Why Memory Reactivation Cannot Explain Memories Lasting Decades

Neuroscientists typically claim that memories are stored in synapses, but this claim makes no sense. Very long-term memories cannot be stored in synapses, because synapses don't last long enough. Below is a quote from a scientific paper:

"A quantitative value has been attached to the synaptic turnover rate by Stettler et al (2006), who examined the appearance and disappearance of axonal boutons in the intact visual cortex in monkeys.. and found the turnover rate to be 7% per week which would give the average synapse a lifetime of a little over 3 months."

You can read Stettler's paper here. A 2019 paper documents a 16-day examination of synapses, finding "the dataset contained n = 320 stable synapses, n = 163 eliminated synapses and n = 134 formed synapses."  That's about a 33% disappearance rate over a course of 16 days, suggesting an average synapse lifetime of less than three months.

You can google for “synaptic turnover rate” for more information. We cannot believe that synapses can store-long memories for 50 years if synapses only have an average lifetime of about 3 months. The paper here says the half-life of synapses is "from days to months."

Synapses often protrude out of bump-like structures on dendrites called dendritic spines. But those spines have lifetimes of less than 2 years.  Dendritic spines last no more than about a month in the hippocampus, and less than two years in the cortex. This study found that dendritic spines in the hippocampus last for only about 30 days. This study found that dendritic spines in the hippocampus have a turnover of about 40% each 4 days. This 2002 study found that a subgroup of dendritic spines in the cortex of mice brains (the more long-lasting subgroup) have a half-life of only 120 days. A paper on dendritic spines in the neocortex says, "Spines that appear and persist are rare." While a 2009 paper tried to insinuate a link between dendritic spines and memory, its data showed how unstable dendritic spines are.  Speaking of dendritic spines in the cortex, the paper found that "most daily formed spines have an average lifetime of ~1.5 days and a small fraction have an average lifetime of ~1–2 months," and told us that the fraction of dendritic spines lasting for more than a year was less than 1 percent. A 2018 paper has a graph showing a 5-day "survival fraction" of only about 30% for dendritic spines in the cortex.  A 2014 paper found that only 3% of new spines in the cortex persist for more than 22 days. Speaking of dendritic spines, a 2007 paper says, "Most spines that appear in adult animals are transient, and the addition of stable spines and synapses is rare." A 2016 paper found a dendritic spine turnover rate in the neocortex of 4% every 2 days. A 2018 paper found only about 30% of new and existing dendritic spines in the cortex remaining after 16 days (Figure 4 in the paper). 

Furthermore, it is known that the proteins existing between the two knobs of the synapse (the very proteins involved in synapse strengthening) are very short-lived, having average lifetimes of no more than a few days. A graduate student studying memory states it like this:

"It’s long been thought that memories are maintained by the strengthening of synapses, but we know that the proteins involved in that strengthening are very unstable. They turn over on the scale of hours to, at most, a few days."

A scientific paper states the same thing:

"Experience-dependent behavioral memories can last a lifetime, whereas even a long-lived protein or mRNA molecule has a half-life of around 24 hrs. Thus, the constituent molecules that subserve the maintenance of a memory will have completely turned over, i.e. have been broken down and resynthesized, over the course of about 1 week."

The paper cited above also states this (page 6):

"The mutually opposing effects of LTP and LTD further add to the eventual disappearance of the memory maintained in the form of synaptic strengths. Successive events of LTP and LTD, occurring in diverse and unrelated contexts, counteract and overwrite each other and will, as time goes by, tend to obliterate old patterns of synaptic weights, covering them with layers of new ones. Once again, we are led to the conclusion that the pattern of synaptic strengths cannot be relied upon to preserve, for instance, childhood memories."

Research on the lifetime of synapse proteins is in the June 2018 paper “Local and global influences on protein turnover in neurons and glia.” The paper starts out by noting that one earlier 2010 study found that the average half-life of brain proteins was about 9 days, and that a 2013 study found that the average half-life of brain proteins was about 5 days. The study then notes in Figure 3 that the average half-life of a synapse protein is only about 5 days, and that all of the main types of brain proteins (such as nucleus, mitochondrion, etc.) have half-lives of 15 days or less.  The 2018 study here precisely measured the lifetimes of more than 3000 brain proteins from all over the brain, and found not a single one with a lifetime of more than 75 days (figure 2 shows the average protein lifetime was only 11 days). 

