Cerebellum-like structures

This was news to me, but maybe not to everyone. Everyone’s all impressed with the regularity of cerebellar wiring. Well, how much neater it is when you hear that that architecture may not be just in the cerebellum; in various species, there are a handful of structures similar to cerebellums. And they may have similar functions.

These are separate structures found in species which also have cerebellums (all vertebrates have cerebellums, by the way). At this point, it is debatable how “similar” they really are, but they tend to have:

  • analogs to granule cells
  • analogs to Purkinje cells
    • with spiny apical dendrites and also either basilar dendrites or smooth proximal regions of the apical dendrites
  • sensory input to the Purkinje-like cells organized in a topographic map. The afferents synapse onto the basilar dendrites or the proximal parts of the apical dendrites.
  • parallel fibers going from the granule cells to the Purkinje cells, each one contacting many Purkinje cells in many parts of the topographic map.
  • embryological origins in the alar or sensory plate

Some of them have also been shown in in vivo experiments to have electrophysiological responses which learn in ways similar to the way the cerebellum does in classical conditioning (think rabbit eye puff experiment).

A notable difference between these structures and the cerebellum is that they don’t have climbing fibers.

Curtis Bell (below) theorizes that all of these structures’ function is to filter expected patterns out of incoming sensory signals.

Quoting/paraphrasing from the paper below, the structures are:

  • medial octavolateral nucleus (MON) (in most basal aquatic vertebrates and in some myxinoids)
  • dorsal octavolateral nucleus (DON) (in most of the same basal aquatic vertebrates as the MON, except for the bony fish (neopterygii), where it is entirely absent)
  • marginal layer of the optic tectum (in all ray finned fish (actinopterygii)
  • electro-sensory lobe (ELL) (in a few groups of advanced bony fish (teleosteii))
  • the rostrolateral nucleus (RLN) of the thalamus (in a few groups of bony fish)
  • dorsal cochlear nucleus (DCN) (in almost all mammals)

For more about this, check out this paper:

Curtis C. Bell. Evolution of Cerebellum-Like Structures. Brain, Behavior and Evolution 2002;59:312-326 (DOI: 10.1159/000063567)

See also:

Anna Devor. Is the cerebellum like cerebellar-like structures?. Brain Research Reviews, Volume 34, Issue 3, December 2000, Pages 149-156.

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