A Theory of Consciousness

Lately, I’ve been reading Oliver Sacks’s new-ish book Musicophilia. While it’s not quite the tour de force that The Man Who Mistook his Wife for a Hat was, it’s gotten me thinking once again about the neurology of consciousness, and after a few days’ contemplation (and a few years spent reading neurological books), I think I finally have a rough sketch for my own theory of how consciousness comes into existence. Of course, I’m not a neurologist. I don’t know the details of how all this works, and none of it is based on empirical evidence, but that’s the beauty of the Internet: you can talk about ideas abstractly. And, since that’s what I’m good at, that’s what I’m going to do. So, here goes: consciousness.

There are a few structures which are vital to conscious experience. These are:

  • The thalamus
  • The brainstem
  • the prefrontal cortex (and the rest of the cerebral cortex as well)

The other structures are more involved in the contents of consciousness. They are the raw material that the conscious structures process. Here’s how it seems to me that consciousness happens:

  1. Sensory information enters via the brainstem.
  2. The brainstem preprocesses the information and sends it to the thalamus.
  3. The thalamus takes in the preprocessed sensory information and combines it with information about the state of the cortex itself.
  4. The thalamus relays this information to the relevant cortical structures. The prefrontal cortex may play a role here in organizing the arrival of the information, and perhaps in weighting it emotionally.
  5. The cortex processes the sensory information, and the prefrontal cortex reads the results and generates judgments based on emotional weighting from the limbic system. It may generate some of its own emotional reactions as well.
  6. The prefrontal cortex sends the interpreted brain state back to the thalamus. There may also be other loops between the thalamus and the other cortical regions.
  7. The processed mental state enters the thalamus, along with a new set of sensory information.
  8. Repeat.

Of course, this says nothing about memory formation, which is very important for making sense of conscious awareness. It just so happens that I have a theory for how memories form as well.

  1. An emotional signal is sent by the amygdala (or some other part of the emotional system) to the hippocampus, which “reads” sensory information currently being process, thus forming connections between the disparate kinds of information.
  2. This association is stored in the temporal lobe. When the area where the memory structure is stored is activated, the temporal lobe re-activates the relevant structures (those whose particular activity patterns were linked by the hippocampus), and the remembered event is re-experienced.

I’m not really sure how a memory would be recalled in this model, though. I’d venture to guess that it’d have something to do with the prefrontal cortex sending a signal to the temporal lobe, in order to retrieve the memory for comparison to current events.

This little model (and I’ll say it again, I’m not a neurologist. Not even close, so think about this model in the spirit in which it was intended: as a useful idea, not as anything approaching a theory) does shed some useful light on certain kinds of mental illness and the effects caused by certain sorts of brain damage.

  • Schizophrenia: It’s well known that in schizophrenia, the prefrontal cortex is not functioning as it should. Without a properly-functioning cortex, judgments based on memories and sensory information cannot be made properly, and sensory information does not get integrated properly. Also, the prefrontal cortex’s inhibitory connections are less functional as well, which would seem to explain not only the disorganized and unintegrated thought patterns associated with schizophrenia, but also the hallucinations, which could be the result of sensory information going to the wrong place or being integrated improperly. Or, perhaps, the hallucinations and delusions might have something to do with the fact that, without prefrontal cortical direction, the various cortical structures can no longer properly regulate their output.
  • Anterograde amnesia: with damage to the hippocampus comes difficulty forming long-term memories. In this model, that would be because the structure which associates the various neural states with one another is either incapable of doing so, or else it is incapable of moving them into the temporal lobe for permanent storage.
  • Thalamic coma: this may also apply to comas in general, as well as minimally-conscious states, but thsi model only really has something to say about thalamic comas. When the thalamus is damaged, not only can external sensory information not enter the cortex, but the cortical state itself is also prevented from being communicated to the cortex, so there is an absence of both sensation and cognition. The thalamus, however, is divided into two parts, one of which communicates primarily to the cortex, and the other of which is mostly responsible for preprocessing and relaying sensory information. If only the sensory-preprocessor (in the case of vision, this is the lateral geniculate nucleus) were to be damaged, the patient would still likely be able to achieve conscious awareness, but there would simply be no sensory information for them to process.
  • Encephalitis lethargica: in patients with this disorder (which is, according to Oliver Sacks, an extreme form of parkinsonism), the patient is mostly functional, but they are unable to initiate much activity (if any). In this model, that would be because of damage or inactivity of the limbic system, which is crucial in communication emotional meaning to the prefrontal cortex. In patients with severe parkinsonism, there may be difficulty seeing the relevance of actions, and therefore, the actions are not generated. This can also occur with certain kind of brainstem and prefrontal lesions.
  • Depression: in this disease, the prefrontal cortex is known to be less active. However, unlike in schizophrenia, its integrative functions must still be intact. However, its emotional functions become impaired, leading to difficulty forming memories (since the PFC cannot communicate the emotional necessity of remembering something to the hippocampus, and would likely have difficulty sending retrieval signals, too), lack of motivation (since the significance of actions would become unclear), and depressed mood or flat affect (since everything would have the same emotional significance).

