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> Short-term and Long-term memory.
paros
post Feb 28, 2008, 12:14 PM
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STM = short term memory.
LTM = long term memory.


It seems me these days that there is a fundamental unanswered question sitting in the middle of all of neuroscience and cognitive science. It's sort of like an 800 lb gorilla in the room that noone is admitting is there. Even in the true research of artificial intelligence, this question is avoided with a kind of petrifying fear that thinking about it would hurt us in some way.

Anyway... this unanswered question is how LTM and STM relate to one another. Which one dominates the other? Is LTM a "repository" of memories like a hard drive, which the STM then "queries" for needed information which is returned to it like some sort of database? Or is STM like a slave of LTM, such that the STM is like the go-fetch dog whose responsibility is only to go grab data from the immediate environment by perception? Undoubtedly this relationship between LTM and STM is far more mysterious than anyone could have ever dreamed.

As scientists we admit to each other that there only exists the present moment of time. The past moments are already gone, and the future does not yet exist. Yet as a human being sitting at your computer reading this message you have a very convincing illusion that you exist within the "space" of an hour. Or that you are somehow "Straddling" a space between your past life and what you may do in the future years. This is all a very tricky illusion created by your powerful brain. But in the really-real world, you only ever exist in a perfect present moment. So now that you have realized that, and I have you in the basic conceptual frame that I need you to be, read the following facts:

1) You are perceiving now.
2) You are engaging in active behavior now.
3) You are thinking now. You are planning future behavior.
4) You are feeling emotion, now.

Perception, action, sensing, planning, feeling and thinking are all happening simultaneously. If not that, then some very powerful aspect of your brain is perfectly SCHEDULING them into little time slots best suited to giving you effective intelligent behavior.

Now lets move onto some even more troubling facts.

1) STM does not store anything in your brain. It does not place bits of info into "RAM" like in a computer. The way that it works is by creating signal feedback between cells in the prefrontal cortex and cells in regions of the limbic system, in particular the hypothalamus. As the minutes pass by this feedback becomes progressively weaker, which is why you cannot remember a phone number that you read an hour ago, even though you could repeat it easily after having read it.
2) The attentional focus is a behavioral (active) method of perception. Human consciousness cannot deal with every changing detail in a room full of people. This is why our focus will be in one place and not another. Children who come into a room will have their focus on particular things in that room. The adults will have their focus on something else. LTM has affected the very action of STM, in an autonomic manner. Because the adults have a larger history with the world, their focus goes automatically to those aspects of the room that are "concerning" or 'important" for adults. This example casts serious doubts on whether the STM is some sort of master over the LTM, and suggests that possibly the opposite is true.

Given that the STM does not store "data", this does not stop neuroscientists from still using erronious and mythological language when talking about LTM. They often say that the short-term memories are then "copied over" to the LTM which is stored in different locations of the cortex. What is copied? Some data? There is no data. STM is a feedback loop of signals. They then go on to use language that is even more peculiar. Saying that the STM then "retrieves" said memories out of the cortex, as if data is somehow stored there.

Of course, this theoretical paradigm of store-and-retrieve must have proper doubts cast on it. If you are presented with any problem in your life, there is an aspect of thinking about the problem using logic within an abstract framework of your STM. To what degree do you call upon your past wisdom in making sense of the problem? To what degree CAN YOU call upon the bulk of your entire life as it relates to the current situation? It's absurd to think that you may be retreiving each individual item of your LTM to compare and contrast. If that were the case, then it would take you hours to decide whether to have coffee with breakfast or not.

It does not take us hours to make decisions like that. LTM's action on our current behavior is immediate and effortless. One is almost led to believe that LTM is not "informing" our current behavior, but is SHAPING it. This again leads us to the idea that perhaps the purpose of the LTM is to shape the actions of the STM, whose only real job is work-a-day perception of the environment.

Researchers in robotics have found this problem so intellectually frightning that they avoid it by assuming, a priori, that their agents must schedule LTM and STM. It's amazing to me that actual scientists are doing intellectually dubious things like assuming something must be true because their own minds cannot come up with an alternative. The usual method here is to have their robot engage in a sense-think-act cycle, where each is done separately in its own scheduled timeslot. You want examples? Look at the DARPA grand challenge cars. This is precisely how they operate.

