Why so much cross-wiring in the brain?

[Perspicuo]

Why does the left side control the right side? Why the decussation of the pyramids?

The mystery pops up once in a while on da webs, and several people have offered different explanations, such as the change from having the spinal cord on the ventral side to one on the dorsal side. That doesn't say much and doesn't seem satisfying. But this next one is much more compelling my view: http://sol.rutgers.edu/~shinbrot/NewHome2006/Papers/Decussation11.pdf

Many vertebrate motor and sensory systems “decussate” or cross the midline to the opposite side of the body. The successful crossing of millions of axons during development requires a complex of tightly controlled regulatory processes. Since these processes have evolved in many distinct systems and organisms, it seems reasonable to presume that decussation confers a significant functional advantage –yet if this is so, the nature of this advantage is not understood. In this article, we examine constraints imposed by topology on the ways that a three dimensional process or and environment can be wired together in a continuous, somatotopic, way. We show that as the number of wiring connections grows, decussated arrangements become overwhelmingly more robust against wiring errors than seemingly simpler same-sided wiring schemes.

Mathematics to the rescue.

 

[fromderinside]

Why does the left side control the right side? Why the decussation of the pyramids?

http://sol.rutgers.edu/~shinbrot/NewHome2006/Papers/Decussation11.pdf

... Since these processes have evolved in many distinct systems and organisms, it seems reasonable to presume that decussation confers a significant functional advantage .... We show that as the number of wiring connections grows, decussated arrangements become overwhelmingly more robust against wiring errors than seemingly simpler same-sided wiring schemes.

Mathematics to the rescue.

Beg to differ. Not so much.

Eyup radially wired organisms, for instance, sometimes tend to pull themselves apart for defensive, conflicting signal, reasons, but, also seem to have retained more regenerative capacity throughout the cellular and system structures. See for instance "Leave it all behind: A taxonomic perspective of autotomy in invertebrates"
http://www.researchgate.net/profile...ertebrates/links/02bfe5100e071a66ac000000.pdf

... and a cephalopod (ocotpus) which is both radial and bifurcated (vision) A View of the Octopus Brain. http://cephalove.blogspot.com/2010/06/view-of-octopus-brain.html

Left and right may not be relevant to such organisms yet here they are competing with the fishes and marine mammals with features available to them (cellular color control, shape change, organ regeneration) not typically available to their bilaterally symmetrical competition.

Seems to me that is that bilateral symmetry necessitates one set of solutions while most of the explanations can be found in just bilaterality and stereoscopic utility are responsible for developing more advanced capacities in modern brains.

Just sayin'.