Crossed nervous system?

Mark Mattson mpm at seqanal.mi.uky.edu
Mon Jul 11 14:18:16 EST 1994

scott at PSYCH.TORONTO.EDU wrote:

: I think this would be the place to ask such a question, so here it is.

: What are the current theories as to why the nervous system is mostly crossed?
: What are the benefits which are thought to be gained from such a setup?

: A novice wants to know.  :-)

: scott at psych.toronto.edu       | "They are in you and in me; they created us,
: Brian Scott                   |  body & mind; and their preservation is the
: Department of Psychology      |  ultimate rationale for our existence."
: University of Toronto, Canada |         - Richard Dawkins (The Selfish Gene)

I have never read any evolutionary arguments on this topic, but I always
assumed that this occured very early in evolution as a mechanism to allow
self-defense against a directional threat, e.g. fighting a predator on the 
left after it had damaged the left side of the head.  

I know this is weak, but it's the first thing that popped into my head when
I first learned of this crossing phenomenon as a student.

Steven W. Barger, Ph.D.
Sanders-Brown Center on Aging

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