Diane
13-04-2008, 09:11 AM
Lately I've been reading Beyond the Zonules of Zinn: A Fantastic Journey Through Your Brain (http://www.amazon.com/Beyond-Zonules-Zinn-Fantastic-Journey/dp/0674026101), by David Bainbridge, which I first heard about from Ginger Campbell's podcast #32. (http://brainsciencpodcast.wordpress.com/2008/03/07/brain-science-podcast-32-a-brief-introduction-to-brain-anatomy/) I started to get fascinated, riveted even, as the author started discussing the deeper evolution and function of the inner organs of the ear. He mentions that the inner ear with all its funny little labyrinths and hair cells is thought to have evolved from the lateral lines of fish. The cells that form these sensitive mechanoreceptors on fish are called neuromasts. The startling thing about hearing, that was news to me from this book, is that most of the cortical neurons that deal with hearing are actually motor.
In humans anything that is signaling that doesn't come straight from neural tube (ectoderm) comes from neural crest (http://www.somasimple.com/forums/showthread.php?p=51452#post51452) (also ectoderm). Plenty of neural crest cell populations end up in the head, including every kind of glia. The sensory nerves for every sense are mostly from neural crest too, if they aren't originally placode (ectoderm too).
For years Nari and I have been talking about the body as that bump on the bottom of the brain, in an effort to drive minds away from the usual PT way of thinking about the brain as the bump up on top of the body. But I never really was as clear about that as I think I have become since dipping into the Zonules book.
An image came to mind (just my own mind, not the book's fault), a schematic of the brain as the hub of a wheel, with senses sticking out from it like spokes, and the body was just another sensorimotor spoke. That's all. The spinal cord just another "nerve" (albeit very large), to and from the brain, both motor and sensory function, conveying info to and fro, just like the optic nerve or the auditory nerve or the trigeminal. Vision takes up a lot more of the brain's attention than the body does, or ever will, something like 40%.
I'm going to think of the spinal nerve as the great big fat Cranial Nerve XIII for awhile. One minor distinction is that it is thought to have preceeded the brain... but that's a small detail for now. Another is that it handles a lot of the processing and is ordinarily considered CNS. But I want to play with the idea of the body as just a large mechanoreceptive motor vehicle for the brain to get itself around, for a little while at least.
In humans anything that is signaling that doesn't come straight from neural tube (ectoderm) comes from neural crest (http://www.somasimple.com/forums/showthread.php?p=51452#post51452) (also ectoderm). Plenty of neural crest cell populations end up in the head, including every kind of glia. The sensory nerves for every sense are mostly from neural crest too, if they aren't originally placode (ectoderm too).
For years Nari and I have been talking about the body as that bump on the bottom of the brain, in an effort to drive minds away from the usual PT way of thinking about the brain as the bump up on top of the body. But I never really was as clear about that as I think I have become since dipping into the Zonules book.
An image came to mind (just my own mind, not the book's fault), a schematic of the brain as the hub of a wheel, with senses sticking out from it like spokes, and the body was just another sensorimotor spoke. That's all. The spinal cord just another "nerve" (albeit very large), to and from the brain, both motor and sensory function, conveying info to and fro, just like the optic nerve or the auditory nerve or the trigeminal. Vision takes up a lot more of the brain's attention than the body does, or ever will, something like 40%.
I'm going to think of the spinal nerve as the great big fat Cranial Nerve XIII for awhile. One minor distinction is that it is thought to have preceeded the brain... but that's a small detail for now. Another is that it handles a lot of the processing and is ordinarily considered CNS. But I want to play with the idea of the body as just a large mechanoreceptive motor vehicle for the brain to get itself around, for a little while at least.