Do humans store every past experience since childbirth? I can remember bits and pieces of my life from when I was real young to now. I just can’t recall everything.
Is it still ALL in there? Does each memory has a certain trigger that activates it?
Thanks in advance for pondering this strange question!
WAG here: I’d say the brain’s memory doesn’t store every last little detail, but stores that which is important enough in short-term and long-term memory. So, you know how to ride a bicycle, you may remember the first lessons, but you don’t remember every journey and what was in each and every front yard you passed.
I’m not a neurologist and have no special expertise in this field, but I’ll tell you what I’ve read and (ahem) remember. There are two kinds of memories; short term and long term, and the long term is processed differently. There has been much research lately as to where in the brain it is stored, and I believe if memory (ahem) serves me right, it is like a hologram in the cortex; whereas, the short term is processed in the hippocampus. The fact (if it is a fact that I correctly recall, but I’m not at all sure) that long term memory is scattered throughout the cortex is the reason that association is the key to recalling things.
Now, if the event is of no particular importance or does not leave a “lasting impression,” the nerve pathways will not transmit the memory to the long-term storage, but will get no further than the hippocampus, wherein it fades quickly (the neurons either dieing or the signals being overriden). If it is memorable, your brain will further process the pathways into the long-term storage places, where you will be able to recall them, provided the proper nerve pathways are activated (by association, usually), or until you get old and senile and lose those neurons.
IANAN [I am not a neurologist] but it is my understanding that they believe memories are not stored in the brain like files on my hard drive but instead are stored as a matrix of connections between neurons distributed all around the brain. It is surmised that visual data pertinent to the memory is stored over here and olfactory data over there and emotional impression hither and temporal sequence charts yon and so forth.
IANAP [I am not a philosopher, at least not one who gets paid for it] but it makes sense to me that at any given moment when things are happening to you & around you, you make sense of the sensory impressions by comparing them to patterns you are familiar with. That is, you recognize this rectangular glowing thing with the black squiggly characters as
• an object of some sort sitting in front of you
• a computer monitor
• a computer monitor with some English text on it
• a monitor displaying a post from AHunter3 on SDMB
all of which require some degree of prior familiarity on your part or you would not be able to recognize them and remember them as such later, right?
Now hold a 7 hour old newborn up to the screen. Is she going to remember seeing a post from AHunter3 of the Straight Dope Message Board years from now? Of course not. She doesn’t know that’s what she’s seeing. She doesn’t know it’s a computer monitor. She hasn’t yet finished recognizing the pattern of events in her life that would lead her to conclude that this type of pattern of shapes and colors (and focal length) indicate an object sitting in front of her line of sight.
So what WILL she remember? Nothing that she’ll be able to recognize post hoc, for the same reason that if you stared at a piece of paper full of Sanskrit writing and THEN, years LATER, learned to read Sanskrit, you would not then be able to understand what had been written on the paper you once saw. Because memories are built up from correlations, from pattern recognition, and without the links to patterns of things you knew about at the time your brain has no real way of calling them up for you when you try to remember them.
IANRAKOE (I Am Nothing Resembling Any Kind Of Expert), but I’ll post anyway:
I can’t give a definitive answer, but I’ve been playing with some numbers that might offer a bit of perspective.
From an Annual Review of Neuroscience article we get a figure of approximately 100 billion neurons for the average human brain. Now, not all of those are used for memory storage (at least not exclusively), nor is the brain’s memory storage the same as digital computer storage, but let’s handwave a bit and see what happens.
Let’s pretend that each neuron acts as a bit. That gives us 100 billion bits of storage. One gigabyte is 8,589,934,592 bits. That gives us roughly 11.6 gig (or 11900 Mb) of storage. MPEG A/V files run somewhere in the vicinity of 6-7 Mb/minute, so we could store around 1830 minutes (30.5 hours/1.27 days) of MPEGs in that space. A 70 year lifespan, dropping 8 hours per day for sleep (assuming no long-term storage of dreams) would therefore require something on the order of 152 terabytes to store purely small-frame, low-res audiovisual memory. We would have to assume that the brain’s compression algorithm is more than 13,000 times as efficient to cram all that data in there. Even then, it leaves no room for kinesthetic, tactile, olfactory, or thought memory.
It seems reasonably certain to me that we don’t store everything–there just isn’t enough room in our skulls for it all. Our brains abstract the stuff that strikes them as important at the time and hangs onto it, but lets most of it go.