The paper here states, "Experiments indicate in absence of activity average life times ranging from minutes for immature synapses to two months for mature ones with large weights."

When you think about synapses, visualize the edge of a seashore. Just as writing in the sand is a completely unstable way to store information, long-term information cannot be held in synapses. The proteins in between the synapses are turning over very rapidly (lasting no longer than about a week), and the entire synapse is replaced every few months.

Well aware of some of the difficulties discussed above, neuroscientists sometimes speculate that maybe the idea of memory reactivation can explain how people can remember things for so long.  It is sometimes suggested that maybe a person can remember something for decades because he keeps reactivating the memory at periodic intervals, causing the old memory to be refreshed. So, for example:

• It might be that if an old man never thought of his first boyhood sweetheart, he might be unable to remember that person. But maybe every year that man thought of his boyhood sweetheart, causing the old memory to be periodically refreshed and reactivated. 
• It might be that if an old man never read again some fact he learned in high school such as the fact of Abraham Lincoln's assassination, he might have forgotten such a fact long ago. But maybe what happens is that every year the man reads some mention of Abraham Lincoln's assassination, which causes the old memory to become refreshed and reactivated. 
• An old man might remember the meaning of rarely-used words he learned as a boy, because he continues to speak those words occasionally or occasionally reads the words or hears the words, causing his memory of their meaning to become refreshed or reactivated. 

However, this reactivation theory does not work to explain the marvel of the lifelong preservation of memories. The fact is that even without memory reactivation, people can remember things for decades (as long as 50 or 60 years), even trivial things. I will now cite personal observations and experimental data which shows the truth of my claim in the previous sentence. 

A scientific study by Harry Bahrick was entitled “Semantic memory content in permastore: Fifty years of memory for Spanish learned in school.” It showed that “large portions of the originally acquired information remain accessible for over 50 years in spite of the fact the information is not used or rehearsed.” The same researcher tested a large number of subjects to find out how well they could recall the faces of high school classmates, and found very substantial recall even with a group that had graduated 47 years ago. Bahrick reported the following:

"Subjects are able to identify about 90% of the names and faces of the names of their classes at graduation. The visual information is retained virtually unimpaired for at least 35 years...Free-recall probability does not diminish over 50 yr for names of classmates assigned to one or more of the Relationship Categories A through F."

The scientific paper "Extremely long-term memory and familiarity after 12 years" documents an ability of some people to remember trivial sensory experiences after many years, experiences they should have forgotten under neural theories of human memory. In 2016 the study authors rounded up 25 subjects who had been briefly exposed to some very forgettable images in a scientific experiment done between eight and fourteen years earlier: thumbnail-sized images such as a little drawing of a coffee cup and a little drawing of a hen.  The subjects were tested with a set of images, half of which were the original images, and half of which were decoy images designed to be similar to the original images. The subjects were asked to guess whether or not they had seen the images before, when they were tested many years earlier. The authors expected the subjects to make guesses no more accurate than chance. But they found that the subjects were able to guess with about 55% accuracy.  We read this:

"In this study we found that our group of test participants was able to recognize simple colored pictures seen for a few seconds between eight and 14 years earlier. Our best performer, who had been exposed to the pictures at most three times, was able to identify 15 pictures more than the 84 pictures expected by chance. Note that no instruction to learn the stimuli was ever given to the subjects, even at initial encoding, which makes this performance even more remarkable." 

While researching tests of very long-term memory, I found a 1989 scientific paper ("On the Course of Forgetting in Very Long-Term Memory") on an interesting experiment that tested people by asking which of four titles was an actual title of a TV show. All of the actual TV shows were ones that only ran for one year. This is a good technique for testing very old memories never reactivated, because in the 1970's and 1980's in the US if a TV show ran for only one year it would almost never be shown in other years, and there would tend to be no references to it in popular culture. (This was before services such as Netflix, which might allow a program running only one year to be re-watched by many.)  Here is an example of some of the questions asked to the experiment's subjects:

1974

 Which of the following was a T.V. show? (a) Mandrake, (b) Shipmates (c) Private Nelson, (d) Lucas Tanner 

1978

 Which of the following was a T.V. show? (a) Gaslight Alley, (b) Cutting Corners (c) Black Knight, (d) Kaz 

1981

 Which of the following was a T.V. show? (a) Dateline Miami, (b) The Conductor (c) Discovery, (d) McClaine 's Law 

In these tests the tested subjects (231 in all) scored as shown below (25% is the result expected by chance, if no recall occurred).

