left-right reversal of CNS: Why?

kenneth paul collins KPCollins at postoffice.worldnet.att.net
Wed Sep 11 21:14:40 EST 1996

>There are not, after all, upper and lower hemispheres to the brain!  
>The left-right reversal actually involves fibers decussating from the 
>left side of the brain to the right side of the body.  There is nothing 
>so clearcut for "upside down".

Well... there is... humans are bipedal... if we're not sitting, or 
sleeping, we are pretty-much always holding our bodies in one special 
orientation with respect to "gravity", etc... our legs just don't 
have ranges of motion that are analogous to the ranges of motion of 
our arms... the inverted visual system is mapped exactly to the inverted 
somatosensory & motor maps in the cortex with respect to this one 
stereotypical body orientation... ken collins

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