I won’t go any further, for fear of over-inflating my ego and for starting to make claims that I have no hope of arguing for. But this, I think, is at least something to get people thinking. Of course, there are a billion things that I haven’t taken into account: the left versus right hemisphere functional disparity, the effects of neurotransmitters, and no doubt I’ve left out quite a few very important brain structures.

New Short Story: “The Long Wait”

After a few days’ work, I’ve finally finished another short story. Lately, I’ve been getting the disturbing feeling that, if I keep actually finishing stories like I’ve been doing lately, then I might set a precedent and accidentally amount to something.

Anyway, enough disjointed self-deprecation. I present to you: The Long Wait. It tells the story of Derek, who’s spent the last ten years trying to escape from the Harvesters, even though he knows they will find him eventually. As he wanders through the desert, trying to scratch a living out of the sand, his life becomes an a miserable burden, and he begins to wonder if there’s any reason to go on living.

(Beware: Existentialism ahead!)

Exhaustion

I haven’t really written anything of consequence for a while, and for that, I apologize. Let me explain.

For the last two or three weeks, I’ve been sleeping pretty damn badly. Every morning, at around 5 or 6 A.M., I find myself awake, and usually, unable to get back to sleep. I have no idea what’s going on, but with final exams looming, this is about the worst time that this could have happened.

The result is that I am completely and utterly exhausted. I feel stressed and moody, and generally just lousy. I’m hoping this will clear up in a week or two, and when it does, I’ll be back writing again. Until then, I may publish one or two of the posts I wrote but never released.

Cartoon Me

Greg Williams, a cartoonist for the newspaper The Tampa Bay Observer, is certainly moving with the times. He draws a comic called Blogjam for the Observer based on blog posts from various sources. He took an interest in my long-ago post about the helium shortage, and turned it into a comic. The result? A delightfully-illustrated comic of the post, including a cartoon version of me!

Helium Shortage

You can see the comic here. And be sure to check out some of Williams’s other comics here. And I’m not just suggesting that because he drew me as flatteringly less scruffy than I actually look in real life, but because it’s actually an interesting and well-executed series he’s got going there.

10,000 Views!

I can’t believe it. It was only a few months ago that I was celebrating my 5,000th view. I guess my intuition was right, people are more interested in blogs that actually talk about something interesting, rather than just blathering on about the weather. You’d think I would have figured that out before now.

Anyway, in celebration of my 10,000th view, I give you: every number less than or equal to 10,000, with the primes highlighted. Yes, I know I’ve done an image like this before, but I thought it would be fitting.

Many thanks to all of my 10,000 readers thus far, and thanks especially those of you who were nice enough to leave all those encouraging comments!

And here’s hoping for another 10,000!

Visual Numbers #2

Factors: The numbers from 1 to 500 are plotted horizontally across the top row. Along each vertical column, if N divides the number X (represented here by distance across the top row) evenly (that is, if N is a factor of X), then the pixel N pixels down from the top is black.

Prime Factors: The same general principle as above, but in this image, only the prime factors are shown.

Blue Over Yellow: Basically, a combination of the previous two images. Numbers from 1 to 250 are plotted horizontally, and factors are plotted vertically. If a factor is prime, the little square representing it is blue, otherwise, it’s yellow.

That tantalizing structure is still just slightly out of reach…Oh well, back to work!

Visual Numbers #1

This is the beginning of what I hope will be a fairly long-running series of posts, each containing one or two (or three, if I’m feeling adventurous) numerical or mathematical visualizations. If you need a concrete example of what I’m talking about, just check out the image here).

Anyway, here goes:

Meet the Primes: Every pixel represents a number from 1 to 250,000. The image wraps horizontally; that is, the first pixel of the first row is the number 1, the first pixel of the second row is 501 (since each row is 500 pixels wide), the first pixel of the third row is 101, and so on and so on. Pixels representing prime numbers are black. From this view, it’s quite obvious that there’s likely some sort of structure to the primes, but it’s hard to say what that structure might be.