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So far we have been discussing the nervous system as an input/output system. In this model, neurons have served as “boxes” and glia as wires connecting these boxes. However, recent advances in the neurobiology have complicated this picture. In a 2004 article in Scientific American “The other half of the brain: mounting evidence suggests that glial cells, overlooked for half a century, may be nearly as critical to thinking and learning as neurons are,” author R Douglas Fields discussed the significance of glia in the nervous system. Formerly associated with maintenance and support, there is now evidence to suggest that neurons and glia “talk” with one another.

“Glia influence the formation of synapses and help to determine which neural connections get stronger and weaker overtime; such changes are essential to learning and to storing long-term memories. And the most recent work shows that glia also communicate among themselves, in a separate but parallel network to the neural network.” (p.55)

If this recent work is true, it has profound implications for the development of input/output models of the nervous system. It also offers explanations that could account for the Harvard Law of Behavior. Should we think of two sets of input/output system tied together each offering feedback for the other with one set for neurons and glia respectively?

Neurons have been the actors on under the stage lights garnering most of the attention from scientist in the audience, but glia are not merely the unneeded stage hands. Outnumbering mainstage neurons by nine to one, glia also help actors who have forgotten their lines. By communicating with neurons and with each other through chemical signals, glia can also help guide axon regeneration and formation of synaptic connections, suggesting that a more apt description of glia would be unseen directors who insure that neurons function effectively.

In short, glia may play a crucial role in the formation of memories, in the way we behave and in the way we learn, (Einstein, for example is know to have had a unusually high concentration of glia in the association cortex part of the brain.) This forces us to ask new questions. Can we explain the 10% of animals who respond differently to the same stimuli to input received by neurons from glia? If so, how should we adapt our input/output model? Shall we simply apply integrate two sets of input/output systems?

“The other half of the Brain: Mounting evidence suggests that glial cells, overlooked for half a century, may be nearly as critical to thinking and learning as neurons are.” Scientific American March 22,2004 p.55