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Our future, our universe, and other weighty topics


Sunday, August 12, 2018

Two Reasons the Synapse Theory of Memory Storage Is Untenable

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:

  1. People can store information by writing using a paper and pen. This does not involve strengthening.
  2. People can store information by using a typewriter to type on paper. This does not involve strengthening.
  3. People can store information by drawing pictures or making paintings. This does not involve strengthening.
  4. People can store information by taking photographs, either by using digital cameras, or old-fashioned film cameras. In neither case is strengthening involved.
  5. People can store information by using tape recorders. This does not involve strengthening.
  6. 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:

It does not make sense to say that something stores information but cannot store numbers. Neuroscientists have not come to terms with this truth. I have repeatedly asked roomfuls of my colleagues, first, whether they believe that the brain stores information by changing synaptic connections—they all say, yes—and then how the brain might store a number in an altered pattern of synaptic connections. They are stumped, or refuse to answer....When I asked how one could store numbers in synapses, several became angry or diverted the discussion with questions like, “What’s a number?”

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.


scientist overconfidence
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. In a later post (but not my next post) I will explain why none of the alternate possibilities mentioned is a very credible idea.