What role do brain structures play in the emergence of consciousness?

[Dissident Dan]

What gives rise to what we call consiousness? As I can't think of a better definition of consciousness than subjective experience (emotion, feeling), we can use that unless someone comes up with something better.

What functions and structures of brains yield or are associated with consciousness? Is there anywhere in the animal kingdom where we can make distinctions between consciousness, unconscious, and perhaps semi-conscious (if that makes any sense)?

I am interested in a scientific discussion of neurology.

 

[Dissident Dan]

I am also interested in the evolutionary aspects of this.

 

[loseyourname]

Looks like no one else is. Seriously, though, I can post a couple of things, but not much research has been done on this. I suggest you go to Science and Consciousness Review, where they the small amount of information that is available on this topic.

I agree with you that it is a very important topic. It is unfortunate that science has all but ignored it for so long.

 

[Imparcticle]

As I can't think of a better definition of consciousness than subjective experience (emotion, feeling), we can use that unless someone comes up with something better

And what is the root of emotion/feeling? thought. I believe that is an improved definition of consciousness.

 

[Moonbear]

I wasted over an hour of my life today listening to a philosopher talk on this very topic. At least the resultant discussion among the scientists present made it worthwhile.

Science hasn't ignored the question. In fact, it's pretty much a given among neuroscientists that consciousness has a neural basis. It seems it's the philosophers who are still stuck in a rut trying to distinguish some sort of mind/brain dualism, or the theists who think the soul is separate from the body.

The real problem is the lack of a clear definition of consciousness and our limitations in how we can measure it...we have to rely on an output of that consciousness...an action, a spoken accounting of the memory of something, a numerical ranking of a sensory experience...none of these are ideal. To me, consciousness is a collection of sensory experiences and the response to those experiences that occurs in the cortex of the brain. The cortical response distinguishes consciousness from other responses such as reflexes or autonomic functioning of our body, of which we are unaware. Awareness of something requires involvement of the cortex.

In terms of identifying scientific literature on the neural basis of consciousness, you're not going to find it by looking up the term "consciousness". That, much like trying to define "spam" or "pornography", is something that has too much of the "I know it when I see it, but don't know how to define it precisely" stigma attached to it. Instead, you will find much about specific aspects of consciousness...sensory perception, speech and language development, learning and memory, motivation and reward, etc.

 

[loseyourname]

The best studies you might find are analyses of brain wave patterns during sleep and during waking states. These can at least point to the portions of the brain that are responsible for our self-awareness. I hate to do this again, but I'll post what I can find later. I'm on my way out to eat right now.

 

[Moonbear]

Actually, I don't think sleep/wake studies are going to give you any answers on consciousness. Afterall, you're not "unconscious" when asleep. It's possible we are more aware of our environment than we remember when we're asleep. If we weren't aware of our environment while sleeping, then thunderstorms wouldn't wake us, neither would alarm clocks for that matter. Ever fall asleep with the TV on only to incorporate what's on the TV into your dreams? So, even though we might not remember what happened while we were asleep, it doesn't rule out consciousness.

 

[zoobyshoe]

No one knows how, but the where of consciousness is known, and that is in the Thalamo-cortical circuit of the brain.

The thalamus is an extremely important part of the brain, kind of a grand sentral station through which almost all sensory imput is routed when it comes into the brain via the nerves of the senses.

During a specific kind of seizure, the absense seizure, the only part of the brain affected by the seizure activity is the thalamo-cortical complex, and when this happens the person's consciousness just completely shuts off, without any other brain functions being affected. Absence seizures usually only last a few seconds. The person's consciousness shuts off, they stop everything, staring blankly, then their consciousness comes back on. They are aware there has been a leap forward in time as if as few seconds of a movie have been cut out.

NOVA Online | Secrets of the Mind | The Electric Brain
Address:http://www.pbs.org/wgbh/nova/mind/electric2.html

 

[loseyourname]

It's hard to pin down certain actions that are conscious and others than are unconscious, given that there are many acts that are normally unconscious that we can become conscious of. The same thing with memory. I think we have a pretty good idea of what memory is and where it is located, but why is it that we are conscious of any given memory at any given time and not another? Does anyone here know?

