Hello, this be my first post, so hello everyone :)

I thought I'd just throw an idea in here that I find very puzzling.

Suppose scientists were able to create a human brain and keep it alive in a jar, without any other body parts attached. Just a brain. And the brain had not originally been in a living human's body either. Right from the start, it had been in a jar. What would this brain think? What would it feel?

Almost every thought I can have seems to be based on some sort of sensory information. If I think of a food, I am recalling the information picked up by the taste buds in my mouth. If I think of a friend, I am picturing her appearance, which I have seen with my eyes, or the things she has said, which I have heard through my ears. The brain in a jar could have none of these types of thoughts, as it would never have heard, never have smelt, never have seen, and so on.

So what types of thought do not depend on sensory information? Things like numbers I suppose. Although, when I think "four", I visualise the character "4" in my head, or the word, f-o-u-r. So even this I'm uncertain about.

What would it be like to be this brain?

Maybe nobody else finds this an interesting thought, but I find it mindboggling.

Just a thought, anyway ;)

I thought this might get moved. I was quite clueless where it belonged. Sorry! :)

I suppose that a brain that has received absolutely no imput is also totally devoid of thought. There is nothing to think about, no movement of body parts, no feelings, no information hence there would be no reaction to accomplish. The brain would just be without consciousness.

Furthermore, even numbers depend on an external input, you were not born with them in your head. Everything that your brain can think about was initiated by the enviroment, and to realize this enviroment you have to perceive it.

EDIT:
Welcome to sciforums. :)

Huuumm... maybe this should be on Human Science? :confused:

Anyways... thi sis an interesting thought.

Dreamwalker, with what you are saying, doesn't that imply that we depend on an external world to be conscious? :confused:
Is that a conclusion that we can draw from what you said? It certainly seem to be so.... :confused:

Yes, it does imply it. What do you think there would be to think about without any kind of reception? The brain would just be blank because there is no information with which thoughts can be constructed.

Like you said all thoughts come from sensory information. If no sensory information then the brain doesn't think.

I wonder if the brain would even be aware. You know, just aware it exists...

Probably there would be random sequences of perceived stimuli flashing through it. Your synapses are always active, and if you deprive your brain of sensory input for a period of time it will start making things up. (Sensory deprivation leads to hallucinations.)

Even neurons that have been ripped out of their normal network and grown in a dish will make synapses onto the other neurons in the dish and send action potentials back and forth. I doubt this activity is organized enough to produce anything resembling 'thought,' but nevertheless many neurons are quite active even in the absence of specialized input.

(Actually, many neurons in the brain - such as the output neurons of the globus pallidus and substantia nigra - are tonically active unless their firing is prevented by inhibitory inputs. A reduction in the normal tonic inhibition of pallidal and nigral neurons by the subthalamic nucleus can result in hemiballism: bizarre involuntary flinging and twisting movements in the unfortunate patient.)

I doubt this hypothetical brain in a jar would think about anything so structured as numbers; numbers are something you have to learn about from other people. Probably it would be more like flashing colors and meaningless sounds, smells, and other feelings.

You imply that the brain is being kept alive and functioning but do not suggest any input from external sources. Therefore, the brain functions on autonomous functionality only. There is no "thought"..................

Probably there would be random sequences of perceived stimuli flashing through it. Your synapses are always active, and if you deprive your brain of sensory input for a period of time it will start making things up. (Sensory deprivation leads to hallucinations.)

Even neurons that have been ripped out of their normal network and grown in a dish will make synapses onto the other neurons in the dish and send action potentials back and forth. I doubt this activity is organized enough to produce anything resembling 'thought,' but nevertheless many neurons are quite active even in the absence of specialized input.

(Actually, many neurons in the brain - such as the output neurons of the globus pallidus and substantia nigra - are tonically active unless their firing is prevented by inhibitory inputs. A reduction in the normal tonic inhibition of pallidal and nigral neurons by the subthalamic nucleus can result in hemiballism: bizarre involuntary flinging and twisting movements in the unfortunate patient.)

I doubt this hypothetical brain in a jar would think about anything so structured as numbers; numbers are something you have to learn about from other people. Probably it would be more like flashing colors and meaningless sounds, smells, and other feelings.

Thats about what I thought too... You put it in better words than I could have,

Probably there would be random sequences of perceived stimuli flashing through it. Your synapses are always active, and if you deprive your brain of sensory input for a period of time it will start making things up. (Sensory deprivation leads to hallucinations.)


is that not based on a brain that all ready has knowledge and images, the jar brain will have nothing to halucinate "on"... unless it creates its own envirement to escape the lack of input.

How would that happen? The brain would have no knowledge of any sort of world.

Well it could be a kind of dream state slowly expanding. Using colors to make it simple, maybe all the brain "sees" in the begening is red, then one day another color appears, maybe black and the brain thinks sweet multicolor and then on and on it goes. Hmm then sensory deprivations comes back to reinforce the dreamstate.

If that brain were linked in some way to another brain-in-a-jar, would they communicate? How complex would the link need to be before the two brains were effectively one?

Well.. to make it a bit more interesting.. what would happen to that brain in a jar if sensors are attached and it's a complex (let's say human) brain. How long could it be kept alive, i.e., what about decaying? Would that artificial consciousness (if it becomes one) could be kept active for hundreds of years?

? How complex would the link need to be before the two brains were effectively one?
Good question! I have no idea though, but multilinked brains is a very interesting idea. Sort of like a computer cluster. I think that it would have problems if they conflict, i.e., one brain has a visual input and the other has visual input, then those two imputs I think would conflict. However if one had only audio input and the other visual... I have no idea.