Memory and Identity, Pt. 2

In regard to my previous post, “Memory and Identity“, Steven Den Beste asked:

In “Ghost in the Shell”, one of the technologies was cyber-replacements for sections of the brain. Even the guy who was “still human” had some of that.

If a part of the brain is replaced by a cybernetic equivalent, is that a break in continuity?

If eventually the entire thing is replaced, but incrementally, one small piece at a time, is there any discontinuity? (Presuming information copyover on each replacement step)

If the rest of the body is also then replace, one piece at a time, with mechanical replacements, was there any discontinuity?

At the end you have a creature which is entirely fabricated. Every bit of it came from a factory. Yet it has the memories of a biological being, and has exactly the continuity of identity you describe.

Is it the same individual? Does it really make sense to say that?

In a sense, this is happening already. Constantly, cells are dying and being replaced within our bodies. This fingernails that Steven hypothetically clipped are growing back as we speak, every bit a part of him, and yet every bit as much not his identity as ever before.

Supposedly, your body completely replaces itself every 11 years or so. That is to say that by the time eleven years have passed, every bit of physical matter in your body has passed out and been replaced. All the cells have died and been lost to waste, or sweat, or what have you, and all new cells have been created and are now running the show. (I’m going to guess, counter to the theory, that this does not apply to the skeleton.) Was there a break in continuity? Not by the standard of which we’re speaking. This is not akin to the “brain transplant” hypotheticals because it happened gradually rather than all at once.

First off, I can not imagine that any future technology that allowed us to replace parts of the brain could possibly be so crude as to resemble modern surgery. Doctors will not be able to go in with scalpels and swap out brain parts like an auto mechanic replacing a transmission — any such process involving such a delicate mechanism as the brain will probably more resemble giving a leukemia patient a bone marrow transplant, (in which the donated marrow is put into an IV feed and carried by the blood to the various parts of the body, and put into place by the body’s own natural processes).

In light of that, replacement of parts of the brain, while artificially induced, would still resemble the natural functions that are already at work within every human being. Our brains are being replaced, bit by bit, as we speak. In Steven’s example, the replacement would be of human design, and presumably more powerful than what nature gives us. This, still, does not seem to be too terribly different than what our brains already do — the structure changes hugely as we age, especially in the first ten or so years of our lives when our brain is literally wiring itself with neurons. (This is why it is easier for a child to learn music, or another language, than an adult — their brains are essentially pliable and are able to wire themselves to the type of information being input.)

I am not physically the same person I was when I was four years old, but… yes I am. I am not mentally the same person that I was at three, yet… I have memories of that age. Again, yes I am.

I’ve actually just thought of a different example that perhaps presents a more comparable situation which Steven suggests: Cryogenics. Cryogenics is the technical term for the freezing of a person’s body, usually after death in the hopes of reviving them sometime in the future when the technology exists to do so. I say “usually” because it is also, rarely, used on living people for the purpose of doing certain types of surgery such as… wait for it… brain surgery. One use for the technique is that they can eliminate blood pressure when doing reconstructive surgery on blood vessels in the brain. Freeze the person, pump the blood out, do the repair, put the blood back in, revive the person. Freaky but true.

If a person can be frozen to the point of cessation of body function, does this constitute a break in “continuity” as I have described it? On the immediate surface, I say “no”; it is more comparable to a deep coma. When the person is revived, the same processes (physical as well as mental) pick up where they left off. It’s similar to a person falling into freezing water in the winter and being pulled out an hour or two later, still alive (which happened several years ago here in Chicago). But again, what if instead of repairing blood vessels, the doctors are replacing the brain?

(Side Note: As far as Steven’s example above goes, I consider the replacement of the body parts irrelevant compared to the replacement of the brain. My arm is part of me, but it is not truly a part of what constitutes my personal identity. Though it might seem so, I would place such “identity-associated” body parts as the face in the same category as the arm. I have worn glasses since the second grade. Every time I get a new pair of glasses [new frames, that is] I go through a period where it is a bit of a surprise every time I look in a mirror; because glasses have become such an integral part of my physical appearance that to change them is to genuinely change the whole look of what I visually identify as “me”. In fact, I’ve had a few different people describe me as having “Clark Kent/Superman Syndrome”, meaning that if I take of my glasses I am hardly recognizable as the same person. Surely that difference does not actually make me a different person.)