Reflexive responses can also be brought under conscious control, or many of them can be. From what I've read in intro texts, the prevailing idea seems to be that consciousness is a scanning mechanism of some sort that can focus in on any given part of the brain at any given time. How is this controlled?

Also, with the sleep/wake studies, what I meant is that in sleep we become unaware of sensory input, whereas when awake, we are aware of these. This can help with determining what causes the awareness.

 

[spuriousmonkey]

I am also interested in the evolutionary aspects of this.

Maybe consciousness arose in conjunction with increased communication. How can you be aware of yourself if you have nothing to compare yourself too? Communication with others would be needed to analyze what kind of place you take in in this universe.

 

[zoobyshoe]

How can you be aware of yourself if you have nothing to compare yourself too?

There is a neurologist at the University Of California, San Diego named V.I. Ramachandran, who occasionally appears on educational channels here talking about various aspects of neurology. In one lecture he strongly made the point that consciousness is dependent on differences. He pointed out that perception of the difference between one phenomenon and another, be it light and dark, silence and sound, green and red, soft and hard, etc. is at the heart of all awareness. He would agree that being aware of yourself is essentially dependent on percieving a difference between yourself and something else. His broader message is that awareness of anything depends on percieving a difference between it and something else.

His conjecture was that, in evolutionary terms, individuals born with finer abilities to distinguish between more subtle differences were better able to hunt and gather food, and stay away from danger. Being healthier and longer lived they procreated more.

 

[loseyourname]

Some of you, if you haven't already, should check out the consciousness discussions they have in the philosophy forums. The contrast is amazing.

 

[selfAdjoint]

Yeah, well this is a biology forum, and this kind of discussion is appropriate here. If you post this kind of material on the philosophy boards someone will come along and say "But how do we know anything exists?' or "Science says consciousness is unphysical." And the thread will go away with everyone's pet fantasy.

 

[SamLuc]

LOL
As someone who spends a bit of time in PhilosophyForums.com, yeah, I know what you mean.

 

[Dissident Dan]

Does anyone have any good links to good studies on consciousness?

I would appreciate links to information that isnt' written with the assumption that consciousness is solely human or even solely mammalian.

 

[spuriousmonkey]

His conjecture was that, in evolutionary terms, individuals born with finer abilities to distinguish between more subtle differences were better able to hunt and gather food, and stay away from danger. Being healthier and longer lived they procreated more.

Then you would expect that our senses would also have evolved to a different level. We do have not very good smell, eyesight, or taste etc. An increase in the capacity of you senses would make more evolutionary sense if this concept is true than developing consciousness and a big brain. Big brains are expensive to operate. They cost a lot of energy. A better nose doesn't cost so much.

Also the in general intelligence is found in intricate and complex social communities in the animal kingdom. There is certainly a connection between social structure and intelligence. A single step further from intelligence could be consciousness.

I think the concept is touched upon in Daniel C Dennets book, 'freedom evolves'.

 

[selfAdjoint]

We have excellent eyesight in comparison with other animals. It's not just far sight, where the eagle beats us, but generalized sight that enables us to spot subtle clues in a prairie environment. We're good at what our ancestors found it necessary to be good at, and not good at things like smell, that didn't loom large in their needs inventory.

 

[loseyourname]

We're also good at creating machines that can sense things an eagle could never even dream of.

 

[loseyourname]

Does anyone have any good links to good studies on consciousness?

I would appreciate links to information that isnt' written with the assumption that consciousness is solely human or even solely mammalian.

I don't think any serious biologist believes that consciousness is confined to humans. In fact, most of the studies I've heard of have been conducted on non-human primates.

Have you checked the Science and Consciousness Review? I posted a link earlier in the thread. There are a lot of links to studies that have been conducted, although they're in online journals, so you have to pay to read most of them. If you are serious about learning more on this topic, though, it's worth it to purchase a subscription to journals that deal with the topic. You should have at least some working background knowledge of neuroscience as well.

