Does the Spinal Cord Think?

In recent years we have become very interested in the ever-increasing evidence there are large complex neural networks outside the brain and autonomic nervous system. The main ones are in the intestine and the heart. These systems are so complex and well organized that some people have talked about us having a “brain” in the heart and another in the intestine. This may be a bit of an over-statement. For instance the cerebellum at the back of the brain is large and highly complex, but is so arranged that it probably cannot generate conscious experience. That particular trick needs a cerebral cortex that self-organizes, recruits new systems when necessary for some particular task and generates vast oscillations that are modulated by genes and the environment.

Now new research has shown that the spinal cord has some of those same properties that we associate with the cerebral cortex. This groundbreaking work has just been published in the journal Science, and the entire paper is available here.

So why the excitement and interest? It often astonishes me how many students who come to my lectures seem not to have a curiosity gene. And there is so much about which we should be curious. Despite the billions spent on research there is still a great deal about the human body that is not understood at all. Not small esoteric things, but huge questions.

For instance how can some people think and communicate even if most of the brain is destroyed by disease? On the other hand some people are incapacitated by the smallest lesion. I’ve taught neurology for years, in particular the art of neurological examination. I was trained by some of the best in the world, so I know how to look for subtle neurological signs. Yet I’ve seen a great many inexplicable things: I saw someone come to autopsy who had no neurological signs, but had a tumor occupying more than half of the dominant hemisphere of the brain.

Here’s another puzzle: we don’t know how humans are able to move. Our muscles are controlled by thousands of nerve cells in the brain, spinal cord and peripheral nervous system. This entire complex system must work as a whole in order to successfully generate a single motion. Yet how quickly do most children learn to stand and walk. The new research has shown that the spinal cord is not a passive signal conductor, but has instead shown that spinal neurons, while engaged in the network activity underlying movements, show irregular firing patterns similar to those seen in the cerebral cortex. Even if we repeat a certain motion with high accuracy, the nerve cells involved never repeat their activity patterns. Just the same as happens in the cerebral cortex.

This is yet more evidence to suggest that “thinking” does not only go on in the brain. It makes sense to think of the major systems – heart, intestine and spine – as key components of the subliminal, pre-conscious mind. Some people like the term subconscious, but that runs into the confusing problem of mixing up the terms subconscious and unconscious.

I talk about some of these differences and how to work these different parts of yourself in the book and CD series Healing, Meaning and Purpose.

Chiropractors have been telling us for years that the spinal cord is a lot more than just a relay system. It looks as if they may have been correct.

If you are interested in following up on my comments about what it takes for a neural network to generate conscious experiences, you may be interested in having a look at my review of the excellent new book Rhythms of the Brain by Gyorgy Buzsáki. and