When you go from bed to bathroom on a dark night, a quick flick of the lights will leave a lingering impression on your mind’s eye. For decades evidence suggested that such visual working memories—which, even in daylight, connect the dots to create a complete scene as the eyes dart around rapidly—fade gradually over the span of several seconds. But a clever new study reported in the journal Psychological Science finds that such memories actually stay sharp until they are suddenly lost.
Cognitive psychologists Weiwei Zhang and Stephen J. Luck, both at the University of California, Davis, tested subjects’ recall for the hues of colored squares flashed briefly on a screen up to 10 seconds earlier. Subjects marked their answer on a color wheel. If memories decay gradually, the guesses should have become increasingly imprecise as time wore on, evidenced by participants selecting yellow or red, for example, when the correct choice was orange. Instead subjects went straight from fairly accurate answers to random choices—no better than chance—indicating the memories were decaying all at once. According to Zhang and Luck’s mathematical analysis, most subjects’ memories went “poof” somewhere between four and 10 seconds after the stimulus.
Researchers say a sudden die-off is to be expected if working memories are stored in circuits that feed back on themselves. Luck says the system is like a laptop as compared with a flashlight. “The laptop is an active system that uses feedback circuits to limit how much power it draws,” he says. So whereas a flashlight dims when it runs low on juice, “the computer runs perfectly normally while the battery drains,” he says, “until suddenly the laptop shuts off.”
Note: This article was originally printed with the title, "Abruptly Forgotten."
This article was originally published with the title Abruptly Forgotten.
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24 Comments
Add CommentThat's a nice analogy to help the reader picture how our short term memory works but it rather thin. What acually happens? How does a feedback mechanism wipe the memory?
Reply | Report Abuse | Link to thisI can imagine a signal loop that turns itself off after it loops back on itself but I find it hard to imagine the loop taking up to 10 seconds.
I imagine that with no more incoming stimulus, the neurons responsible simply lose their plasticity. Since they work in a branching configuration; if the originator is no longer being exposed to the stimulus and shuts off, all connected neurons likely follow suit.
Reply | Report Abuse | Link to thisI worked with this in my mother's later years; she'd lost that connection between working memory and longterm.
Reply | Report Abuse | Link to thisBut while she would not remember something on TV or the radio or said in conversation easily, if she focused on a written note for a few minutes, she would remember that. We started by simply putting every question she had and every visitor's name and picture in a notebook, and insisting everyone cooperate.
Then we'd say 'it's in your notebook' if she repeated a question. After some days of going to the notebook, she'd start to ask a question, then say "Oh, it's in my notebook" and go look.
She would study that notebook seriously every day, and sure enough, after several minutes of sustained attention, she'd remember what was in there.
This gave her probably two extra happy years living at home, where she lived out her life til her heart failed; if this had not been done she'd have been dismissed as a confused old lady.
It takes real, serious work with people to get them to believe that working memory isn't working to write to longterm memory -- to convince them that anything said or seen is forgotten, but anything written down, and anything photographed, that can be studied will become a longterm memory.
I don't know how it is for other older people, but it's sure shaped my plans for getting older, knowing this worked out so well.
This makes perfect sense to me from the standpoint of evolution: we store information just long enough for it to be available if it is required for immediate safety. If it is needed, it is reinforced by the event that requires it. If it is not needed, it is quickly jettisoned to make room for short-term storage of newer information that may be more important, and the cycle repeats.
Reply | Report Abuse | Link to thisMy short term memory is much like your mom's was. Unless I remember to make a conscious effort to remember things these days, I simply won't. Every day I marvel more and more at how faithfully we have modeled the computer on human cognitive functions. There must either be a geographical area in the brain or a set of neurons dedicated by type which function in similar fashion to the RAM of a computer, i.e. like a slate which can be wiped clean or where new information displaces the old in FIFO fashion.
Reply | Report Abuse | Link to thisI am convinced however that the problem is not that short term memory fades more quickly as you get older. It is that recognition circuitry takes longer to click on than it used to. There is, for example, a perceptible lag between the time I fix my eyes on an object before me and my recognition of what it is I am looking at. This is probably because at sixty I have ten times more information to sift through than I did as a six year old, in order to find a matching template. I know that I my eyes have seen these objects because many times my hands react, to stop a falling object for example, before I even know what I am reacting to.
This means two things, firstly that you can react appropriately to a given stimulus before you consciously recognize it, which means that reaction is not dependent on conscious recognition, and secondly that it is therefore possible that recall is dependent not on response to a stimulus but recognition of that stimulus. So your mother was able to react and respond to events in her life quite appropriately; but unless she had more time to internalize what she was responding to she was not able to recall it for later use. Writing or even discussing any event gave her brain time to arrange the data in a way that allowed her to recall it more easily. (She just needed more time.)
My late wife used to tell me that she'd wake me from sleeping before the TV to get me to go to bed, during which time I'd carry on a perfectly normal and rational conversation. Next day my normally eidetic recall would fail completely, and I'd have absolutely no memory at all of being awakened or of having a conversation at all.