You might want to check out these as well:

http://mitpress.mit.edu/catalog/item/default.asp?sid=09FC98E6-734F-4DD1-B623-57AADED5102C&ttype=4&tid=12

http://www.consciousness.arizona.edu/tucson/

Hypnagogue is going to the conference this year. If you have any questions about it, he's posted a thread in one of the philosophy forums (I don't remember which one) where you can ask him questions.

 

[Dissident Dan]

Thanks, loseyourname.

 

[zoobyshoe]

Big brains are expensive to operate. They cost a lot of energy. A better nose doesn't cost so much.

I just noticed this. An improvement in our sense of smell would actually require an inprovement in our smell processing centers. In other words, it would require more brain matter. Google "olfactory bulb" and see what you come up with. I'm pretty sure there is a correspondence between the size of this bulb and an animal's sense of smell.

Evolution, also, is not about getting better in any pure engineering sense. It is about those best adapted to the environment being healthier and better able to breed. The cognitive advantages of the energy-hog brain make it simpler and safer for us to take care of those extra energy needs than it is for many animals to do, whose brains need less energy. No species evolves toward any engineering improvements for the sake of nicer engineering.

We have excellent eyesight, sense of smell, and taste. We are also possessed of very fine tactile senses and excellent hearing. Our sense of balance and acceleration is quite fine. The fact that some other animals exceed us in one or more senses does not mean that our senses should be regarded as "poor". We are excellent runners. The fact some other animals can run faster does not make us "poor" runners.

With the incredible array of senses that humans have we are, indeed, able to sense very fine differences between one thing and another.

 

[spuriousmonkey]

Biology 101

There are extremely stupid animals (with hardly a brain worth mentioning) that can sense extremely well. That's right. It is not 'necessary' to have a big brain to sense very well. You may argue that it is, but nature shows that it isn't.

Therefore we have arrived at a point that you have a postulation and not a general correlation.


If it was really that easy (better sense of environment means better evolutionary fitness by means of a bigger brain) why didn't other animals follow the same path?

Who are the big brained animals in the animal kingdom?

1. Animals that live in a complex social group - big brain required for complex social interactions
2. Animals that lead an opportunistic life style - opportunity requires flexibility
3. Animals that prey on other animals - on average they often have bigger brains than their prey, but by no means this is always the case.

Humans probably can be put under all 3 categories in their early evolution.

 

[zoobyshoe]

Biology 101

There are extremely stupid animals (with hardly a brain worth mentioning) that can sense extremely well. That's right. It is not 'necessary' to have a big brain to sense very well. You may argue that it is, but nature shows that it isn't.

I am not arguing that it is. What I said was that improvement in our own sense of smell would require an enlargement of our own olfactory bulb, which is part of the brain.

Therefore we have arrived at a point that you have a postulation and not a general correlation.

I recall seeing comparisons of the size of different animal's olfactory bulbs. The point of these comparisons was to show that those with the larger olfactory bulbs had the better sense of smell. I never made the assertion that larger brains in general automatically leads to better senses. Better senses do, though, require that the part of the brain which governs a given sense be larger.

If it was really that easy (better sense of environment means better evolutionary fitness by means of a bigger brain) why didn't other animals follow the same path?

They have when having a better sense represented an advantage over others of their own kind. Consider a mouse born with an .02 % greater mass in its olfactory bulb than any mouse before it. This increase in neurons, let us stipulate, makes it far more sensitive to the smell of a certain kind of insect which the mice eat but which has such a faint aroma that they usually can't find them unless they're right on top of them. This mouse, with its increased ability to distinguish smells, can smell this insect at a distance of half a foot. It becomes fat and happy and breeds a lot of litters.

Note that your characterization of what I said: "(better sense of environment means better evolutionary fitness by means of a bigger brain)", is a mischaracterization. I am not asserting that a bigger brain, per se, is necessarily an advantage. It is only an advantage if it does something of use to the species that possesses it. I agree, though, with Ramachandrian that consciousness is differential phenomenon: we are conscious of the differences between things. His speculation that our own abilities to distinguish one thing from another was an advantage over earlier versions of our species makes perfect sense to me.

I am also not saying it is "that easy". I was singling this particular phenomenon out for observation in response to the original question. You somehow misconstrued me to be saying this is the only factor that is of any importance, which I wasn't.