We see here a good retention of trivial information that was learned between 7 and 15 years ago, with people scoring about 60% correctly, much higher than the 25% expected by chance. There would have been no reactivation of this trivial information. In the 1970's and 1980's if a TV series ran only one year, it was almost never mentioned again in the press, and would not appear on TV again. 

In my case in late August, 2025 not only did I recall that Lucas Tanner was an old TV show, but I also recalled the name of the show's star (David Hartman), and that the show was about a teacher.  At the time I had not watched this 1974-1975  show or read or heard any mention of this show in the past 50 years, nor had I ever thought about the show in the past 50 years. Similarly, in November 2025 I was watching a video about unsuccessful TV shows from the year 1974. There was a mention of the TV show "Get Christie Love," which was cancelled after a single year. I recalled that the star was Teresa Graves. Graves basically had no presence in TV or movies after 1975, and in 1983 retired from show business. At the time I recalled her name (November 2025), I had not watched this 1974-1975  show or read or heard any mention of this show or Graves in the past 50 years, nor had I ever thought about the show or Graves in the past 50 years.

In a similar vein, in the year 2025 I was watching a video on the most unpopular TV shows of 1973-1974. As soon as they mentioned the show The New Perry Mason, I remembered the star of the show was Monte Markham.  The show ran for only 15 episodes, and was never run in repeats after 1974, with there being virtually no mentions of it in the press since about that year. When the video mentioned  the TV show Adam's Rib without showing any of its actors, I remembered that it starred Blythe Danner and a tall blonde person named Ken, who played Thomas Jefferson in the movie 1776. I remembered both of their faces well. I was right about all of those details. The male actor's name was Ken Howard.  The TV show Adam's Rib ran for only 13 episodes, and never ran in repeats after 1974. When the same video mentioned the TV show Bob and Ted and Carol and Alice, I remembered that one of the stars was a short red-haired actress with the last name of Gillette. I was correct. The show ran for only 12 episodes in 1973, and never was seen after then. 

Similarly, while watching in 2025 one of these videos about the least popular TV shows from long ago, I saw a screen merely listing a title of It's About Time, a series that ran from 1966 to 1967, and was never syndicated after then. I correctly remembered that the show was about astronauts who traveled back in time into the Stone Age. I also remembered the melody and most of the first two lines of the show's theme song, remembering that it went like this: "It's about time, it's about space, __ __ __ __ __ __ __ place." In 2025 I had an equally good recollection of the melody and lyrics of the theme song of the 1965 TV series Hank, cancelled after a single season. 

Similarly, while watching in 2025 one of these videos about the least successful TV shows of 1970, there was mention of a show about young people in the American Revolutionary War. I instantly remembered the show was called "The Young Rebels." The show was canceled after 15 episodes. I am rather sure that there was never any reactivation of any memory involving the show, the show being basically unmentioned since 1970. 

In December 2025 I had a dream of Meredith MacCrae, in which she stated, "Mark, this is Meredith MacCrae." After awaking, I lay in bed trying to place the name. Soon I recalled that she had been in the 1960's TV show Petticoat Junction, one I had not watched in more than 50 years (and probably not heard mentioned substantively in more than 50 years). An internet search confirmed my recollection. I had not thought of Meredith in more than 50 years, and the press hardly mentioned her after the early 1970's. 

A test an old person can try is to remember some street names in cities or towns he lived in very long ago. Trying this test I correctly remembered the street name of a school that my children last attended 16 years ago, in a small town we moved away from 16 years ago. I had no sensory experiences refreshing the memory of this street name during the past 16 years, and I cannot recall ever thinking of the address in the past 16 years. Similarly, I remembered an avenue near my senior high school in a major city, an avenue with a name I have not remembered in about 50 years. 

