Saturday, April 01, 2006

Part 7: There are voices in my head

Suppose that consciousness exists in the brain. Clearly, the brain has many other functions, most of which have nothing to do with experience or decision-making. Then why is it that some neurons cause consciousness to appear, while the others are merely pattern recognizers? If you think of Jeff Hawkins' six-layer cortex hierarchy, what is it that sits at the top of the topmost layer and experiences the world around me through the streams of abstract concepts that propagate up from my eyes, ears and other senses? What is it that decides what I am about to say next? Whatever it is, it is probably inside my neurons, but which ones? Why those ones? There is the problem of deciding which neurons are conscious and which ones are merely information processors. How do these neurons communicate with each other?

Dr. Steven Sevush, an Associate Professor of Psychiatry and Neurology at the University of Miami has an interesting solution - the single-neuron theory of consciousness. Sevush proposes that there is no fundamental difference between the "conscious" and the "non-conscious" neurons. In fact, all neurons are conscious - every single one of them. However, some are lucky enough to be located in a special area of the brain, the left lateral prefrontal cortex (PFC), where the outputs they produce directly affect my motor functions. Sevush refers to several experiments and argues that if there is an area of the brain where consciousness sits it is in the PFC. There, things get strange.

First of all, the neurons in the PFC are quite complex. Some have tens of thousands of connections to other neurons. Second, there is a substantial degree of interconnection between the PFC and Broca's area, which is responsible for speech and comprehension. Sevush argues that each of the neurons in the PFC receives inputs and produces outputs that are complex enough to account for the whole of our conscious experience. Each neuron is capable of being conscious on its own.

If that is true, then perhaps the brain does not simply have a single consciousness. There could be hundreds or thousands of conscious neurons, each one experiencing and interacting with the world independently. Since each of them receive almost identical inputs, they each produce very similar outputs, and it is the amplification achieved through the strength in numbers that is responsible for that which we percieve as a single consciousness.

Sevush gives two analogies. Consider a crowd watching fireworks. Each member of the crowd sees the fireworks independently and reacts with an "aah" or an "ooh". At a distance, one person would be inaudible, but the collective response of the crowd as a whole can be heard as a distinctive "aah" or "ooh". The crowd is an entity that reacts to the fireworks display, but the crowd's consciousness is nothing more than the combined consciousness of the individuals in it.

As an example of a response, Sevush cites Garry Kasparov's 1999 chess match against the World, where the grandmaster played a single game against a large number of opponents on the Internet. The World's moves were decided by a majority vote.

The single-neuron theory claims to be an alternative solution to what is called the binding problem: how do the huge number of neurons work together to produce a unified conscious experience? Basically, there are three possible answers. First is the neural network approach, which postulates that neurons work together synchronously by exchanging complicated non-linear signals, and consciousness emerges as a property of the whole structure, not of any single neuron. Like any emergent theory, it has its opponents. Second is the Daniel Dennett approach, which states that consciousness is an illusion, and what in fact goes on in the brain is far from being unified or coherent. We will come back to Dennett's ideas later. Finally, here is the single-neuron theory, which side-steps the binding problem by saying that each neuron is fully conscious on its own, and that which we percieve as the consciousness of a human being is the collective sum of the conscious experiences of a large number of individual neurons. Most of those neurons receive identical inputs and produce identical outputs, and sproradic errors from stray neurons are corrected by adding together the signals produced by all of the neurons - a simple, linear operation.

Sevush then goes on to speculate about possible experiments that could prove or disprove the single-neuron theory. The presence of complex neurons in the PFC, each one capable of receiving very complicated inputs from all areas of the brain, would give evidence for this theory, as would the presence of multiple such neurons, each receiving identical inputs and producing identical outputs. There is no experiment, however, that could prove the single-neuron theory correct - only ones that would give evidence for or against it.

So how could a single neuron posess a degree of consciousness that is as complex as the consicous experiences of a whole human being? The rest is pure speculation. It could be that quantum effects, similar to those of Penrose and Hameroff are relevant here. In fact, the quantum connection becomes more believable on the scale of a single neuron. There is no longer a need to maintain particles in quantum entanglement across several neurons, only within a neuron. This is still, however, a huge distance for quantum entanglement.