Indeed, in some respects the battle between LTM and STM has broken AI research down into two camps. Analogously, it has split neuroscience into two distinct camps who do not talk to each other. They are the Developmental Neuroscientists and the Cognitive Neuroscientists. (You know who you are.) This ever-growing rift between these two camps may have its roots in our inability to talk objectively about how wisdom and immediate logic fight against each other, or cooperate, as it were.
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Rick
post Feb 28, 2008, 02:57 PM
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Some interesting and original thoughts. It may be a bit more complex than LTM vs. STM.

Our attitude to the world (what interests us as we look around a room, for example) is a kind of habit that changes as we learn, so obviously, it's related to LTM. However, my attitude (as habit) is not constantly referencing LTM, it's a separate construct that is engaging the world. I suppose Freud would call it Ego.

I suppose the question should be "is my attitude to the world identical with LTM?" Maybe, but I seem to require distinct effort, separate from my "presence" in the now, at times to recall names, etc.

Also, as very much of our "in the now" attitude is unconscious, consciousness expanding substances may be useful in this research.
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paros
post Mar 01, 2008, 08:16 AM
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Thanks for your reply.

However, I am left dissappointed with this forum. I mean, thanks, but, that's it?
Pardon me if I appear rude, but one reply and no links to researchers or books or articles or pubs?

There must be better forums on the internet. Maybe I'm dreaming. Who knows.
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Rick
post Mar 03, 2008, 12:53 PM
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You'd think so, especially in the neuroscience forum. Maybe you'll get a better resopnse now that the weekend is over.
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paros
post Mar 07, 2008, 06:34 PM
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No. I don't think so. This forum is dead.

The internet is a wasteland.

Game over.
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maximus242
post Mar 07, 2008, 08:40 PM
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Well I think whats interesting about memory is how it affects us as conscious individuals. Think, I mean really think about what its like when you try to remember something and then ten seconds later are unable to recall it - to me, at the deepest level, this is very disturbing.

The reason why I find this disturbing is because it shows just how selective our minds are in what we do or do not retain. Of course being selective has enormous advantages as far as cognition is concerned. However, this also means that we do not absorb the reality around us, instead we selectively take pieces of that reality and construct our own.

Whats disturbing is that the finiteness of memory provides a perfect example of how distorted our views of the past are and of ourselves.

Ask yourself this, what if you woke up this morning, believing you were the person that you believe you are, with everyone around you also believing you are that person. But what if yesterday, you had the memories of a completely different person in a completely different place with different people supporting those memories.

Then you are in fact not one singular individual but a sum of the experiences you RETAIN instead of the experiences you have.

This is a very important difference. Thus we as in the self are not determined by the reality around us, but by the way we create our own reality and selectively choose which experiences to retain and which to discard.

It is a strange thought to think you could have been a completely different person, be given different memories and are now living a life of someone else's design. While it may seem outlandish, it is leads to many interesting questions.

Are we as individuals determined by the world around us or by the way in which we selectively choose the parts of the world to take in? If we as individuals are the sum total of our experiences and those experiences are not all retained by the memory - then we are the sum total of the experiences that we remember.

Thus memory defines the individual. I find this to be very important, since the mind is so selective about what it remembers and what it does not.

Another question that comes to mind is are we ever doing anything 'now' or are reacting to very recent memories? If you see a ball being thrown in your direction - by the time you perceive that ball, it has moved - if only a little. So then we use an extremely recent memory as a way of making a calculation for a future action, or rather reaction.

Then we use memory from how we have reacted to similar situations such as other objects being thrown at us and then search the memory for the reaction that lead to the most optimal solution. Which is, self-preservation in the most emotionally enjoyable way possible.

So perhaps we are never living 'now' in the sense of the word, but rather are moving in varying depth throughout the past - through the use of our memories.

As you read these words are you really reading them now or recalling albeit very vividly an extremely short term memory of a prior point when you read these words. Even if the difference is only a few fractions of a second, it has a very important impact on perception. Memories, as you should already know, are very unreliable in terms of accuracy. They are very easy to alter and the older they are, the more easily they can be modified.

So thus, if the past we know and remember is not really the past as it happened, what is it? We know we will recall events about today differently a month from now than if we recalled them today - especially if psychological suggestion were involved. So one has to ask the question, what are our memories really? I think maybe it is like looking into the past through stain glass, you don't get a clear picture of whats really behind the glass, just at best a blurry image.

Perhaps memories are like these blurry images. Strange to think that all of your memories are not really as they happened but are rather distorted versions of the reality you had experienced at a particular point in time. Very strange.
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