So it simply is not true that to remember something for decades, you need  periodic reactivations every few years that recharge or reactivate a memory that won't last years without being strengthened.  You can learn trivial little things and remember them decades later, as much as 50 years later, even with no reactivations of the memory. 

An experience I had shortly before writing this post further showed this. Someone in my family had recently got a teapot, which caused me to recall the beginning of a children's song I had heard only a few times, only in a house I have not lived in for about 25 years. I remembered the first line: "I'm a little teapot, short and stout." I tried to remember the second line, but at first I could not. Later I remembered both of the first two lines of the song I had not heard or sung or remembered in about 25 years:

I'm a little teapot, short and stout

Here is my handle, here is my spout

In 2025 (as I noted at the end of the post here) I had a recollection which proved the ability of the mind to recall very old memories that have not been recalled in 50 years. For some reason I recalled a book I had read about 50 years ago, and never since: the science fiction book "Galaxies Like Grains of Sand" by Brian Aldiss. I remembered some lines from the book. I wrote them down on paper like this:

"The mirror of the past lies shattered. The fragments you hold in your hand."

After I wrote this recollection of something I had not read, thought of or heard quoted in fifty years, I borrowed the book on www.archive.org.  I see that the lines were these (almost exactly as I remembered them)

"The long mirror of the past is shattered...Only a few fragments are left, and these you hold in your hand." 

Below is a quote on the same topic from an earlier post discussing why brains cannot be the storage place of very old memories:

"I know for a fact that memories can persist for 50 years, without rehearsal. Recently I was trying to recall all kinds of details from my childhood, and recalled the names of persons I hadn't thought about for decades, as well as a Christmas incident I hadn't thought of for 50 years (I confirmed my recollection by asking my older brother about it). ...Upon looking through a list of old children shows from the 1960's, I saw the title 'Lippy the Lion and Hardy Har Har,' which ran from 1962 to 1963 (and was not syndicated in repeats, to the best of my knowledge). I then immediately sung part of the melody of the very catchy theme song, which I hadn't heard in 53 years. I then looked up a clip on a youtube.com, and verified that my recall was exactly correct."

One day in 2025 while lying in bed there strangely popped into my mind "out of nowhere" the name Toby Tyler, which I remembered was some circus movie I had seen as a child, in a theater. Looking up the name, I found it was the title of a circus movie that came out in 1960 (the title was Toby Tyler, or 10 Weeks With a Circus). I never saw the movie in a theater or on TV after 1960, and I never heard any mention of it on TV or in anything I ever read. Here we have an example of the remembering of a trivial memory from 65 years ago, a memory that was never reactivated after 1960. 

In late 2025 I was watching a Youtube.com video about the 10 least popular television shows of 1966.  I performed these wonders of memory recall relating to TV shows or TV personalities I have not seen or heard mentioned in about 60 years or more:

(1) Upon hearing the name of the 1966 TV show "Captain Nice" (canceled after a single season), I recalled its star was William Daniels. 

(2) Upon seeing an unlabeled photo of Judy Carne (an actress I have not seen on TV in 60 years and probably not heard mentioned in 60 years), I instantly identified her as Judy Carne. 

(3) Hearing mention of an "Occasional Wife" TV show I once watched in 1966, and seeing an unidentified image of its star, I first guessed the person's name as William Calley. Later (still having heard no mention of the star's name) I thought to myself something like, "No, I think it was maybe Michael Calley." The actor (who did no famous work after 1966) was named Michael Callen, a name identical to my final guess, except for a single character. 

Later I watched a YouTube video of the least popular TV shows of 1969. All of the shows mentioned were cancelled after one year or less, and none ever appeared in repeats after 1970. Hearing the name of the show "My World and Welcome To It," I remembered exactly the star was the obscure actor William Windom.  I also remembered that the main character's daughter would wear a noticeable orthodontic retainer.  The video soon confirmed that these 55-year-old memories were correct.  

In late 2025 I read an article claiming that the 1960's song "Yummy, Yummy, Yummy" was the worst song of the 1960's. Before playing a video of the song, I tried to recall the song, which I had not heard or recalled in more than 30 years. I successfully recalled the lyrics and melody of the first line of the song ("Yummy, yummy, yummy I got love in my tummy"), and also recalled the lyrics and melody of the song's middle refrain ("Ooh, love to hold you, ooh, love to kiss you"). 

