Brain Limitation

I read with fascination the dreams of immortality and have to laugh. I can think of a hundred reasons why we can never be physically immortal from the social (live long enough and you are bound to piss someone off enough who will kill you), the statisticical (live long enough and your odds on getting hit by a bus or by lightning approach 1), to the comological (Ain’t no one surviving the heat death of the universe). But then I realized another reason far closer in time, the brain. At some point the brain would be totally utilized. and so I wonder, what happens then? Do you lose the ability to learn? Does the brain begin to overwrite old memories and if so, is it random, chronological or from least accessed memories to most accessed? And are there any protected memories or could you actually wake up one day and not know who your parents were, or where you were born because those memories have been overwritten. Could the brain even begin to overwrite the areas where the body knows how to breathe, or speak, or see?

The things is the brain isn’t a computer, and it doesn’t work like one. Computers store information as a series of bits, literally as the presence or absence of information. Thus when a computer stores a memory of a face for example it literally memorises what parts of the face contained nose, and what parts didn’t, so a person with a large nose will simply have more information in the ‘nose’ part of the picture and less in the ‘cheek’ part pf the picture. That sort of processing works well for retaining very fine detail but it is hard to compress. It is also wasteful of space because in order to memorise a person the computer needs to memorise the face as a whole, the body as a whole, specific identifying markings at an appropriate level of detail. Then it needs to store different pictures of the person when happy, when sad and so on.

In contrast the human brain, as far as it is understood, stores information as reference information. So when a person starts life they memorise a specific face, presumably their mother’s. That initial memorisation is probably just as memory intensive as the way computer does it, relatively. But the efficiency of the brain is that every other face is stored as a reference to that. So Dad is stored as Mom with a narrower face and a beard, that’s all the information needed to distinguish those faces. Then Uncle Dave is Dad without a beard and with glasses. And the babysitter is Uncle Dave without the wrinkles, and with a longer nose. And that goes on throughout life.

The beauty of that system is that, in theory, the memory capacity of the brain is nearly infinite. Every new piece of information is referenced to previously memorized information, meaning that as the amount of information increases the amount needed for the next piece is reduced in proportion. The first face might take 10, 0000 ‘bits’, but the second face will only take 500 bits because it is just a header file referring to the first face and with a simple instruction to narrow the first face and add a beard. The next face might only take 100 bits because it’s just the first face + the second + instructions to subtract 20 years, and so forth. By the time a person knows 100 faces they can probably store the whole of humanity with header files saying “Person7s chin, person 8’s ears, person 179’s smile” and so forth. No new information is being stored per se, it is just a matter of cross-referencing existing information.

Now all those header and reference files will take up some space, so the brain will become full eventually, but it so over engineered that nobody has ever lived long enough to experience anything approaching it. People of 120 can still remember what their parents looked like, can draw pictures of their school and so on. Memories fade because of disuse, not because the brain runs out of memory capacity. As such it’s impossible to know what might happen if the brain ever reached capacity.

And no, the brain can’t overwrite areas where the body knows how to breathe, or speak. Those areas, especially the respiratory control centres, are the brain’s equivalent of ROM. They exist for a specific purpose and although they can be conditioned or temporarily overridden by the other brain centres they can’t actually be modified in the way your are talking about in adults.

Eep! We’re in GQ, so I’m just going to say that there’s really not much known about what happens when the brain runs out of room; similarly, we don’t know well how the brain stores much of any information at all. We know that there are, in a healthy adult human, centers or regions where particular types of information may be stored generally to the exclusion of other types of information. There’s little chance that having to learn a new word will overwrite your memory of Grandma.

Will it make you forget an older word? It’s likely you’ve forgotten words through disuse - name 14 dinosaurs. Could you do it when you were 7? This may very well be a bad example for you, but I’m sure you have a sense of what I’m trying to communicate. A new word could, hypothetically, take advantage of relics in the structure of your brain which used to hold words which you’ve forgotten through disuse. If you relearn the word allosaurus (if that’s a dinosaur’s name, and if you used to know it but forgot it, neither of which I’ll vouch for), it’d be easiest to relearn it by using the same combination of neural connections you used to learn it the first time.

What happens when you run out of room? No one’s ever done it. **Blake **is correct in that the oldest living humans don’t really show clear evidence that they’re overwriting old memories. The old memories aren’t as clear as they used to be, perhaps, and the new ones may not be as good either, recall is slower, learning time is increased, etc. But it really doesn’t appear that anything is ever erased or moved. There are neumerous problems with the normal neural degeneration that occurs with age, and those are problems we would be required to solve long before we put plans in motion to live to see the death of the universe. Estimating how difficult these challenges are relative to each other is a mostly pointless exercise.

Thanks, Blake, for the answer. It was concise and far better stated than even Cecil could pen. Every day I wake up and realize how much I don’t know. Maybe, if there is such a thing as nirvana it occurs when you wake up one day and realize you know nothing. I think some Eastern mystic said that sometime but I can’t remember who.

From the viewpoint of real, finite humans, the answer is perfect. It doesn’t answer my question, but does make it a hypothetical one. ASSUMING that humans could live for millions of years and ASSUMING that we have solved all the “little things” like the dozens of parts of the brain that breakdown over time, the brain would eventually run out of room. At that point, as when you send a BUFFER OVERFLOW to a computer, weird things happen. Is there any way of knowing if something similar could happen to the human brain? Is it really impossible that, at that extreme point, the brain couldn’t start overwriting areas of itself it wouldn’t normally overwrite? Even if the brain isn’t a computer it is still subject to acting bizarre under stress and certainly running out of room has got to be one of the ultimates in non-invasive stress. I know this is an academic exercise but unfortunately, my brain often needs answers to such “silly” questions and it is nice to know there is a place where it might get the answers. Be well.

No, there’s no way of knowing because nobody has ever approached that point.

AFAIK thebrina doesn’t really overwirte information as a computer might. The brain is a newtork of connections. Memeories are created as as reult of new connections forming, but also by the strengthening of existing conection. If apathway is used a lot it will become stronger in the sense of being more prone to activation. But there isn’t really any overwrite. There are short term memory connections that will simply fail to consolidtae, but they aren’t overwritten as such.

You might think of the brain as the road netwwork of a city. A snew suburbs are added new roadwasy are put in. Roads that get a lot of traffic are widened and so get still more traffic. Roads that get little use will get little maintainence and start to fall into disprepair making them slower to travel on, but the roads are never demolished. Short term memory is like unsealed temporary construction roads. They might only be used for a few days and then abaiondoned, and being unsealed they can revert to parkland or whetever but they are the only road type that gets ‘overwritten’.