On the Consciousness DVD, Sevush goes further to make a speculative connection with string theory. A beautiful result that comes out of string theory (if it is true), is that nothing can be smaller than a string. This claim is not to be confused with similar claims that have been made about molecules, atoms and quarks. It is inherent in the mathematics of string theory that if we consider lengths that are smaller than the length of a string, then the physical equations "flip" inside out, and we get identical physical laws that hold at those scales. It is as if each string had a whole world inside of it. If that were true, then, Sevush argues, each molecule in each neuron could be conscious, too, and so would each atom in a molecule. Finally, each string of each atom inside me would be conscious and have the same conscious experiences as me as a whole. If every string is as complex on the inside as the whole universe is, then it is certainly complex enough to be capable of my conscious experiences.

It is easy to get carried away in speculations, so let me summarise the key premise of Dr. Steven Sevush's single-neuron theory. Each neuron is capable of fully complex human conscious experience. There is a collection of specially (luckily) positioned neurons in the area of the brain called the PFT which are responsible for our consciousness. Those neurons receive identical (or nearly identical) sensory inputs and do not communicate with each other in producing (nearly identical) outputs. The only cooperation that happens is a big summation of their outputs, which serves to (1) minimise sporadic errors from stray neurons and (2) achive signal amplification levels sufficient to control our speech and motor functions. What we percieve as a single conscious person is instead a collection of multiple conscious entities (the neurons) that combine their outputs and "vote" on each decision.


At 1:31 PM, Blogger Kurt said...

I thought Dr. Sevush's interview was one of the highlights of the Consciousness DVD. I don't think his comments on the neural organization in the brain were particularly remarkable, but I do think his line of reasoning could be taken as a good case for panpsychism. But the thing that really struck me was his delivery. He talks in a perfect monotone, not in the dull, boring sense of the word, but in an almost trance-inducing way. I could n't help thinking that he would make a great hypnotist. Either that, or maybe he's one of those zombies that philosophers debate about. Anyway, his talk was one of the few that I felt compelled to replay and watch again.

BTW, Daniel Dennett was interviewed by Bill Moyers on the Charlie Rose show last night, not about consciousness but about his new book on religion, "Breaking the Spell".

At 4:57 PM, Blogger Evgueni Naverniouk said...

I'm glad to see Part 7 up. Been waiting for some time.

The only problem I have with Dr. Sevush's theory is that it involves the neurons "voting", which to me is hardest to imagine. Who then "counts the votes"? It's really confusing.

At 5:05 PM, Blogger Abednego said...

The voting is not a problem at all. Think of it as a crowd of people, all yelling either "Yes" or "No", but the majority of them are yelling "Yes". Then if you stand some distance away, you will hear a "Yes". No one is doing the counting; the answer is just obvious because there are many more "Yes"s than "No"s.

At 5:19 PM, Blogger Abednego said...

Kurt, I agree about Sevush's interview on the DVD. After 10 minutes of listening, I got into the same state of trance that he seemed to have been in. The monotonous, soft voice; the lack of interruptions from the interviewer... I was just nodding along, buying everything he was saying. Very hypnotic.

After thinking about it for a bit though, I came to the same conclusion as I have about most of the other theories of consciousness. Yes, he makes a good observation that each neuron could be conscious on its own, and that we should seek the answer to the "hard problem" not in the structure of the brain, but in the structure of the neuron. On the other hand, he is just deferring the answer by pushing it to a smaller scale, just like Hameroff.

Of course, he admits this and offers some speculations at the end of the paper - the quantum stuff again, and the string theory, but it all just seems like silliness to me; "explaining" consciousness in terms of the newest and least understood theory of physics.

That said, Dr.Sevush really does try hard to stay as scientific as possible, and he admits all of the places where he has made assumptions and even offers some experiments that could disprove his theory. That's commendable.

At 8:34 AM, Blogger Arthur said...

To my way of thinking, consciousness is more of an activity (of the searchlight of attention) than a specific locus. In my programming of Mind.Forth it has recently dawned on me that initial damping of just-thought-concepts, followed by their gradual decay into zero activation, may constitute a moving wave mechanism of consciousness.

At 9:07 AM, Blogger Triggur said...

I still don't buy the single-neuron vote tabulation notion; it just defers the final seat of consciousness to some outside observer averaging all the signals down. If "you" experience the averaged signal, what is interpretting it?

At 9:38 AM, Blogger Abednego said...

Well, the claim is that the voting stage is automatic. If the "let's go left" neurons outnumber the "let's go right" neurons, then your legs listen to the "let's go left" side, just because they are louder. There is no interpretation going on.