Of no little importance is the fact thata 7-hour child has not had complete brain development. Neurons are still being formed. I don’t know what age the brain reaches complete development, but I a WAG is at least two years.
I am no where near an expert in this area but I’ll try to explain what I learned in Psychology last semester.
There are three main types of memory: sensory, short-term, and long-term. Sensory memory is just held long enough for it to be processed further. An example of this would be when someone says something to you and you say “what,” but before they repeat themselves, you realize what they said. Short-term memories are just that, short. Anything in STM will only reamin there for up to about 15 seconds. However, if you recite that which you are trying to remember it will go into your LTM.
LTM relies on three things: encoding, storage, and retrieval. If all of these are done right, it forms a memory. Otherwise you forget it. If you encode the information right, that is, to take the information and change it around to something your brain can understand, you have it in STM. This forms the basic memory. The next step is storing it, or putting it into LTM. To remember a phone number you would repeat it several times to remember it. Once the information is in memory, it’s there, and it’s there for good. The last step is retrieval. If something went wrong with storage you will be unable to retrieve it.
My professor used to say, “you never unlearn anything, you just can’t remember it.” Of course there is much more to memory than what I have here. There are different types of memory and differnt ways of encoding, storing, and retrieving. Again, IANAP (psychologist) so I may have missed something here.
From The Developing Person Through The Life Span, Fifth Edition by Kathleen Berger…
A series of innovative experiments, notable in memory research, taught 3-month-olds to make a mobile move by kicking their legs (Rovee-Collier, 1987, 1990, 1999). The infants lay on their backs, in their own cribs, connected to a brightly colored mobile by means of a ribbon tied to one foot. Virtually all the infants began making some occasional kicks (as well as random arm movements and noise) and realized after a while that kicking made the mobile move. They then kicked more vigorously and often, sometimes laughing at their accomplishment. So far, this is no sxuprise-we know that such control of movement is highly reinforcing to infants. But would the infants remember this experience?
When some infants had the mobile-and-ribbon apparatus reinstalled in their cribs one week later, most started to kick immediately-indicating that they did remember. But when other infants were retested two weeks later, they did not kick any more than they had before they were hooked up to the mobile. Apparently they forgot what they had learned.
However, a further experiment demonstrated a remarkable effect: The infants could remember after two weeks if they were given a brief reminder session prior to the retesting (Rovee-Collier & Hayne, 1987)…
In this particular reminder session, 2 weeks after the intitial training the infants watched the mobile move but were not tied to the ribbon and were positioned so that they could not kick. The next day, when they were again connected to the mobile and positioned so that they could move their legs, they kicked as they had lerned to do two weeks earlier. In effect, their faded memory had been reactivated by watching the mobile move on the previous day.
Further research shows that the specific conditions of the reminder session can make remembering either easier or harder…
Carolyn Rovee-Collier, the lead researcher in this series of experiments, believes that natural reminder sessions are part of every infant’s daily experience, because the same events and circumstances occur day after day. Under the age of 6 months, infants recall only for a limited period of time, ony under specific conditions, and probably only events that include their own activities…
Nope, not every detail is stored. Some things likely aren’t stored at all–what did you have for breakfast five years three months and six days ago? There isn’t an emotional investment of meaning to it (probably), so there’s little long-term memory stored of it. If, however, you were eating waffles when you got a call saying your mom’s in the hospital (or something suitably jarring), you’re more likely to retain it. The “what were you doing when you heard JFK was shot?” routine.
It gets more complicated than that, though. There are explicit memories and implicit memories. Explicit ones are the ones we can consciously recall–“ah yes, that was the day when the big blizzard really hit. The missus and I were…” Implicit memories are stored in a different way. One of the famed case studies in neuroscience bits is a fellow who had a large portion of his hippocampus removed–he lost essentially all ability to form new long term memories. Short term worked fine–he could hold a conversation with some difficulty, etc, but walk out of his room and come back ten minutes later, he was seeing you for the first time. However, he could still slowly gain skills–tracing a figure, for instance, each day, though he had no memory of doing so, he still improved his performance of.
Explicit memory is a lot more fluid than many people are at all comfortable accepting. You know that “what were you doing on the day the Challenger exploded?” A study was referenced in Making Monsters, of just that. College freshman answered questions about who they were with, what they were doing, etc., on the Challenger explosion. And retested four years later. Their answers had almost all undergone some drift, and some a truly surprising amount. (This isn’t the kind of thing that would come as any kind of surprise to folks like police trying to reconstruct a crime scene from witness accounts.)