While watching some of the 2026 Olympics with my daughters, I told them about how the show "The Wide, Wide of Sports" was a fixture of Saturday afternoon television during my youth. I remembered some words from the opening of this show which ran for many years, and ended in 1998, without ever running in repeats after that year. The words were: "Spanning the globe...the thrill of victory, the agony of defeat." I was quite certain that these were the exact words used in the opening of this show that I had not seen in 28 years. A search for the show's opening on Youtube.com showed my memory was correct: those were the exact words. I also remembered (before watching the YouTube clip) that at the moment the narrator mentioned "the agony of defeat" there was a clip of a skier tumbling. Watching the clip confirmed this visual memory was correct. These was a memory I had not thought about or mentioned in more than 28 years.  

I do not in general have memory good enough to be called photographic. But in May 2026 one of my daughters showed me a photo of a building with a rooftop lawn, and this triggered the memory of a book illustration I had seen 61 years ago. It was an artist's depiction of a base on Mars. In my memory I could see the illustration almost as if the book illustration lay before me. I sharply recalled the image of buildings underneath a glass dome, with the buildings having lawns on their roofs. I even correctly recalled the book's author (Arthur C. Clarke) and the book's title ("The Exploration of Space").  Checking on www.archive.org, I found the illustration was just exactly as I remembered it. You can see the illustration here. I may have looked at the book in a library years after seeing the book as a boy, but when I had this recollection I had not seen the book in at least about 40 years. 

Collectively all of these examples in this post show it is false that remembering something for decades requires periodic reactivations of the memory. Many people can remember trivial things for 30, 40 or 50 years, without any reactivations of the memory. Such abilities cannot be explained through any credible theory of brain activity, given the very high molecular turnover and synaptic turnover in the brain. 

Postscript: Another type of memory test is one in which you are shown photos you have never seen of TV actresses or actors well-known only decades ago, and asked to identify them, with the photo typically being from many decades ago, before the person became famous. Trying that with the video here, I successfully identified head portrait photos I had never seen of Jacelyn Smith and Angela Lansbury, taken from long before they became famous. I haven't watched either of these actresses on TV in several decades. Shown a photo of Sharon Gless from quite a few decades ago, before her first acting success, I identified her as the co-star of "Cagney and Lacey," even though the show was discontinued in 1989, and I almost never watched it and never saw it in repeats, and cannot remember seeing any other acting work of Gless. Trying the similar video here, and shown a head portrait photo I had never seen of Penny Marshall at about age 20, about a decade before she became famous, and with a different hair color than she had in her successful TV show "Laverne and Shirley" (1976 to 1983), I correctly identified it as a photo of Penny Marshall (someone I have never watched on TV in decades). Ditto for her co-star Cindy Marshall. 

Trying the similar video here, and shown a head portrait I had never seen of Stefanie Powers from years before her first acting success, I correctly identified her as Stefanie Powers, also identifying her first major role as the lead role in "The Girl from U.N,C.L,E" in the 1960's (the show ran only for one season), as well as identifying her second series ("Hart to Hart") which ran from 1979 to 1984. I also recognized a portrait of Rhea Perlman dating from about 14 years before her first acting success. I haven't seen her in anything for several decades. I performed a similar recognition (using a "way before she became famous" photo) of Isabel Sanford, identifying her as the lead actress in the TV show "The Jeffersons," a show I rarely watched, which stopped running in 1985. 

In May 2026 while brushing my teeth, I tried to remember cartoon characters I had seen as a boy. One of the characters was one I remembered as "Deputy Dawg." I tried to remember what the character looked like. I remembered four different features of his appearance: that he was a dog with floppy ears, that he wore a hat, that he wore a vest, and that on his vest was a sheriff's star (or police officer's star). Doing a visual image search, I confirmed that all four of my appearance recollections were correct. I had also correctly remembered the character's name, with its unusual misspelling.  The character of Deputy Dawg appeared in a cartoon TV series between 1959 and 1964, a series with an audience target of small children.  There were repeats up until 1972, but I never would have seen the character on TV after about 1967, around the time I started to stop watching all cartoon TV shows. To the best of my knowledge, I have never seen the character anywhere after 1970.  The ability of me to remember so well the character's name and appearance shows that memories can stay accurate for 50+ years, without any reactivations.  