What of replacing the brain while the patient is cryogenically frozen? I suppose that question depends on what part of the brain you replace. Swap out the motor centers, I would think that the consciousness is the same; but swap out the frontal lobes wholesale, and that would involve the kind of total disruption as whole-brain replacement, which I have already argued would constitute a continuity break.

“Yes”, I can already hear you saying, “but what about replacing just a small part of the frontal lobe, and doing that repeatedly over time until the whole thing is replaced?” Well, that’s a matter of degrees. We’ve already examined the two extremes — replacing it molecule-by-molecule in a way that mimics natural processes or replacing it wholesale like a mechanic swapping out spark plugs. Anything in between would be a matter of where you draw that line. Replace too much at once, and you disrupt the function enough to constitute a break; replace it in small enough bits and you are close enough to natural function to maintain continuity. I’m sure that there are areas in there that would resemble the kind of partial break similar to partial amnesia, or insanity, or brain damage, which have already been discussed.

3 Responses to “Memory and Identity, Pt. 2”

  1. Steven Den Beste Says:

    "Supposedly, your body completely replaces itself every 11 years or so."

    But that doesn’t mean all the cells have been replaced. Muscle cells and epithelial cells divide and grow and in their turn die, and most of the cells of our bodies are younger than we ourselves are.

    The most extreme case of that is the lining of the stomach, which is totally replaced every couple of days.

    The one big exception is nerve cells. Nerve cells stop dividing and growing at about age six months. At that point, each of us has all the nerve cells we’ll ever have. As we grow older, after that. some nerve cells die at a regular rate, but in most people it’s a very low rate and the cumulative loss doesn’t become significant even at age 80 or 90. We think and feel and control our bodies with the nerves which remain from age 6 months which have not yet died.

    The nerve cells which have died are not replaced. They’re just gone.

    The fact that nerve cells don’t continue dividing is the reason why there’s no such thing as "cancer of the nerves". (Brain tumors grow out of aberrant epithelial cells, not out of aberrant nerve cells.)

    Unfortunately, the fact that our nervous system is not replaced even once during our entire lifetime (let alone once every 11 years) would seem to undermine your argument a bit.

  2. Strider Says:

    I don’t thing it really undermines it at all. I already said that the "11 year rule" probably didn’t apply to the skeleton, but I don’t think that undermined it either.

    Right now, nerve damage is pretty much permanent. If, down the road, we invent some sort of artificial nerve replacement, it’s difficult to argue that a person having a damaged nerve replaced becomes a different person.

    Again, it’s a matter of scale. The point I was making is that the cast majority of your body’s physical tissue is being replaced naturally, and thus the suggestion that replacing the body piecemeal makes a different person does not necessarily hold water.

  3. Strider Says:

    Well, hell, Dan-o. I didn’t know you responded because for some reason this program forgot to send me an email announcing such!

    Brief response — The focus of the discussion was kept very deliberately narrow, because "personal identity" is such a massive topic that it’s far too easy to run off on a tangent, and never resolve anything — not that the question at hand is _resolved_, per se, but Like Den Beste, I prefer to take the massive issues and break them into managable parts, and then, by gum, try to manage them!

    "If most people you meet on the street have not overcome their genetics and the personality of their birth, then can we ever really have known them? Or did we merely get to know their genetics?"

    I suppose that if they haven’t moved past their own genetics, then their genetics are all they are. But I don’t actually believe that that’s true of anyone, except perhaps a mental vegetable.

    Regarding nerve regrowth — it is my understanding that nerves actually regrow naturally, on their own, but nerve _endings_ do not. If a nerve is severed in the middle, there’s hope of recovery. If a nerve ending is destroyed, I don’t believe any existing medical technology can recover that function.

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