Reading the Nov ‘09 issue of Scientific American in post-Thanksgiving tryptophane torpor yields these developments in Spatial Medicine:
http://www.scientificamerican.com/article.cfm?id=new-culprits-in-chronic-pain
Now, this is a very exciting finding for my concept of ‘Spatial Medicine’; it is a further development from the original research reported in Sci Am in ‘The Other Half of the Brain’, referenced in Ch 1 of Anatomy Trains. It is a fact that there are nine times as many connective tissue cells in the central nervous system as there are neurons. All the research has concentrated on the electrical neurons, and almost none on the glia (meaning ‘glue’, the general name for these mesodermally-derived connective tissue cell types such as astrocytes, monocytes, oligodendrocytes, Schwann cells, microglia, melanocytes, etc.
Even this article championing glia fails to mention their now well-established role in brain structuring in embryological development (also referenced in Ch 1 of Anatomy Trains) - the glia build the neurons into a working brain. They also form the fatty myelin that insulates the nerves, and they certainly perform their traditionally assigned role of helping to supply the neurons with glucose and oxygen faster than the poor stressed-out, stretched-out, action-potentiating axons can do it themselves.
But:
Their role in consciousness has been completely ignored until recently, when their role in feeling was sketched in in the article referenced above. Now, in this article, that sketch is filled in some more (at least in my understanding) by detailing their role in chronic pain. You can read the article for the neurological loop that can sustain chronic pain long after the injury is healed; my interest here is in how the glia and neurons work together to produce the chemistry of consciousness.
As my students know, I believe consciousness is a distributed phenomenon, not localized solely in the brain. Even if we admit the brain is important (of course it is), there are thousands of miles of capillaries in the brain, and 9 times as many connective tissue cells as neurons, so all three holistic communicating systems of the body (see Anatomy trains, Ch 1) can be involved in the brain’s production of awareness. And every time they fill in the ‘how’, they seem to confirm my theories.
We have long seen the nervous system as a string of electrical wires that create the ‘computer’ of the body. Of course we know it is ‘wetware’, and that the computer model is both too durable and inadequate at the same time. For one simple thing, the ‘wires’ are not connected up, and require this seemingly inefficient chemical squirting of neurotransmitters between one axonal end plate and the next neuron’s dendrites.
‘Inefficient’ for an electrical engineer interested in speed and accuracy of transmission, but not for a biological organism with other constraints. As Candace Pert has documented in Molecules of Emotion, neuropeptides pour through these synaptic clefts, altering their ‘tone’ and setting the ‘feeling’ state for the whole set of wires, or just a local set of wires. More than 200 of these ‘messenger molecules’ have been discovered, and receptor sites for many of them have been found on all the cells of the body, not just the dendritic receptors.
So now what we see in this new research is that the glial cells, particularly astrocytes and microglia, gather around the synaptic gap, sopping up extra neurotransmitter, sometimes dispensing it out again to augment signaling. They also release growth factors to neurons that are injured, and also release signaling cytokines to bring in the immune system to fight infection or begin healing. It is when these mechanisms go wrong that a positive feedback loop can be established that implicate the glia in some persistent chronic neuropathic pain. Drugs are being developed.
Beyond the drugs, however, we see the interaction between the connective tissue network in the brain combining with the neurons to produce consciousness. I predict further findings detailing an increasingly recognized role for the glia in awareness. Less established would be some kind of communication (via the pia mater? the microvacuolar collagenic dynamic absorbing system of Guimberteau?) between the glia of the brain and the rest of the extracellular matrix that we deal with every day. But stay tuned, for such connections will be forthcoming if it is indeed that three whole networks - in other words, our whole body - that is aware.
