Brain Transplant

Science & Technology Biosciences
1

Here’s an interesting thought experiment that I’ve been contemplating. I read somewhere that researchers were able to, or soon would be able to, create an artificial hypothalamus of a human brain. Let’s take this further, and suppose that one by one, a section of your brain was replaced with a artificial, yet fully functioning component complete with identical memories contained in the section of the brain being replaced.

Presumably after each operation where one section is replaced, you would still act, percieve, and think the same because the replacement parts exactly duplicated the function of the brain section being replaced.

Is there a point where you are no longer you?

2

To dispense with the convoluted example and get to the point, the question you ask is which aspect of our being is essential to our identity. To answer, we look for the property most important to our existence – our reasoning mind. The details of form and shape are irrelevant, so whether it is replaced by circuits in part or in whole, as long as it remains functional, our identity is unchanged.

By the way, the term “brain transplant” is wrong –since we identify ourselves by our minds rather than our bodies, the operation, if there were such a thing, should be called a “body transfer.” What you describe would be better called “brain reconstruction” or “overhaul”.

3

An interesting question - one raised by alot of SF writers and technology commentators such as Ray Kurzwell in “The Age of Spritiual Machines”.

In your question you did leave certain important aspects ambiguous -

Will the new brain parts be organic and therefore fit into our brains current biochemical system or will it be inorganic? If so I imagine the subjective experiance would vary greatly, to the point that certain aspects of your mind would be clearly different than others.

Will your attributes be enhanced? If I wake up with a new skill set and therefore on a different level than my former peers, can I say I am effectively a new person?

4

The details of form and shape are irrelevant, so whether it is replaced by circuits in part or in whole, as long as it remains functional, our identity is unchanged.

I used the ‘convoluted example’ for a reason. If you say this end result is still the same individual, then what if instead of reconstructing your brain piece by piece within your body, you simply built the whole thing at once inside of another body. And as in the original the 2nd brain would still be functionally the same as the original and contain all the same memories etc. Are there then two of you that are equally valid as you?

5

StarBuck, the new brain parts would be inorganic. But each piece would have identical function and abilities and stored memories as the original.

Will your attributes be enhanced? If I wake up with a new skill set and therefore on a different level than my former peers, can I say I am effectively a new person?

Your attributes would be the same. And as in the first example, you wake up after each piece is replaced. So if you think that at the end of the reconstruction you are a new person, at what point after you replace each piece are you a new person?

If you say no, you’re not a new person, look at the second example I wrote to GreedyCapitalist.

6

In “The Rediscovery of the Mind”, John Searle presents a similar thought experiment, and also gives some possibilities about what the results could be:

Imagine that your brain starts to deteriorate in such a way that you are slowly going blind. Imagine that the desperate doctors, anxious to alleviate your condition, try any method to restore your vision. As a last resort, they try plugging silicon chips into your visual cortex. Imagine that to your amazement and theirs, it turns out that the silicon chips restore your vision to its normal state. Now, imagine further that your brain, depressingly, continues to deteriorate and the doctors continue to implant more silicon chips. You can see where the thought experiment is going already: in the end, we imagine that your brain is entirely replaced by silicon chips. . . . In such a situation there would be various possibilities. One logical possibility, not to be excluded on any a priori grounds alone, is surely this: you continue to have all of the sorts of thoughts, experiences, memories, etc., that you had previously; the sequence of your mental life remains unaffected…

A second possibility . . .is this: as the silicon is progressively implanted into your dwindling brain, you find that the area of your conscious experience is shrinking, but that this shows no effect on your external behavior. You find, to your total amazement, that you are indeed losing control of your external behavior. . . . [You have become blind, but]you hear your voice saying in a way that is completely out of your control “I see a red object in front of me.” . . . It is important in these thought experiments that you should always think of it from the first-person point of view. Ask yourself, ‘What would it be like for me?’ and you will see that it is perfectly conceivable for you to imagine that your external behavior remains the same, but that your internal conscious thought processes gradually shrink to zero. From the outside, it seems to observers that you are doing just fine, but from the inside you are gradually dying.

[A third possibility is that] the progressive implantation of the silicon chips produces no change in your mental life, but you are progressively more and more unable to put your thoughts, feelings and intentions into action.

I dont think that theres any a priori reason to think that one thing is more likely to happen than another in this situation. Most people are going to have intuitons about what the result ‘must’ be, but I suspect that these are ultimately prejudices that are going to be incapable of rational defence. We just dont know enough about the workings of consciousness and the brain to say anything definite.