Reply | Report Abuse | Link to thisThe sequel to that came later when she was dying during which time for months on end I'd get by on 1 hour intervals of sleep at night and short naps sitting down during the day. That ended when my stepmother made a 3000 mile journey to help me with the nursing of my wife for several months. I had to be told about that because I have absolutely no recall of a 3 month visit during which I shared the apartment with my poor mom. The family thinks this memory loss is due to the trauma of my wife's illness. I on the other hand believe it is due to the fact that even after my stepmother came to visit I still had to awaken every hour or so to do the nursing.
I'm therefore advancing the suggestion that long term memory may have much to do with REM sleep, and the abrupt loss of short term memory may be natural but not as complete as the researchers seem to have concluded.
Short term memory requires recall and reinforcing by repetition,or seeing or imagining or notes to ensure that it is indelible in long-term memory. That is only natural since other wise we will lose much of our neural circuitry and energy in the brain reinforcing all the sensory inputs,which is not what nature has made us for.You need only remember what you should at the age and stage in life ,and there is no point in remembering all the muck that is better erased. Brain is trying to help us to keep our mind functional consistent with the natural demands on it based on some native intelligence,and not dancing to the tunes of some artificially imposed requirements or ego demands.Then of course there is the question of too much in storage ,as we advance in age which definitely detracts from the innate cpacity,and that is true with eye or ear,since as we age we retard in our functions,due to ebbing vitality and energy. The brain enhancers may work well for sometime and later on we may become mad just because we cannot forget certain things that are better forgotten at that age and stage of our life and energetics. It all boils down to conservation laws ,minimizing energy consumption,and conforming to a more natural state innately. We alter that by training or medicine at our peril,in due course ,since what we gain in short term memory thus may be compensated energetically as a loss in some other vital functionality,and that is how nature works. While balancing so many demands brain circuitry has to do some shut down servicing to keep alive more vital functions as the energy depletes.Pumping more energy and blood and nutrients for a tak to some parts will naturally mean shutting down some other part which is not currently in use but which may affect performance in certain areas of concern later on.So cognitive enhancers are definitely not the way out unless it is short term for some definite purpose
Reply | Report Abuse | Link to thisBest I can tell, there is no credible model of the way the brain encodes, recalls and uses memory. The model of the immaterial mind (a hopeless concept), blinds the ability to model a neuro chemical system that selects, catergorizes and assembles patterns that can be re-activated by associated current patterns into new current patterns to activate the neural muscle systems into appropriate activities which we will call intelligent thought and behaviour.
Reply | Report Abuse | Link to thisWe are amassing, huge amount of detail about how our assumed 'mind' model work in any regular way, but which casts no light on what a proper model might be. We have been analyzing ghosts in great detail to no great advantage.
The computer metaphor as applied to the brain does more harm than good; and plasticity isn't plastic enough to form connections from 0-4 seconds to then be completely forgotten in an instant somewhere between 4-10 seconds.
Reply | Report Abuse | Link to thisNew evidence is pointing to a phenomenon called Local Field Potential (LFP) to account for how a memory goes from pure energy (stimulation via any number of modalities; sight, sound, etc.) to the hard connections we erroneously compare to discrete computer logic.
It is far more likely that oscillations sustained by the coordinated firing are synchronized by LFP. This instantiates the complex coordinated behavior among many neurons, which is necessary to represent complex and integrated memories. Over time "hard connections" are formed if the LFP induced coordinating oscillations are maintained long enough to implement synaptic plasticity. If, however, plasticity does not have enough time to form (i.e. LTP) the more ephemeral coherent oscillation (i.e. STP) is lost in a flash as it collapses. All it takes is a few neurons in the temporarily coherent firing group to be "distracted" by other incoming stimulations. Memory takes sustained focus on a relatively stable pattern.
Computer feedback, which is digital and discrete, is fundamentally different than the feedback in the embodied brain, which is analog and distributed.
Think of this as more of an update of the previous file like when you save a new version of it.
Reply | Report Abuse | Link to thisThink of this as more of an update of the previous file like when you save a new version of it.
Reply | Report Abuse | Link to thisI had a perfectly great memory --in fact my job depended on that memory --then illness, seizures, a coma and other things hit. Both my short term and long-term memory were affected, so were word recall and spelling. I have used several tools to try to improve the functions, but can no longer work at what I do, it would be a legal risk. My short term memory does not even record much of a day --hours gone before I know it. It is not dementia. I have damage to the CNS from several sources (an undiagnosed genetic disorder) ---ammonia and now I think the poor innocent 3 day measles I had several times as a kid --HHV6. As I do more research on my brain and its functions to help myself it is amazing what is really not known. I am finding help with amino acid supplements as directed by a geneticist. We will see as time goes on. I do not want to be a burden to my family as my temporal lobes are bombarded. Amazingly my extremely high IQ has remained high in every area except math.
