The Neuron Doctrine

The "Neuron Doctrine" is a neuroscience theory determined by Santiago Ramon y Cajal (he won a nobel prize for his brilliant work with neuronal circuit mapping) which states that the interactions between neurons are the sole constituents of human thought. Since twenty years ago, however, scientists began to question this theory - their trepidation founded upon the fact that neurons only make up approximately 10% of our brains. The other 90%? Our glorious glial cells.

Just as we've discussed endlessly the advantageous and very recent discovery/acceptance of the glymphatic system, glial cells were previously neglected or rather overlooked due to the belief that they possessed little, if any, vital functions to the nervous system. Scientists knew they were there, but it seemed almost foolish to them the idea that one ought to explore other parts of the system besides neurons. Neurons were the "functional units" - the all stars, right? Not quite. The tricky thing about glial cells' earlier neglect in the science world is that whenever scientists studied neurons, they always knew that the neuron had to be sitting in a bed of glial cells in order to survive for experimentation/observation. That's when a man named Stephen Kuffler decided to be unsatisfied with this discrepancy. He asked a very important question and it has served the fame of glial cells everywhere. Kuffler decided to test the Neuron Doctrine by replicating the result of neuronal activity (potassium excretion) and looking at the way in which glial cells would respond. As a person who had previously agreed with the Neuron Doctrine, Kuffler expected this experiment to confirm glial cells as nothing more than insulators for neurons (that would mean no reaction from the glial cells after introducing potassium to the cells). But much to his delight at finding a new piece of the puzzle, Kuffler found that the glial cells were stimulated by the potassium. The astrocytes were found to mimic the chemical mechanisms of neurons with a change in electrical potential as a response to potassium.

The resulting reaction, an alteration of electrical potential, isn't simply that. In responding to potassium excretion, glial cells produce a massive ripple effect known as a "calcium wave," spreading from the point of stimulation of one astrocyte to all other astrocytes in an area hundreds of times the size of the original astrocyte. Now, if that doesn't make glial cells functional components of the brain, I'm not sure what would. Although these findings in no way disprove the many equally important functions of neurons themselves, they certainly beg the question of which cell insulates the other? Beyond this physiological query however, let us return to the Neuron Doctrine I mentioned earlier. If neurons are the only cause for our thoughts and neurons only make up 10% of brain cells, then where do the other 90% fit into the picture? To answer that question, it may likely take another twenty years but the first step is really gaining a clear understanding of the implications behind cell activity such as calcium waves. Sometimes, calcium "puffs" can be released from astrocytes without any external stimulation, this causes waves that are similar to the glial responses to potassium stimulation. Some scientists have perceived this to cause the random thoughts we have during dreams or sensory deprivation experiences. Although I haven't really read this much throughout the literature, I'm thinking maybe the fact that the glymphatic system only works while we are asleep has something to do with those calcium "puffs" and our dreaming... maybe Silma can help us with that one. In reading all of this literature about glilal cells' purpose and functions however, I noticed one large emergent question - "Do our thoughts and imagination result solely from glial cell function, solely neuronal function, or an interaction between both?"

It's a loaded question, no doubt. But it kind of brings me back to a couple journals back when I was discussing why glial cells are important and how they fit into the narrative of neuroscientists always returning to the question of how we exist in the biologically complex way that we live. If you recall, I continuously mentioned that glial cells don't really seem all that important until we start seeing their dysfunction. I think I'm going to take that statement back, I may have been jumping to conclusions there. An exploration of the "Neuron Doctrine" has certainly begged to differ - glial cells are certainly of interest outside the realms of disease. Although it often takes a long time for neglected cells or components to be thoroughly studied, I think the drive to be curious about something and explore it further can also come from a discrepancy or gap in someone else's knowledge. We all think differently for a reason. I mean sure, a crippling and devastating disease can give someone the desire to explore and cure it, without a doubt. But when we all do this thing called analysis - when we dive into the thoughts and conclusions of others, we are each always a set of fresh eyes that will find something different to grab our attention. Cajal came up with the "Neuron Doctrine," an insanely large feat in and of itself, but that doesn't mean Kuffler didn't have any questions about those conclusions. Much in the same way that science can advance based upon humanitarian needs, it can also see leaps and bounds based upon the power and strength of mere questions.