7

Wow… that is interesting that the idea was explored before. As I envisioned it, since each part of the brain that is replaced not only works the same, but has functionally identical interfaces to the rest of the brain that the original part had, it would seem to me that the 2nd and 3rd possibility could not happen.

I had originally thought of the idea when reading an article many years ago talking about the hope of immortality. When I read the article it was really about expert systems where a subject matter expert would teach a computer all he knew about a particular subject, or even everything he knew period. That’s not immortality to me. Even if it was more than just your knowledge that was stored, if it were an exact functional duplicate of your brain, yet in silicon form, sure it would think it was you, but the fact remains - YOU are going to die. So then I came up with the thought about replacing your brain piece by piece. It seems to me there would be no specific point where you could say you died. But on the other hand, I don’t see how it’s different than making an electronic brain that thinks and acts like it’s you but you die anyway. Interesting thought experiment though, I think.

8

One of my two biggest interests is brain research. And I also know a lot of things about how the brain works. I’d be happy to share my knowledge with you, to “brush it up” and to hear interesting questions, and also because this subject is so fascinating that I would simply enjoy telling about it and summing up what I know.

First of all, the operation that was suggested (replacing the brain by electronic devices, that would “store” the memories, so that the person would not feel the implant) is not possible. Our (and all animal’s consciousness) is expressed is changes is electrical fields of the cells in our brain called “neurons”. These neurons controls the behavior, movement, and a lot of things I’m sure nobody has a hard time thinking of.

The human brain contains about 100 billion (10^11) cells (neurons), which are organizes in specific regions in the cortex (which is the surface of the brain most close to the skull). The cells in the cortex recieve information from our senses, encoded in the frequency of action potential firing of the receptor cells.

“action potential” is a quick (1 milisecond) change in the voltage of a cell (which means that there is more positive charge inside the cell than outside it, in comparison to before the action potential). it is said that “action potential” is “fired” or that the cell “fires” because this action potential, once generated, advances through the axon of the cell, which is a long, thin wire, that is capable of causing the action potential to propegate until it reaches the end of the axon. the axon of each cell is connected to other cells, by a structure called “synapses”, through which the cells in our brain transmit information to one another.

if, in a certain instance, a neuron recieves enough inputs (action potentials in it’s synapses with other neurons) it fires an action potential of it’s own. here’s a great link that explains it: Action potential demonstration.

As I said, the rate of action potential firing encodes information. For example, if you’re looking at a dog then the cells in your brain that encode a shape of a dog, sound of a dog etc will start firing with higher frequency.

The connections between the cells can be replaced by an electronic device (though there is no such device today) and the consciousness of the person will not be harmed (his ability to learn will be harmed though, for reasons I will explain later), but the cells themselves cannot be replaced by an inorganic device without lost of consciousness. Our consciousness is composed of the neurons in our brain. For some reason, if you put a piece of metal that reacts just like your brain cells, it will be able to transmit information, but not to produce “thought” or “awareness”. We know that a rat that was implanted stem cells into it’s spinal cord with growth factors to encourage it to develope into brain cells, developed into brain cells and acted as normal brain cells do. There was actually no expiriment done which included replacing parts of the brain that produce awareness (not all the cells of the brain produce “consciouse” thought. some just calculate things and encode information we are NOT aware of) so I can’t be 100% sure about this…

However, with electronic “cells” we will loose our ability to learn, unless these cells will be a pretty good replicant of the original thing. The reason is that when we learn, what actually happens are chemical changes in a certain synapse that make it stronger (or make other synapses weaker). if the cell wont be able to respond with chemical changes to the stimuli it recieves from other cells, our brain will be incapable of learning. I’m going to post this now and continue later.

9

First of all, the operation that was suggested (replacing the brain by electronic devices, that would “store” the memories, so that the person would not feel the implant) is not possible.

Thanks Ifat, that was helpful. This issue has bothered me since High school. What innitiated it was ‘star trek’. When they beam or teleport, as I understand it, they take a dna picture of them, and recreate them from that map on the other side. Seems to me, that the ‘me’ on the other side as well as everyone he was familiar with would be fine with it, but I doubted that the original me would still exist which makes me a little uncomfortable. That is where I ran into a similiar problem. What if you were to replace a single atom of your brain? Would you still be you? We gain and loose cells everyday so it would seem unlikely that to replace a carbon atom, or even molecule should cause any change. what about a billion, or 50 billion?

It seems to me that on this level, you would be fine so long as you didn’t change locations and did it gradually so as to not upset the electrochemical balnce that we experience as conciousness. So Everything would need to be replaced piece by piece and allowed whatever time was necessary to be integrated within the confines of the system.

