Talk:Corticospinal tract
From Wikipedia, the free encyclopedia
What is the evolutionary advantage of the pyramidal decussation? Anyone? -- FirstPrinciples
- Why not put the question on the Reference desk, where everyone can see it? :-) --Ardonik 10:02, Jul 19, 2004 (UTC)
[edit] Evolutionary advantage of the pyramidal decussation
(Archived from the Reference Desk)
What is the evolutionary advantage of the pyramidal decussation - indeed, neuronal decussations in general (e.g. the optic chiasm)? What pressures would cause such a system to evolve? (To me, the entire 'split-brain' system seems to be prima facie inefficient.) Can anyone enlighten me? -- FirstPrinciples 15:28, Aug 15, 2004 (UTC)
- Your question suggests that you believe efficiency is a hallmark of evolution, which of course it is not! Systems evolve by a variety of fortuitous outcomes, false starts, and contingent events, and in response to changing environments: efficiency would imply design, not evolution. - Nunh-huh 05:42, 16 Aug 2004 (UTC)
- Very simple answer. The split brain allows specialization of the hemispheres rather than simple duplication. The advantage of a "spare brain" (like a spare kidney) is less than the advantage of "2 brains" that to some extent do different things. (And yes, a complete split would be bad, and yes some symmetrical motor functions are retained). Alteripse 16:03, 15 Aug 2004 (UTC)
| Left | Right |
|---|---|
| verbal | visual |
| linguistic | spatial |
| concrete | abstract |
-
- However, it is possible for a person to function with damage to the corpus callosum (with various effects). There is normally considerable intercommunication between hemispheres due to their high degrees of specialization. A split brain allows complex analysis according to opposite (but synergistic) paradigms simultaneously without interference (parallel processing). In this way, a complex result incorporating both paradigms is obtained without loss of efficiency for either. --Eequor 16:41, 15 Aug 2004 (UTC)
- The decussation may be a survival trait. Crossover of motor function may ensure that a damaged part of the body is less likely to be associated with similar damage to the region of the brain controlling it, as they are on opposite sides. --Eequor 16:41, 15 Aug 2004 (UTC)
While we're on the subject, does the Corticospinal tract article describe only the human nervous system, or all mammalian ones, or some other class? It would be nice if there were a statement in that article describing its scope. -- Heron 17:29, 15 Aug 2004 (UTC)
- I'm pretty sure the Corticospinal tract article refers only to the human nervous system. In other animals, even other primates, the basic layout of the brain can be significantly different. (Side note: in my experience there are several articles out there about general anatomy that are implicitly about human anatomy. The penis wiki comes to mind, which deals with the human penis as if it is "the" exemplar of all penises in all species. We should be careful to avoid the trap of anthropocentrism.) -- FirstPrinciples 01:53, 16 Aug 2004 (UTC) -- not to mention phallocentrism! -- Alteripse 01:57, 16 Aug 2004 (UTC)
It (probably) does refer to the human spinal cord in particular. In monkeys and cats, for example, messages for fine distal muscle movements are carried by the rubrospinal tract - rather than the phylogenetically younger corticospinal tract. Chris.
[edit] Mistake!!!
The pyramidal tract is a big collection of tracts and the corticospinal tract is a part of the pyramidal tract, with the corticobulbar (corticonuclear) tract and corticomesencephalic tract. This is a major mistake and needs to be corrected! Its a general misundertsanding since the major part of the pyramidal tract is the corticospinal tract (therefore often used as a general term).
I do not feel that I can correct this in tire article since Im only a medical student in process of learning about the body and its neural system.
