Friday, October 14, 2005

Neuromatrix 2: Outline of the Theory

(R. Melzack in Topical Issues in Pain Vol.3, page 13):

Outline of the (neuromatrix) theory
The anatomical substrate of the body-self, I propose, is a large, widespread network of neurons that consists of loops between the thalamus and cortex as well as between the cortex and limbic system. I've labelled the entire network, whose spatial distribution and synaptic links are initially determined genetically and are later sculpted by sensory inputs, as a 'neuromatrix'.

The loops diverge to permit parallel processing in different components of the neuromatrix and converge repeatedly to permit interactions between the output products of processing. The repeated cyclical processing and synthesis of nerve impulses through the neuromatrix imparts a characteristic pattern: the 'neurosignature'.

The neurosignature of the neuromatrix is imparted on all nerve impulse patterns that flow through it; the neurosignature is produced by the patterns of synaptic connections in the entire neuromatrix.

All inputs from the body undergo cyclical processing and synthesis so that characteristic patterns are impressed on them in the neuromatrix. Portions of the neuromatrix are specialized to process information related to major sensory events (such as injury, temperature change, and stimulation of erogenous tissue) and may be labelled as neuromodules, which impress subsignatures on the larger neurosignature.

The neurosignature, which is a continuous outflow from the body-self neuromatrix, is projected to areas in the brain - 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.

Furthermore, the neurosignature patterns may also activate a neuromatrix to produce movement. That is, the signature patterns bifurcate so that a pattern proceeds to the sentient neural hub (where pattern is converted into the experience of movement), and a similar pattern proceeds through a neuromatrix that eventually activates spinal cord neurons to produce muscle patterns for complex actions.

The four components of the new conceptual nervous system, then, are
1. the body-self matrix;
2. cyclical processing and synthesis, in which the neurosignature is produced;
3. the sentient neural hub, which converts (transduces) the flow of neurosignatures into the flow of awareness; and
4. the activation of an action neuromatrix to provide the pattern of movements to bring about the desired goal.

I find this information very intriguing. I'm so glad that Melzack has moved beyond TENS (Transcutaneous Electrical Nerve Stimulation).

It seems to me that by moving up into the brain he is making room in theory, in science, for what WE do, PTs... particularly those of us who treat hands-on (!) ..a fourth category he neglected to mention, that should be right in there with injury, temperature change and erogenous stimulation. WE modulate inputs etc. but with our HANDS, voices, ideas, presence, not with TENS, meaning that the brain will never adapt because the input will always vary according to what the output (inherent tissue motion or body movement) is, and will never be the same twice, unlike TENS. Take pain for example. Another nervous system (the therapist’s) functioning at a more ‘coherent’ (less painful) level will out-modulate inputs better than any TENS unit. Any day. I’ll lay odds on that.

So maybe what we are actually doing at the finer levels of brain function, is creating "a major sensory event", producing new "neuromodules, which impress subsignatures on the larger neurosignature." I quite like the idea that with treatment, my hands on someone's body creates a major sensory event that can in turn produce a neuromodule which can impress a subsignature on a neuromatrix. Hmmnn... really like that idea. (How can you tell I've rolled this over and over in my mind?)

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