How
is it that humans can remember things for decades? For decades
neuroscientists have been offering an answer: that memories are
stored when synapses are strengthened. But this idea has never made
any sense. There are two gigantic reasons why it cannot be correct.
The
first reason has to do with how long humans can remember things.
People in their sixties or seventies can reliably remember things
that they saw 50 or more years ago, even if nothing happened to
refresh those memories in the intervening years. I have a long file
where I have noted many cases when I remember very clearly things I
haven't thought about, seen or heard about in four or five decades,
memories that no sensory experiences or thoughts ever refreshed. I
have checked the accuracy of very many of these memories by using
resources such as Google and Youtube.com (where all kinds of clips
from the 1960's TV shows and commercials are preserved). A recent
example was when I remembered a distinctive characteristic of the
“Clutch Cargo” animated TV show (circa 1960) that I haven't
watched or thought about in 50 years, merely after seeing a picture
of Clutch Cargo's head. The characteristic I remembered was the
incredibly poor animation, in which only the mouths moved. Using
youtube.com, I confirmed that my 50-year old recollection was
correct. A scientific study by Bahrick 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.”
Is
this reality that people can remember things for 50 years compatible
with the idea that memories are stored by a strengthening of
synapses? Synapse strengthening occurs when proteins are added to a
synapse, just as muscles are strengthened when additional proteins
are added to a muscle. But we know that the proteins in synapses are
very short-lived. The average lifetime of a synapse protein is less
than a week. But humans can reliably remember things for 50 years,
even information they haven't reviewed in decades. Remarkably, the
length of time that people can reliably remember things is more than
1000 times longer than the average lifetime of a synapse protein.
The
latest and greatest research on the lifetime of synapse proteins is
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 less than
20 days.
Consequently,
it is absurd to maintain that long-term memory results from synapse
strengthening. If synapse strengthening were the mechanism of memory
storage, we wouldn't be able to remember things for more than a few
weeks. We can compare the synapse to the wet sand at the edge of a
seashore, which is an area where words can be written for a few
hours, but where long term storage of information is impossible.
It
may be noted that scientists have absolutely not discovered any
effect by which synapses undergo any type of strengthening lasting
years. Every single type of synapse strengthening ever observed is
always a short-term effect not lasting for years.
There
is another equally gigantic reason why it is absurd to maintain that
memories are stored through synapse strengthening. The reason is
that it is, in general, wrong to try to explain information storage by
appealing to a mere process of strengthening. Strengthening is not
storage. We know of many ways in which information can be stored, and
none of them are cases of strengthening.
Below
are some examples:
- People can store information by writing using a paper and pen. This does not involve strengthening.
- People can store information by using a typewriter to type on paper. This does not involve strengthening.
- People can store information by drawing pictures or making paintings. This does not involve strengthening.
- People can store information by taking photographs, either by using digital cameras, or old-fashioned film cameras. In neither case is strengthening involved.
- People can store information by using tape recorders. This does not involve strengthening.
- People can store information by using computers. This does not involve strengthening.
So
basically every case in which we are sure information is being stored
does not involve strengthening. What sense, then, does it make to
claim that memory could be stored in synapses through strengthening?
In
all of the cases above, information is stored in the same way. Some
unit capable of making a particular type of impression or mark
(physically visible or perhaps merely magnetic) moves over or strikes a surface,
and a series of impressions or marks are made on the surface. Such a
thing is not at all a process of strengthening.
Consider
a simple example. You have a friend named Mary, and you one day learn
that Mary has a black cat. Now let us try to imagine this knowledge
being stored as a strengthening of synapses. There is no way we can
imagine such knowledge being stored by a strengthening of synapses.
If you happened to have stored in your brain the knowledge that Mary
has a black cat, it could conceivably be that a strengthening of
synapses might allow you to more quickly remember that Mary has a
black cat. But there is no way that the fact of Mary having a black cat
could be stored in your brain through a strengthening of synapses.
Every
protein molecule of a particular type has exactly the same chemical
contents – for example, every rhodopsin molecule has the same
chemical contents. Unlike nucleic acids, which can store strings of
information of indefinite length, a protein molecule cannot store
arbitrary lengths of information. So we cannot imagine that there is
some particular tweak of protein molecules added to a synapse (when
the synapse is strengthened) that would allow information to be
stored such as the fact that Mary has a black cat.
In
his Nautilus post “Here's Why Most Neuroscientists Are Wrong About
the Brain,” C. R. Gallistel (a professor of psychology and
cognitive neuroscience) points out the absurdity of thinking that
mere changes in synapse strengths could store the complex information humans remember. Gallistel writes the following:
What
Gallistel describes sounds dysfunctional: a pretentious
neuroscientist community that claims to understand how memory can be
stored in a brain, but cannot give anything like a plausible answer
to basic questions such as “How could a number be stored in a
brain?” or “How could a series of words be stored in a brain?”
or “How could a remembered image be stored in a brain?” Anyone
who cannot suggest plausible detailed answers to such questions has
no business claiming to understand how a brain could store a memory,
and also has no business claiming that a brain does store episodic or
conceptual memories.