10

First of all, the DNA of your cells is not sufficient to make a perfect copy of yourself. The DNA can create a baby that is the same as the baby you were, but the genetic code does not store information about your current state (it doesnt hold information about how fat you are right now, the knowledge you have, the scars on your body etc). However, I do think that if someone created an exact replication of you, with your brain exactly as yours is, (but with different atoms) it would be you. The reason is that your identity is the different connections in your brain, the unique wiring and unique strength of connections between different cells in your brain. if you replicate that, even if you’d use different molecules, the product will undoubtably be you.

11

First of all, the DNA of your cells is not sufficient to make a perfect copy of yourself. The DNA can create a baby that is the same as the baby you were, but the genetic code does not store information about your current state (it doesnt hold information about how fat you are right now, the knowledge you have, the scars on your body etc). However, I do think that if someone created an exact replication of you, with your brain exactly as yours is, (but with different atoms) it would be you. The reason is that your identity is the different connections in your brain, the unique wiring and unique strength of connections between different cells in your brain. if you replicate that, even if you’d use different molecules, the product will undoubtably be you.

Sorry, I didn’t mean to imply that the DNA was the only picture required to rebuild. I am not aware of the details of “beaming” I assume since they appear intact on the other side, that it must take a complete picture including the state of their brain.

Do you mean you would be the same if you changed them atom by atom in the same location or if you teleported and were rebuilt somewhere else. My problem is with the transfer of conciousness. Because as was brought up earliar, if you could make an exact replica and not get rid of the old one, it seems like you would not simultaneously inhabit both bodies. I am unable to see how the original me would not cease to exist if it was ripped apart and a new one rebuilt somewhere else. It might be me as far as everyone else is concerned, but not so much for myself.

12

When they beam or teleport, as I understand it, they take a dna picture of them, and recreate them from that map on the other side.

I’m no trekkie, but I’m pretty sure “beaming” involves actually moving the constituent molecules to another location using a “carrier wave.”

13

I’m no trekkie, but I’m pretty sure “beaming” involves actually moving the constituent molecules to another location using a “carrier wave.”

Me either. That was how it was explained to me by a self described trekkie. I guess he and now I was misinformed. Even if they moved the actual pieces, I dont think that I’d be comfortable about the idea. Call me old fashioned, but I think that I’ll stick with the landing shuttle. :smiley:

14

Me either. That was how it was explained to me by a self described trekkie. I guess he and now I was misinformed. Even if they moved the actual pieces, I dont think that I’d be comfortable about the idea. Call me old fashioned, but I think that I’ll stick with the landing shuttle. :smiley:

If I remember right, one episode Riker(sp?) was beaming back through some sort of electrical field around a planet and the beam split forming a second duplicate Riker stuck on the planet. If it was moving the actual molecules in a wave, would this then just be a continuity error?

15

If I remember right, one episode Riker(sp?) was beaming back through some sort of electrical field around a planet and the beam split forming a second duplicate Riker stuck on the planet. If it was moving the actual molecules in a wave, would this then just be a continuity error?

That would seem to imply that there was more then molecule transfer going on. Any Trekkies on the site who can resolve this discrepency of their universe for us? :wink:

16

A brain transplant is the only transplant operation where it’s better to be the donor rather than the recipient.

:stuck_out_tongue:

17

If we could re-build our brains piece by piece, who manufactures those pieces? If we bought those pieces on credit and defaulted on our debt, would the debt collector own our brain?

Also, imagine if those brain-pieces were made by Intel or Microsoft, and then all of us needed an upgrade at the same time. That could be messy.

In all seriousness, I look forward to the days of mechanical brain implants. I would love a direct neural link to the web, bypassing something as inefficient as a keyboard. Is that possible?

18

Is that possible?

It contradicts none of my knowledge.

19

In all seriousness, I look forward to the days of mechanical brain implants. I would love a direct neural link to the web, bypassing something as inefficient as a keyboard. Is that possible?

Well in order to transfer information to the brain you need to physically plug something into your brain cells, because as far as it is known, all the perception, processing of information and awareness, is occurring in brain cells.

So the main problem you are facing, I guess (besides first understanding ‘neuron code’ for reason and concepts) is to plug the electrodes to the many many cells that process information of this kind: From what I’ve heard the brain tissue does not like electrodes inserted into it for a long period, and after a period of a few days the the micro-electrode gets covered with scar tissue and it stops being functional in delivering electric pulses, or receiving them.

20

So the main problem you are facing, I guess (besides first understanding ‘neuron code’ for reason and concepts) is to plug the electrodes to the many many cells that process information of this kind:

Done.