I'm not saying I buy it either. I believe things are a lot simpler than this.

At 6:56 AM, Blogger Harrison said...

I can see how the single-neuron explains what we see, but I do not see a basis of which Dr. Sevush could propose this idea on. There does not seem to be evidence (that I know of) that can suggest such a theory to be proposed in the first place.

I recognize in the importance of the need of a basis for which to propose an argument. Consider this statement: "There is a pink unicorn right now behind you, but it is invisible, cannot be detected in any way, and it cannot cause any detectable change in this world". It explains for itself, and cannot be disproved. However, just like the single-neuron theory, it cannot be proved, and further more for this statement at least, there is no initial evidence to suggest it.

Just a thought.

At 6:58 AM, Blogger Harrison said...

Oh and I forgot to say that the example I gave is very exaggerated I do realize. But in concept what is the difference between that and some theories such as the single-neuron theory?

At 1:53 PM, Blogger Abednego said...

I don't think it is necessary to have a "basis" to propose a theory. A good theory should be simple and testable (and hopefully, correct). The single neuron theory is simple in the sense that it avoids the complicated issue of communication - how do neurons talk to each other? It is not easily testable though, and that is my main objection.

At 8:54 AM, Blogger Harrison said...

I feel that the need for a basis in which to propose an argument is made very clear when in debates involving hard to prove things, such as religion.

I have been in religious debates against cult groups, whose systems attract millions of people to live by their ways, and devote their lives to the cult. Many cults make very outrageous statements, in which, there are no ways to disprove. For example, the Heaven's Gate cult performed a mass suicide one day in a square, believing a UFO was flying past that moment and would pick them up. When people claimed that radar would detect the UFO's, more statements were added by the cult leader (and accepted without hesitation from followers) making reasons why the UFO cannot be detected in any way, basically.

How can you prove that wrong? You cant. You must rely on the fact that there was no basis, AND the fact that the religion does not explain a great deal about why it works, relying on trust in the cult.

I find Dr. Sevush's theory very weak, becuase there is no basis for the argument. It almost seems like he first 'guessed' (no connotation here) the fact Every single neuron is conscious and added stuff around it so it would make sense. Or at least to my understanding. I find that first statement very bold, considering what little we know about how neurons work, and the fact that Sevush doesnt even attempt to explain HOW each individual neuron can attain consciousness.

Ive read some stuff about this theory, but nothing in depth. If theres anything I forgot to consider please point that out.

At 1:42 PM, Blogger Abednego said...

After foolishly trying to have a logical argument with religious fanatics, I came to the obvious conclusion that it's pointless. In my view, all religion is anti-science, by definition. Even the most open-minded religious people will tell you that religion is about believing something. Whether it is Jesus, Allah, the spirits of your ancestors or aliens, you have to believe something. Otherwise, there is no hope.

Science, on the other hand, says that you have to believe nothing! Anything anyone tells you is up for a discussion. It doesn't matter how old or wise that person is; nothing they say is the absolute truth. Question everything, test everything, always try to disprove your beliefs. That is the only way to find the truth, says Science.

When you have such a fundamental disagreement about the very principles of the debate, there can be no reasonable discussion between a skeptic and a religious fanatic. The skeptic will try to use logic to prove something and get at the truth. The religious person is not interested in logic and argument and will quote an ancient text as the absolute truth that is not up for debate. Some things are off-limits and are not to be questioned.

So I've stopped trying to debate the existence of God. Logically, the debate is over: there is no proof that God exists - therefore, he doesn't. Simple. Any debate beyond this point is not logical, and I don't know how to participate in illogical debates. Don't get me wrong. I am not certain that there is no God. I cannot prove it. As soon as somebody shows me a compelling piece of evidence that I'm wrong, I will reconsider my position. Until then, I'm sticking with the simpler theory. I am trying to be a scientist. I have no unquestionable, absolute beliefs. I have never heard of a logical argument for the existence of God (Descartes was royally confused), so I've given up debating the issue until such an argument appears.

At 5:27 AM, Blogger James said...

consciousness as an illusion:

conclusiveness = continuous interaction of a need(driver) to do/achieve something with a knowledge database.

The fact that we cannot stop thinking creates the illusion that we (our consciousness) exists.

By the way, the driver/need is directly or indirectly linked to the part of the brain that create our most basic emotions.

I'm just trying guys. Does it makes any sense?


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