considering the climbing fiber as at least in part a conveyor of sensory information and by recalling that climbing fibers in more basal vertebrates terminate on smooth dendrites close to the soma. Physiological findings from three different systems suggest the hypothesis that cerebellum-like structures remove predictable features from the sensory inflow. Phylogenetic homology can explain the similarities across different taxa for some types of cerebellum-like structures, but similarities within other types cannot be explained in this way. Moreover, phylogenetic homology cannot explain the similarities among different types of cerebellum-like structures. Evolutionary convergence provides the best explanation for all these similarities that cannot be explained by homology. The convergence is almost surely constrained by the availability of a genetic-developmental program for creating cerebellum-like circuitry and by the need within many different systems for the type of information processing that cerebellum-like circuitry can provide.

Copyright © 2002 S. Karger AG, Basel

  Author Contacts

Curtis C. Bell
Neurological Sciences Institute
Oregon Health and Sciences Institute
505 N.W. 185th Ave., Beaverton, OR 97006 (USA)
Tel. +1 503 418 2575, Fax +1 503 418 2501, E-Mail bellc@ohsu.edu

  Article Information

Number of Print Pages : 15
Number of Figures : 4, Number of Tables : 0, Number of References : 95