Similarly, in 2026 I started to watch on youtube.com the opening credit sequence of the TV series Room 222, a series I had watched many times in my youth. The series ended in 1974, and I can never recall seeing it in repeats.  Before seeing the appearance of Karen Valentine in the opening credit sequence, I tried to remember what that looked like. I slowly and dimly remembered that the opening credit sequence showed her in a doorway, smiling broadly. My recollection of a sequence I had not seen in more than 50 years was correct. In the sequence she smiles broadly while standing for a moment in the entrance doorway of a bus. 

Similarly, in 2026 I saw a color TV scene (from the rather recent TV series Heroes) in which someone was holding a diamond. Very strangely this caused me to remember a black-and-white fictional TV scene I have not seen or thought of in more than 60 years, a scene in which Superman crushed a piece of coal to turn it into a diamond. A search on youtube.com confirmed that my recollection from 60+ years ago was correct. The scene is below. Clearly, memories never reactivated can persist for 60 years. 

In the year 2026 for some reason I decided to play on my computer a production of Donizetti's opera Lucia di Lammermoor on youtube.com. I had not watched any opera by Donizetti in decades. After hearing a few notes of the love duet at the end of Act I, I stopped the video and recalled the full melody, which I have not heard or "played in my mind" for many years. As it was playing, I tried to remember what I could recall about Donizetti. I recalled correctly that he was the composer of Don Pasquale, an opera I last listened to more than 35 years ago. I correctly recalled that he was the composer of an opera about a love potion, one including the often sung aria Una Furtiva Lacrima. I failed to remember the Italian name of the opera, (L'Elisir d'Amore) but did correctly remember the English name of the opera (The Love Potion). I correctly recalled that the opera (which I had not seen or thought about in decades) had a scene in which a shady salesman (with a name beginning with "Dul") arrived in a kind of covered wagon. I recalled some elements of the plot. I also recalled a conversation I had more than 38 years ago with a woman I met on only one day, with the topic being the love potion opera by Donizetti. I also recalled a soprano I had once met more than 38 years ago, who said that the title role of Lucia di Lammermoor was one of her strongest roles. These were mostly accurate recollections of things I had not thought about or remembered for decades, and things I had not been reminded of in decades. 

I find Yahoo.com to be a great easy-to-navigate site that is great for keeping up with the world. It has a vertical stack of about 25 stories a day that is very easy to traverse. It seems almost every day I get a "teaser headline" about some old song that came out in the 1960's or 1970's. The "teaser headlines" never mention the song's name, but just give you some interesting-sounding phrase designed to make you click on the headline to go the story. You might call this "musical nostalgia clickbait." It is amazing how often an old person like me is able to remember the lyrics of the songs I have not heard in decades. For example, one recent article was about the song "Delta Dawn," and told us that Helen Reddy recorded it when she had only 12 dollars to her name, with the song then becoming a #1 hit. Before looking up the lyrics, I wrote down to the best of my recollection the lyrics of a song I have not heard or recalled or thought about or read about for at least 30 years, writing down this:

Delta Dawn, what's that flower you have on?

Could it be a faded rose from days gone by?

And did I hear you say, he was gonna meet you here today,

To take you to his mansion in the sky? 

My recollection was perfect, except for the minor glitch that the line was actually "a meetin' you here" rather than "gonna meet."

Seeing an online trivia quiz about the friends of the TV purple dinosaur character Barney, one offering four plausible-sounding pairs of names, I was very confident that the correct answer was "BJ and Baby Bop," even though I had not watched the show for more than 20 years. I was correct, and correctly recalled the two colors of these figures (yellow and green). In a later trial my daughter correctly identified  "BJ and Baby Bop" as being the right answers (from a list of six plausible-sounding names I offered), and also correctly identified the colors of the characters. I am pretty sure she had not watched the show in more than 20 years, because once a child becomes about 10, it becomes utterly "uncool" to ever watch the Barney show designed for young children. 

