Wednesday, October 12, 2005

Neuromatrix 1: First Contact

I'd read about Melzack’s gate control theory ages ago before picking up Topical Issues in Pain, Volume 3 (edited by Louis Gifford of the UK. published in 2002. available from ). This book is a third in a series dealing with pain and is subtitled, "Sympathetic Nervous System and Pain." Ron Melzack, from McGill University in Canada, worked for decades with Patrick Wall in Britain on uncovering the mysteries of pain.

My interest perked up right away when I read this on page 12, by Ron Melzack, on his updated concept of "neuromatrix":

It is evident that the gate control theory has taken us a long way. Yet, as historians of science have pointed out, good theories are instrumental in producing facts that eventually require a new theory to incorporate them. And this is what has happened. It is possible to make adjustments to the gate theory...But there is a set of observations on pain in paraplegics that just does not fit the theory. This does not negate the gate theory, of course. Peripheral and spinal processes are obviously an important part of pain, and we need to know more about the mechanisms of peripheral inflammation, spinal modulation, midbrain descending control, and so forth. But the data on painful phantoms below the level of total spinal section indicate that we need to go beyond the foramen magnum and into the brain.

My analysis of phantom limb phenomena has led to four conclusions that point toward a new conceptual nervous system.

First, because the phantom limb (or other body part) feels so real, it is reasonable to conclude that the body we normally feel is subserved by the same neural processes in the brain; these brain processs are normally activated and modulated by inputs from the body, but they can act in the absence of any inputs.

Second, all the qualities we normally feel from the body, including pain, are also felt in the absence of inputs from the body; from this we may conclude that the origins of the patterns that underlie the qualities of experience lie in the neural networks in the brain; stimilui may trigger the patterns but do not produce them.

Third, the body is perceived as a unity and is identified as the 'self' distinct from other people and the surrounding world. The experience of a unity of such diverse feelings, including the self as the point of orientation in the surrounding environment, is produced by central neural processes and cannot derive from the peripheral nervous system or spinal cord.

Fourth, the brain processes that underlie the body self are, to an important extent that no longer can be ignored, 'built-in' by genetic specification, although this built-in substrate must, of course, be modified by experience.

After reading Melzack’s perception of what he calls a neuromatrix, I felt my mind do one of those brain avalanches we all get sometimes when a lot of disparate ideas suddenly collapse into each other and begin to make clearer sense. Something called a "body-self neuromatrix" puts out a "neurosignature" that is projected to areas in the brain called "the sentient neural hub"... "in which the stream of nerve impulses (the neurosignature modulated by ongoing inputs) is converted into a continually changing stream of awareness."

Long ago I learned a D.O.’s theory about embryologic connections that don’t fade, regardless of what happens downstream; all the bits that develop together or come from the same "family tree" germ layer will remain in communication, and that pain can spread along this "family tree": Even though the ‘family members’ (embryologic cellular relatives) may be spread far apart in the adult body, they don't ever lose track of each other.

The D.O. theory and the neuromatrix theory didn’t quite collapse into one another successfully, and still haven’t… I hopped over to neuromatrix theory and am still there at present. (However, I look for connections; this blog is an active search for connections. There will be plenty of embryology placed here, therefore.)

As for a "neuromatrix" and a "sentient neural hub" I remember reading (V.S. Ramachandran I think) about people with agenesis of an arm or what have you, who nevertheless could "feel" they had a phantom arm. The sense of an arm, a real arm doing real things, with no prior peripheral input experience. Nothing for the brain to have worked with, except itself.

This is just page 13 of this book of 223 pages. Melzack supplies only the introductory essay, up to page 19. Already I can see that he is talking about something at least one order of magnitude beyond where my mind usually goes when I think about brain function. And I'm thinking this is where David Butler has taken off with his idea of "virtual bodies" and "virtual body parts."


Anonymous said...

I fond an archived post on neuromodulation and neural plasticity, from powerblahgrr. Just stumbled across his blog, haven't really combed through it, but he's writing at a similar level as you. Might make for a little interesting back and forth commentary.

Diane Jacobs said...

Ayesha, thanks so much for the tip and the link.

giancarlo said...

I think it's a amazing information... i would like comment too abour pain, nociceptive information and other stuffs but, i just speak spanish, im from chile and i have a poor english
anyway i will reading your comments and material.