Doesn’t surprise me at all that babies forget things rapidly unless reinforced. IIRC, we’re born with a LOT more brain cells than we end up with at the age of, say, five. In the first year and especially months of life, massive amounts die off, all very according to physical plan. If that’s the case, the continual die-off is going to take memories down with it–least that sounds reasonable.
Thanks to all for your input!
Drastic,
Thats exactly what I was searching for, thanks. Couple questions though. Are you saying that Explict memories are like “repressed” memories?
My sister recently reminded me of a houseboat trip our family made together. (nothing to exciting) Once she described a few things we did on the trip, it all seem to come back me. I began to think about certain things I did beyond what my sisters was describing.
My point is that I would have never recalled that event without some type of memory stimulus. Was that memory gone for good, and somehow the mention of the trip by my sister created a “new” memory? Is my brain just filling bits and pieces of the trip because I know it DID happen, but the memories were gone?
My guess is that is the case.
Balance, nice handwave.
I second what AHunter3 said above about the information in a neural network being stored in the pattern of connections making it up. From what I understand, your consious thought process is a fluctuating pattern of neural firings. Any short term information is stored in this firing pattern.
When something is significant or important enough, the pattern is imprinted slightly on the entire network physically, making more probable to fall into that pattern again (remembering). As to when this happens and when it doesn’t, stuff we need to remember we usually do, and stuff we don’t, we forget.
As to childhood, considering the drastic changes being made to the structure of the brain during the first 9 years or so, it’s remarkable that we remember anything from the first three. What we do remember is very dream-like and relates mostly to the primal “child-like” corner of our mind.
It’s hard to tell which this was. Studies with respect to the phenomena of repressed memories have demonstrated that false memories can be implanted relatively easily in most people. Subjects in one study were reminded of an event in their childhood which did not occur and many claimed to recall it as an independant memory at a later date. Some recalled aspects of the event which were not told to them.
On the other hand we do sometimes lose things in the file system but can accurately recall details with prompting. The more connections to a piece of information the more likely you are to remember it.
Memories themselves are reconstructions, when I remember something that happened in my kitchen I am unlikely to be recalling the kitchen as it was that day. That would be incredibly inneficient. Instead, my memory reconstructs the scene with independant memories of the setting and specific recollections of the event. The more I do it the clearer the memory becomes but I have no way of knowing how accurate the visualization really is.
Years ago I witnessed an accident. I have a clear visual memory of passing one of the vehicles a block before it occured up to the impact. I doubt very much whether that visual memory is anything but a memory of the reconstruction that occured in my mind 15 or 20 minutes later after I had stopped, talked to them and given my name for use as a witness. I doubt my memory is accurate in respect of any aspect that I did not recognize as important at the time.
Everyone’s posts so far correlate with what I have read about conscious, retrievable memory.
However, what about “unconscious” memory? When I was younger, I’m pretty sure that I had read that one’s brain did indeed store “everything.” While not all memories were retrievable at will, memories could be retrieved by techniques such as hypnosis.
Has this been discredited?
Anecdote: in 9th grade, I flipped through all of the pages of a Latin dictionary, getting a good look at each page. I reasoned that my subconscious was “storing” this entire dictionary. Thinking back on it now, I think it was a waste of time.
BTW, Balance, I thought that the holographic nature of memory made it such that each neurons of the brain were able to store far more than one bit of information. The information , in fact was encoded in a certain pattern. As an analogy, our alphabet is composed of 26 letters. However, far more than 26 words are possible!
Nope.
Explicit simply meaning memories that are consciously recalled, searched for, sometimes aggravatingly hard to find. “What the heck was that phone number again? 1324? 1234? Hmmm…” The phone number of a friend, the title of that kickass book you read when you were ten and have been trying to recall for the last two years, the formula for the circumference of a circle, whose face that is, etc.
Implicit memories are more skill-based. Riding a bicycle, playing an instrument, touch-typing, the pattern of movements needed to get past that damn falling portcullis in Karateka (which I’ve forgotten), for example–conscious recall has little to do with anything; all of which isn’t really of the same sort of “stuff” as explicit memories above.
The explicit variety gets forgotten more easily–but I don’t think that means they’re lost, necessarily. Shifting networks of interconnectedness between neurons have something to do with long-term memory (whether or not it has the entirety to do with it, I don’t think anyone’s quite determined yet), as others have noted. Bits of those networked memories can get disconnected simply by lack of use–when you want to recite a poem by heart what do you do? Repeat, repeat, repeat–you’re strengthening whatever neural connections are there by repeatedly using them. But if you just read the poem once, then don’t think about it for years, that particular bit of network isn’t getting used, and more importantly, the connections to it aren’t. But maybe some years later, some stimulus happens, that trips a chain of memories that hooks up to the particular network that also encodes that poem, and it’ll come back to you. I doubt that’s anything to do with “repression”.