In 2026 I saw only the title of a youtube.com video on the topic of Avalon Hill military board games. I had not read anything about military board games in almost 50 years, and had not played any military board games in almost 50 years. Before watching the video, I tried to remember what Avalon Hill board games I had played in the mid-1970's. I correctly remembered the title of one such game: a title of Panzer Leader. I also remembered that about this time a highly ranked game had a title of Drang Nach Osten, and that it was about the German invasion of the Soviet Union. I had never played the game, and I am 99% sure I had never heard the game mentioned (and never thought of it or spoken of it)  in more than 45 years. A web search confirmed my recollection was correct. 

Trying to Explain Memory, a Neuroscientist Gives Us Bad Descriptions and Vague Circuitous Hand-Waving

A recent NPR interview offers us an example of how empty-handed today's neuroscientists are when it comes to explaining how a brain could produce effects related to memory. You can read a transcript of the interview here. An interviewer announces that the subject will be "Why Do We Remember?" We are told that the person will be a cognitive neuroscientist specializing in memory, who has been researching memory for 25 years.  The person is Charan Ranganath who "directs the Dynamic Memory Lab at the University of California, Davis, where he's a professor of psychology and neuroscience." He has written a book called "Why We Remember."

I can understand why a neuroscientist writing a book on memory might pick a title such as "Why We Remember" rather than a title such as "How We Remember." The reason is that no neuroscientist has any credible detailed theory as to how a brain can produce any of the main phenomena of memory.  No neuroscientist can credibly explain how a brain could ever store information such as the information you learn in a school lesson.  No neuroscientist can credibly explain how a memory could persist for decades in a brain subject to such very rapid turnover of protein molecules, and subject to such constant remodeling of things like synapses and dendritic spines, which do not last for years.  No neuroscientist can credibly explain how a memory of something experienced long ago or learned long ago could ever be instantly retrieved by a brain, which has none of the things humans put in devices they manufacture to allow instant information retrieval (things like addresses, indexing and sorting).  So lacking any credible tale to tell of "how we remember," a neuroscientist might want instead to change the subject to "why we remember." 

But switching the subject to "why we remember" is a pretty futile task for any materialist, because so very much of human memory makes no sense from any kind of evolutionary standpoint.  For example, the history of musical achievement is full of cases of people who can play or sing many thousands of notes from memory (such as pianists who can play from memory all of the piano notes in a long piano concerto, or opera singers who can sing from memory long roles requiring the correct retrieval of thousands of notes, and also corresponding words). Why would anyone have such an ability, which has no survival value in the wild? And there are also many people who have memorized very long bodies of text such as the entire Quran or the entire text of an epic poem such as the Illiad or Paradise Lost ( retired teacher John Basinger memorized all 60,000 words of Paradise Lost). Why would anyone have such an ability, which has no survival value in the wild?

In the long interview on the topic of memory, neuroscientist Ranganath says scarcely a word about the brain. What he says about the brain is sometimes wrong. He states this:

"So the human brain is much more like the high-efficiency but also high-performance sports car. We're not designed to carry tons and tons of junk with us. And like you said, I don't know that anyone would want to remember every temporary password that they've ever had. So I think what it's designed for is to carry what we need and to deploy it rapidly when we need it."

The analogy is an extremely misleading one, because brains do not have any moving parts, and cars do have moving parts, such as the wheels and the steering wheel.  And by saying "we're not designed to carry tons and tons of junk with us"  and that we're designed to "to carry what we need," he is misspeaking very badly.  The average human can remember endless thousands of details about things he experienced in the past,  songs he heard, TV shows and movies he watched,  and a huge variety of things he does not need to know.  And humans can do things like memorizing hundreds of pages of text and memorizing many very long opera roles (as Placido Domingo did), and very long roles such as the role of Hamlet. It is not at all true that human memory merely "carries what we need."

Neuroscientists commit this type of error very frequently. They speak as if their ideas about how humans mind performed were derived from their dogmas about a neural basis of the mind, rather than from a thorough study of the best performances of human minds. 

Later we have more bad misstatements from Ranganath. He states this:

"Stress makes it harder to pull out the information you need when you need it. It basically kind of shuts down the prefrontal cortex."

