Splitting The Brain: What does this mean for the concepts of self and person?

[Fluffy]

A corpus callosotomy is a procedure in which the two hemispheres of the brain are disconnected from each other. People who undergo this experience split-brain where the functionality of various senses is reduced or altered due to the side of the brain that controls them and the inability to share this information between the halves. For example, a person showed an object in their left visual field would be unable to name it since this image would be sent to the right side of the brain whilst the speech centre is usually located in the left. They are not left mentally retarded,

A hemispherectomy is a procedure in which half of a person's brain is either entirely removed or disabled. People who undergo this are usually left mentally retarded but not always. Here is an in depth example case.

In the first scenario, a human is alive with two independent hemispheres in their head. These are not connected in anyway and cannot share information. Should we think of this human as 1 or 2 people?

In the second scenario, a person survives with 1 half of their brain. It therefore stands to reason that both halves should be able to survive independently of each other. If I could grow a body that did not have a brain, removed half of mine and placed it in its head, there would now be two alive humans who shared the same brain. Are these two separate people or are they the same person?

I think that these cases produce problems for the concept of self. When we think of self we think of a single being. If we reject any supernatural ideas such as the soul for a moment (although they also run into trouble) then the brain must be the source of this being since this is what creates this sense of self. How can we merge this with the fact that the brain can produce it without being unified or can produce it twice if we cut it in half? What is the difference between the person who has his brain separated in the same head and the person who has his brain in two different bodies?

 

[rocketman]

If I could grow a body that did not have a brain, removed half of mine and placed it in its head, there would now be two alive humans who shared the same brain.

But not the same brain stem. You can't really cut a brain completely in half and have it still work, even in a corpus callosum operation. And then, the two sides can eventually start talking to each other again through new pathway routings in the common brain stem in some cases.

What is the difference between the person who has his brain separated in the same head and the person who has his brain in two different bodies?

The brain stem.

 

[Fluffy]

Heya rocketman,
It is true that neither of these operations sever the brain stem. However, I don't see how the brain stem has sufficient functionality to produce the concept of self nor a personality. If we swapped brain stems, we would still be the same people.

Regardless, there is no reason why the brain stem cannot be split also although it would probably be more viable to replace it with individual organs that connect to specific processes.

 

[rocketman]

Heya rocketman,

Hey Fluffster. How's the Mother Country these days? (typical aussie small talk there, sorry).

It is true that neither of these operations sever the brain stem. However, I don't see how the brain stem has sufficient functionality to produce the concept of self nor a personality.

Question: Does a brain hemisphere work without a brain stem? Nope. Personality may derive wholly or partly from the hemispheres but nobody really knows where the deeper sense of self comes from yet.

If we swapped brain stems, we would still be the same people.

I doubt that very much.

Regardless, there is no reason why the brain stem cannot be split also although it would probably be more viable to replace it with individual organs that connect to specific processes.

I really don't think so. The brain stem is quite different to the dual design of the hemispheres. Here's a question for you: If you can take out either hemisphere and survive, how do you know it's not the brain stem that gives a sense of self?

edit: it's not just my idea Brain stem may be key to consciousness: | Science & Consciousness Review

 

[Fluffy]

Rocketman, I know very little about science and usually try and stay away from facts up in my lofty philosophers tower but occasionally these things strike me as having interesting implications for philosophical theories. Hopefully I will understand these facts better through debate but I apologise in advance if I get anything basic wrong.

Admittedly I am unsure of where we get our sense of self but I also realised that this is unnecessary for my purposes. I am less interested in our sense of self (i.e. our ability to identify our selves) and more interested in our definition of self (i.e. what we mean by self).

The two aren't linked. If I created a self-sensing machine and hooked it up to a being who had no sense of self there by enabling that being to sense itself so long as it remained connected then that being does not loose its "self" when I disconnect it. It only becomes unaware of its "self".

Therefore, there is no reason to think that the part of our body that gives us our sense of the self is the part which is actually our self.

The point is that there are plenty of parts of our body that we could lop off and still consider what remains to be our self. So all the parts we lop off cannot be part of our self. So what bit of our body is actually us? The bit that seems most central to us is the bit that defines us which is our brain or at least part of our brain which is where we are (largely) at before the possibility of splitting the brain.

When we identified that the self is in the brain somewhere, we took bits away until the brain was left. The brain cannot survive on its own, we'd need to create an artificial life support for it. However, most people agree that the body with a dead brain on life support is not a self whilst the brain in a vat is. Clearly the body can survive without the brain and equally clearly the brain can survive without the body. Therefore, it is not a question of survivability that determines where the self lies but how central the body part is in causing that self.

Looking next to dividing the brain, we can remove the brain stem and use the body as an incubator for the rest of the brain but controlled from an external system that replicates the brain stems functionality without being connected to the brain. The brain is then isolated from the world but otherwise continues to operate. We then divide the brain into two and each portion survives independently.

There are two options. Firstly, the self could be contained within the brain stem and so was lost when this was removed. This then means that the rest of the brain is not part of the self but the brain stem, lacking... well... everything does not appear to be anything in isolation. What does self mean if it is the brain stem? Secondly, the self could be contained within the cerebrum and so divided when the cerebrum is divided.

Also thanks for the site, it is very good! Adding it to my favourites .

 

[rocketman]

Rocketman, I know very little about science and usually try and stay away from facts up in my lofty philosophers tower but occasionally these things strike me as having interesting implications for philosophical theories. Hopefully I will understand these facts better through debate but I apologise in advance if I get anything basic wrong.

Don't get me wrong, I think the philosophical side of this is fascinating, and in a way I wish I wasn't hijacking this thread on philosophy with mere science ideas, which are far less interesting to me. I need to learn to stop questioning philosphers concepts and just accept them as that for the purposes of discussion.

Therefore, there is no reason to think that the part of our body that gives us our sense of the self is the part which is actually our self.

Well that's just it. Is "us" an effect that is generated as 'more than the sum of our parts' by the most sophisticated system we've ever known (brain) as many in the field think? Or is "us" some piece of tissue. When we think of our loved ones what do we think of? Do we think they are a piece of tissue only? I say there is something else going on.

Therefore, it is not a question of survivability that determines where the self lies but how central the body part is in causing that self.

Right, the minimal level of completeness of the system required to cause self.

What does self mean if it is the brain stem?

It could be the primal sense of self, as studies indicate. The more brain it is linked to, the greater it's state of being 'awake' or aware if you like. But surely if it is the root of the self, then the self cannot be seperated, only parts of the personality and processing can be alternatley blinkered off from each other ala corpus callosum?

Secondly, the self could be contained within the cerebrum and so divided when the cerebrum is divided.

If we could isolate the brain stem we would have a way of knowing if this were true or not.

But I apologise as I am veering this whole thing away from your original intent. So I ask, if the self could be divided into two distinct bodies, would their interactions be any different to that of twins, and why?

 

[Ozzie]

But not the same brain stem. You can't really cut a brain completely in half and have it still work, even in a corpus callosum operation. And then, the two sides can eventually start talking to each other again through new pathway routings in the common brain stem in some cases.

The brain stem

Right. And the cerebellum is not split either. The cerebellum is the site of storage of procedural knowledge (riding a bike)etc. It had the densest dentritic branching in the brain.