Also, complex memories of events are most likely to be stored in sort of skeletal form–not every little detail, but in broad strokes that are filled in by the process of remembering. “Then the dog ran under the apple tree chasing Fluffy…” The full details of that tree probably aren’t heavily stored, just sort of a pointer at the concept “apple tree”, which image of it in the memory is filled in based on experiences of apple trees in general. Details that stand out (the big sear mark from the lightning strike it survived, the tarred over stump of a branch that fell down in a windstorm the previous summer, whatnot) are used as hooks, that the rest of the memory are literally built in a narrative around–which seems to me the most likely explanation of why research is showing false memories are so (relatively) easy to implant in people under the right conditions.
[IANAP] (I am not a priest)
Even if the brain doesn’t remember everything, the soul does.
I saw this show on TLC or Discovery or one of those channels and the one thing that was consistant among all “near death” experiances was a “life review”.
Kinda scary, when I think about only the sh!t I CAN remember.
I’ve always had the theory that certain kinds of DREAMS are the result of memory house-cleaning.
The subconscious sucks up all the meaningless stuff and just spews it out in dreams. That’s why we don’t remember dreams either—we’re not supposed to.
There. I’ve said it and I’m glad!
True, many psychologists speculate that dreams are like the Recycle Bin on one’s computer. At night when dreaming, its like when one clicks the “Empty Recycle Bin” option. The memory reads the information, then pretty much erases it.
I’ve heard that, re the last two posts, and don’t believe it. For one thing, I do (and so do you) remember dreams you had before awakening, if the awakening is in the middle of the night. Moreover, I remember dreams I had when I did not awake right away. And I’ve had (and I’m sure you too) dreams with a recurrent theme.
Contrary to forgetting those memories, dreams reinforce them. You remember the dream and sometimes you can remember upon what it was based. For example, for many years I had a recurrent dream-theme, with slightly different facts, about not being able to take an el home, or sometimes a bus, or I just could not take any public transportation home. It wasn’t until I had that dream for many years and many times, it finally dawned on me that I tried to take an el home from downtown Chgo one night, but the Owl Service did not take me far enough. I’ve had similar dream patterns, which have stirred up old and “forgotten” memories.
Another citation from the same source as my previous post in this thread…
"…researchers are struck by the inaccuracy of memory in adults, even during the years when we think we remember best. For all people of all ages, memory is highly selelctive, sometimes false, and often self-serving; this may be more so the younger a person is (Loftus, 1997).
Moreover, just like the baby whose memory is aided by reminders, adults find their memories strengthened by reminders. The difference is that for children and adults, language provides significant assistance that babies do not receive (Schneider & Bjorklund, 1998). Reminders typically occur when we write or tell our memories to someone else; this gives our audience considerable power over what those memories will be. As one psychologist explains:
Our recollections are often elicited by and formed with other people. When this is the case, the past is created through narrative rather than being translated into narrative… Think back to some charged event in your own life-perhaps the first fight you had with your spouse. Now imagine telling that story to your mate, may years later at the celebration of your twenny-fifth wedding anniversary, telling it to your divorce lawyer, telling it to your children now that they are grown up, writing it in a humorous memoir of you now famous life, or telling it to your therapist. In each case the person you are telling it to, and the reasons you are telling it, will have a formative effect on the memory itself. (Engel, 1999).
At any age, the social aspects of memory are remarkable. Someone else’s memories and interpretations of an event can merge with our own; a single dramatic moment can be forgotten if others react neutrally but can be seared in our minds if others echo or exaggerate our own reaction. Just as with a baby, direct involvement, repetition, personal action, and emotional excitement make a memeory last longer…"
Deep stuff, that. I gather from the above that memory is greatly enhanced by brain maturation, language development, repetition, emotional context and one’s actual physical involvement during the episode that created the memory. The whole aspect of narrative also appears to have a significant effect on memory (think ‘recovered memories’).
Sadly I don’t have time to give a detailed comment here – ironically due to an overwhelming amount of studying to be done for psych finals! – but I can direct you to a page which contains several articles related to these areas of research. In particular, look for the articles by Elizabeth Loftus (very famous memory researcher) and by Amina Memon (who was incidentally a lecturer of mine this term).