Gallistel
suggests a radically different idea, that a memory is stored in a
brain as a series of binary numbers. There is no evidence that this
is true, and we have strong reasons for thinking that it
cannot be true. One reason is that there is no place in the brain
suitable for storing binary numbers, partially because nothing in the
brain is digital, and everything is organic. Another reason is there is no plausible physiology by which a brain could write or read binary numbers. Another reason is that
we cannot account for how a brain could possibly be converting words
and images into binary numbers. A computer does this through
numerical conversion subroutines and by using a table called the
ASCII code. Neither numerical conversion subroutines nor the ASCII
code is available for use within the brain.
In
short, the prevailing theory of memory storage advanced by
neuroscientists is untenable. Why do they advance this theory?
Because they have no better story to tell us. There is actually no
theory of a brain storage of memories that can stand up to prolonged
critical scrutiny. As discussed at length here, there is no part of
the brain that is a plausible candidate for a place where 50-year-old
memories could be stored. As discussed here, there is no part of the
brain that acts like a write mechanism for stored memory or a read
mechanism for stored memory.
What
our neuroscientists should be doing is telling us, “We have no
workable theory as to how a brain could store and instantly retrieve
memories.” But rather than admit to such a lack of knowledge, our
neuroscientists continue to profess the untenable synapse theory of memory. For
they want at all costs for us to stay away from a very plausible idea they abhor: that episodic and conceptual memory is a spiritual
effect (a capability of the human soul) rather than a neural effect.
Many
think that there is an exact match between the assertions of
scientists and observations. But this is not correct. The diagram
below shows something like the real situation. Claims such as the
claim that memories are stored in synapses are part of the blue area, along with many dogmatic and overconfident pronouncements such as string theory, multiverse speculations and evolutionary psychology.
The idea that memory is an aspect of the human soul rather than the
brain is supported not only by many observations in the green area of
the diagram (observations that a typical scientist would not
dispute), but also by many observations in the red area (such as the
massive evidence for psychic phenomena). See the posts at this site
for a discussion of very many of these observations.
Do not be fooled by the small number of scientific papers that claim to have found evidence for an engram or memory trace. As discussed here, I examined about 10 such papers, and found that almost all of them have the same defect: the number of animals tested was way below the standard of 15 animals per study group, meaning there is low statistical power and a very high chance of a false alarm. Besides a reliance on subjective judgments of freezing, the papers all deal with small animals, and don't tell us anything about human memory.
Do not be fooled by the small number of scientific papers that claim to have found evidence for an engram or memory trace. As discussed here, I examined about 10 such papers, and found that almost all of them have the same defect: the number of animals tested was way below the standard of 15 animals per study group, meaning there is low statistical power and a very high chance of a false alarm. Besides a reliance on subjective judgments of freezing, the papers all deal with small animals, and don't tell us anything about human memory.
I can give a baseball analogy for the theory that episodic and conceptual memories are stored in the brain. We can compare such a theory to a batter at the plate. If such a theory includes a plausible explanation of how human experiences and concepts could be stored as neural states, overcoming the extremely grave encoding problem discussed here, we can say the theory at least made contact with the pitched ball. If such a theory can credibly explain how memories could be written to the brain, we can say such a theory has reached first base. If such a theory can explain how a stored memory could last for 50 years, despite the very rapid protein turnover in brains and synapses, we can say such a theory has reached second base. If such a theory can explain how humans can so often instantly remember obscure things they learned or experienced decades ago, overcoming the seemingly insurmountable "finding the needle in a haystack" problem discussed here, we can say such a theory has reached third base. If such a theory were to be confirmed by someone actually extracting learned information from a dead brain, we can say such a theory reached home plate and scored a run. But using this analogy it must be reported that the theory of conceptual and episodic memory storage in the brain never even reached first base and never even made contact with the ball. For none of these things has been accomplished.
Postscript: The 2017 paper "On the research of time past: the hunt for the substrate of memory" was written by some leading neuroscientists. It states on page 9 that "synaptic weight changes can now be excluded as a means of information storage." The paper thereby disavows the main theory about memory storage that scientists have been pushing for the past few decades, the very theory I've rebutted in this post. The paper then suggests (in a pretty vacillating and tentative fashion) a variety of alternate possibilities regarding the storage of memory in the brain, none of which is suggested as the most plausible of the lot. See this post for why none of the alternate possibilities mentioned is a very credible idea.
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