Wednesday, 3 June 2009

4. Introductory concepts: brain forms - A.


Homology. The general idea is shown on the left. An item of content in an organic form (like the thumb of a flying fox) is the homologue of an item of content in another organic form (like the thumb of a human) if some significant content-to-form relation is the same in both and both forms derive from a common ancestor.

In brain biology, this may be extended to further levels of analysis. For example, as shown on the right, items of content in bacteria like the molecular Sensors, Transmitters, Receivers and Motor units (S, T, R, M) are legitimately seen as the 'long-distance' or 'deep' molecular homologues of the neural versions in humans. [Modern bacteria and modern humans derive from a common (bacterial) ancestor. ]

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