Single Neuron Theory Of Consciousness

Hello, Senior at Port Townsend High School in Washington State here.

I’ve been reading up a bit on theories on consciousness, and I’ve come across a couple that worry me, hoping to get a neuroscientist’s take on this.

I read a presentation given by Dr. Steven Sevush about the single neuron theory of consciousness, stating that consciousness may be created at the single neuron level as pyramidal neurons integrate information in the brain, and I’ve been ruminating and losing a lot of sleep over this for months, thinking about this all day and such, for a few reasons.

For one, if our conscious experience is created by a single neuron or network, and there are other neurons in the brain having simultaneous experiences, wouldn’t that mean that the death of our associated neuron among others in our human bodies dying— would mean the ceasing of ourselves to exist, even if the rest of our body and the plethora of other conscious beings created by other neurons, goes on living without ever knowing at the macroscopic level from the outside?

I read that the adult human brain loses about 190,000 neurons a day. Of course, not all neurons are created equal, as some serve input purposes, some serve output purposes, some special types (like the pyramidal kind) serve both, and others exist mostly for the relaying of information. One might think that a memory cell constantly in use due to its service of core or commonly used memories would be less likely to disappear than a rarely active one. To that extent, one might surmise that a cell with many connections like the pyramidal type, wouldn’t be quick to disappear due to the body’s reliance on the type.

Another separate theory of consciousness that worries me is the idea that our consciousness is of course observably created by cells, and in a non-religious context our soul and existence is merely that of our body. If our consciousness is merely a function of the present group of neurons operating as is, and over time they’re slowly dying off and now and then a new cell or synaptic connections along dendritic trees are being made, would that mean that from the outside our body would continue on existing, our consciousness replaced by another operating as a function of our body?

I don’t mean to enter into an entirely philosophical realm here, so as to waste anyone’s time. I also don’t want to sound like I’ve lost my marbles. But I’ve been inspired by the Allen Institute’s research over the years, and this was the first place I thought to turn over this subject. If any researcher at the institute could answer my question about the single neuron theory of consciousness from a more knowledgeable standpoint of course than myself, I’d be eternally grateful. In fact— I haven’t been able to remain productive as a High School senior for months due to thinking about this all day for hours on end, losing motivation and being constantly exhausted as I’ve tried to obtain closure on this topic. It would mean the world to me if someone could help me out here. Thanks.

-Cameron Rowland

Hi Cameron,

Here’s a reply from our Chief Scientist, Christof Koch.

While individual neurons in cortex, the outermost layer of the brain, can be amazingly selective – for instance only responding to diverse images or even cartoons of a single individual – such as the famous Jennifer Aniston neurons I co-discovered – there is no evidence that the subjective feeling, he experience associated with any one such percept, thought or memory resides at the level of individual neurons. We know from neurological patients and from neurosurgical stimulation of cortex, that consciousness is associated with large collection of neurons, anywhere from a few 10,000 to perhaps millions or more for a single experience. And yes, the neural networks making up the brain adapt and change (and sometimes die) as we grow up from a fetus into an infant, a child, a teenager, an adult and so on; likewise, so does our consciousness and what we experience. Both the brain as well as the closely associated feelings are two sides of the same coin.

If you wanted to read more on this topic, you can read my popular book The Feeling of Life ItselfWhy Consciousness is Widespread But Can’t be Computed (2019).

Best

Christof Koch, PhD
Chief Scientist, MindScope Program, Allen Institute

First of all, thank you both so much for your time, it means a lot. I greatly appreciate your contributions to modern understandings of the brain and neurobiology, as well as for allowing a layman’s glimpse into the “why’s” of the brain that drive the public to want to know more. As an eighteen year old high school senior, I’ve had no formal education in these areas but have found myself learning and intrigued because of your studies.

I read your beautifully worded and well researched 2019 work, which seemed like a building-on and evolution of your previous insightful books published.

I had to ask, however— not out of doubt of your knowledge in any way, but as a clarification and more so an elaboration on the question posed.

In Steven Sevush’s work, he illustrated the hard problem of consciousness as being illusory within internal observation, as the mind— being an aggregate of neurons, could hold multiple similar conscious experiences at the single neuronal level giving the impression of a single macroscopic consciousness from the outside, due to their nature to work together in creating a single consensus of action in a single human body. The analogy he used was that of a crowd watching fireworks creating a chorused reaction of “oohs and ahs” at the macroscopic level, but being composed of several individual experiences of individual beings reacting to the fireworks independently.

Therefore, though from the outside a living being appears as one conscious experience, internally, such is an illusion as there could be many simultaneous experiences at once.

I didn’t want to believe this, and I still don’t want to, believing that any single neuron— even in the highly interconnected thalamus or claustrum of the human brain wouldn’t hold enough processing power on its own to create a subjective experience of the high-resolution and combined visual, auditory, other sensory, higher thought, and memory processes all at once, given the limits of a single neuron in integrating information from it’s dendrites.

For after all— if Sevush’s theory were true, it could mean that PERHAPS we wouldn’t continue to exist in our own bodies and experience “death” sooner than any of us thought, should the single neuron our experience resides in, die along with the other 190,000 cells we lose in a day.

The reasonable side of me wants to ignore this theory and its arguments— for after all, if it were true, there’s nothing anyone should or could do about it, and we should all be grateful to exist at all in the first place.

But the fact is— I always worked extremely hard and enjoyed doing so— figuring I’d enjoy life even more down the road, being an extremely ambitious person with huge aspirations. Now, believing I might not be around to see it, or even exist tomorrow or years in the future, it’s hard to obtain that same feeling, as well as the novelties of life such as:

“wow, I can’t believe I was really here years ago”

or

“I’m so excited to be in college next year and have a family in the future and reap the rewards of my years of hard work”

It’s the fact that I perceived the single neuron theory of consciousness as non-conflicting with the Integrated Information Theory (IIT), given that single neurons integrate information, that has caused me so much horror as of late, and my obsession to be sure that it wasn’t the case and that I was just overthinking it.

I suppose to summarize— my question is, could a single neuron have the processing power to experience so much in even tenths of a second, to create a conscious experience? And can we be reasonably sure to an extent that this single neuron theory of creating our individual experience isn’t creating an illusion of experience, rather than the entire brain ACTUALLY being a single conscious experience?

I’m sorry to take up so much of your time, and I’m sorry if this wasn’t a very cohesive reply. This whole questioning has been mentally exhausting, and I wish I could forget all of it.

To better put it— would it be possible that specific activations create a macroscopic looking experience from the outside because of cell activity, while there are several internal conscious entities? The idea would be that specific paths between neurons would activate and bring forth information— say in the case of memories being activated, but according to the single cell consciousness theory, that this information from any source is distributed to all these such “conscious” cells which individually have their own simultaneous experiences. Just wondering if that’s possible.