Reply | Report Abuse | Link to thisDid I ever tell you the story of my year in Arctic? It was 1968, I think then there was a great
Reply | Report Abuse | Link to thisWhile half asleep in a train commute on the way home after a night shift, I recently caught myself hearing the callout echo in my mind of the stop and the next stop in reverse order. The brain had already begun filtering to the equivalent of auditory dislexia, or perhaps a stack based short term memory in competition with a more queue-based conscious memory.
Reply | Report Abuse | Link to thishaving trauma memory problems i find a memory cut a while into study but using sub conscious memory tracking by cognate nomen in the sub or near conscious its full memory actant as clear as a bell and can be jogged by reading as it were to substantial recall
Reply | Report Abuse | Link to thiswhat seriously affects things is that time apparently wasted on textbook biblio therapy in a trauma locked brain can be calculated to fully enter appreciation modifying both behaviour and personality slaving seemingly vain efforts arent
Reply | Report Abuse | Link to thisI am now in my sixth decade of consuming alcohol regularly (the first 1.5 decades don't count) and I have always been interested in how alcohol affects the mind. I rather suspect that the main thing it changes in me is that if I have consumed a bottle or two of fine wine before bedtime it changes the way I sleep. Since I have sleep apnea I frequently awaken during the night with my dreams still vivid in my memory, which would indicate that I fall into REM sleep easily most nights and often right away, not having to wait until early morning to start dreaming. Perhaps the nightly alcohol has something to do with this.
Reply | Report Abuse | Link to thisAlso I should mention that there are tricks one can use to get by with the mental challenges of aging. For instance, feel your toothbrush to see if it is wet if you can't remember if you have brushed or not.
I do expect that the most accurate theory of mind will have to consider analog computers. My military service in the Vietnam years required me to have to work with a great number of analog gunfire control computers which were relics of my father's war, WWII. I found these machines to be absolutely fascinating, kind of like a combination of a Swiss watch and a slide rule (on which I learned to do engineering.)
One thing that has stuck with me was the clever way inputs could be merged linearly by having a chain fixed on one end and each input expressed through a movable pulle in two dimensions, the free end of the chain giving the output. Of course such systems inherently have "slop", which would produce distinct inidividual behaviors in human minds, but other parts of the system were quite quantized.
The most crucial factor causing deep or long lasting memories is the intensity of emotions that underlies an experience. Strong emotions leave an indelible mark. Also a seemingly transitory or casual experience or action that evokes emotional associations at conscious or subconscious level play a role in the encoding of memories.
Reply | Report Abuse | Link to thisMemory function is not a one dimensional phenomenon. Emotions, explicit or implicit, are integral facets of memories. Modern neurology has discovered that emotions play a very critical role in the functioning of intelligence, reason, thoughts and memory encoding. The well-known neurologists, Antonio Damasio has explained it in-depth in his book, The Feeling of What happens: Body and Making of Consciousness . One can also find a lucid discussion on this on the webpage: - http://rewiringthebrain.net/
Nilu
Yes, Michael Cook, REM sleep is linked to memory encoding, however non-rapid-eye-movement (NREM) sleep is believed to be even more important for optimizing brain energy and its functions including memory.
Reply | Report Abuse | Link to thisAccording to research, alcohol intake on a daily basis over years reduces neurons in the brain and thus erodes its efficiency. After intake of alcohol, body throws out double the amount of magnesium in the urine. Magnesium is very important for the functioning of heart and brain neurons.
Nilu
Yes, Michael Cook, REM sleep is linked to memory encoding, however non-rapid-eye-movement (NREM) sleep is believed to be even more important for optimizing brain energy and its functions including memory.
Reply | Report Abuse | Link to thisAccording to research, alcohol intake on a daily basis over years reduces neurons in the brain and thus erodes its efficiency. After intake of alcohol, body throws out double the amount of magnesium in the urine. Magnesium is very important for the functioning of heart and brain neurons.
Nilu
me cfs fms mcs has desroyed my short term memory have other surrers have this problem
Reply | Report Abuse | Link to thiscocnitive problems with me cfs fms mcs it has just taken me 5 times to join this site i just cannot match up passwords etc
Reply | Report Abuse | Link to thisWhile wondering at all the comments and learning from them as a novice, yet i remember some ages ago there was a theory that memory is stored as chemical molecules in the cells, betz? i frequently find that a point i wish to make, instantly disappears, as if the axon has lost contact with that molecule which has floated away. and later all of a sudden most of the times, not always, the contact is remade, and i get back the point clearly, as if nothing happened.
Reply | Report Abuse | Link to thisoh michael, i am 84m been in VN 1969-74 as a peace dr right at the fronts, consume alcohol one shot to one bottle a day,[funds], and the secret of the mind is to keep it engaged, reading writing and discussion,whatever, and DOING somefin w the hands and senses. and make your will and BE PREPARED for the journey beyond. the natural powers of the brain will see to alzheimers and parkinsons. lapses of memory are seen even in the very young and the growing, not only in senile me.
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