No, it is in general not true that under stress a person's memory freezes up. When you watch the TV show Jeopardy, you see people under stress performing memory recall with lightning-fast speed. And every person who does well on a final exam at college is doing memory retrieval  very well under a stressful situation. There is zero evidence that the prefrontal cortex ever shuts down during conscious experience, except in the cases of near-death experiences, where people may have the most vivid and memorable experiences when the entire brain has shut down during cardiac arrest.  To the contrary, the neurons of the brain keep firing at a rate between about 1 and 100 times per second, during both normal waking consciousness and sleep. 

Ranganath then tries to make it sound like he has some understanding that stress damages memory. He states this:

"Then there's the issue of chronic stress, where we know that chronic stress can be actually neurotoxic for areas of the brain that are important for memory, like the prefrontal cortex and another area called the hippocampus. And that is really, I think, part of the problem that you see in people with PTSD, for instance."

PTSD or post-traumatic stress syndrome is a problem when people are disturbed or distressed by memories of traumatic experiences they had. PTSD is not some difficulty in remembering, as Ranganath has insinuated. Quite the opposite, PTSD is when people are distressed by unpleasant things they remember all too well.  

Later Ranganath gives us some nonsense trying to suggest that our memories are being devastated by the use of social media. He states this: 

"So there's a platform called Snapchat where the information literally disappears within, I don't know, 24 or 48 hours. And I think that's a metaphor for how technology can impact our memories in general."

No, actually, social media has not done anything to worsen people's memories.  Later we have more falsehood and nonsense from Ranganath when he says this:

"Those memories are being transformed little by little because the act of recalling them and sharing them changes it. So you tell me a memory, and it's no longer your memory. It's our memory because of the work that we put into in terms of transforming it."

No, actually when I tell you my memory of something, that memory of mine is not transformed; and it still is my memory. Later Ranganath repeats the unfounded neuroscientist legend that sleep does something to strengthen memories, an idea that is not well-supported by evidence. It is merely true that someone sleep-deprived might find it harder to learn as well as when he is sleeping normally.  He approvingly quotes some person saying the not-very-credible idea that sleep converts memory into wisdom.  

Ranganath sounds quite confused about memory in this interview.  He gives us no sign that he understands any neural basis for human memory. There is no such basis. No one has ever found the slightest speck of something someone learned by microscopically examining the tissue of that person's brain. Brains have not the slightest resemblance to a device for storing learned information, and not the slightest  resemblance to a device for instantly retrieving learned information or retrieving learned information at any speed. Memory is a spiritual or psychic or soul ability, not a brain ability. 

Postscript: I recently got further evidence of how false was Ranganath's claim below, suggesting people don't remember lots of old memories they don't need to remember:

"We're not designed to carry tons and tons of junk with us. And like you said, I don't know that anyone would want to remember every temporary password that they've ever had. So I think what it's designed for is to carry what we need and to deploy it rapidly when we need it."

I was watching a Youtube video about the 10 least popular television shows of 1966.  I performed these feats of memory recall relating to TV shows or TV personalities I have not seen or heard mentioned in about 60 years or more:

(1) Upon hearing the name of the 1966 TV show "Captain Nice" (canceled after a single season), I recalled its star was William Daniels. 

(2) Upon seeing an unlabeled photo of Judy Carne (an actress I have not seen on TV or heard mentioned in about 60 years), I instantly identified her as Judy Carne. 

(3) Hearing mention of an "Occasional Wife" TV show I once watched in 1966, and seeing an unidentified image of its star, I first guessed the person's name as William Calley. Later (still having heard no mention of the star's name) I thought to myself something like, "No, I think it was maybe Michael Calley." The actor (who did no famous work after 1966) was named Michael Callan, a name identical to my final guess, except for the last syllable. 

(4) The next night I had a dream of some office worker I had not spoken to or substantially thought of in 37 years. At first I failed to recall the name of this person I would only briefly see on any day, but soon correctly recalled his full name. 

The fact is that humans my age can recall all kinds of obscure useless memories from 50 or 60 years ago, memories never reactivated during such a period. There is no credible neural or evolutionary explanation for such an ability.  If your brain stored memories, you would not be able to remember any old memory you had not used for more than a year, because of the very high molecular and component turnover in brains. The proteins that make up synapses have an average lifetime of only a few weeks or less.