The Lack of a Viable Theory of Neural Memory Encoding

The Lack of a Viable Theory of Neural Memory Encoding



If we are to believe in the claim that brains store human memories, we must have a credible account of four things: encoding, neural storage of very old memories, the instantaneous formation of memories, and the instantaneous retrieval of memories. The theory that human memories are stored in the brain fails in regard to each of these things.

There exists no plausible theory as to how a brain could store memories lasting for 50 years, but we know humans can remember many things for that long. The most popular idea of brain memory storage claims that memories are stored in synapses, but the proteins in synapses have an average lifetime of less than two weeks, meaning such a theory falls short by a factor of 1000 when it comes to explaining memories that persist for 50 years. As for memory retrieval, there is no theory explaining how humans could possibly recall instantly things they learned many years ago, and haven't thought about in years. You may hear the name of some obscure historical or cultural figure you learned about decades ago, and haven't heard about or thought about since that time. You may then instantly recall something about that person. But if that memory was stored somewhere in your brain, how could you instantly find the exact little location where that memory was? Doing that (for example, instantly finding a memory in storage spot 834,220 out of 1,200,000) would be like instantly finding a needle in a mountain-sized haystack. If a brain had an indexing system, or a coordinate system, or a neuron numbering system, there might be a faint hope for explaining instantaneous memory retrieval; but the brain has no such things. As for the instantaneous formation of memories, there is no theory that can account for it in a brain. The prevailing theory that memories are stored by synapse strengthening (which would involve protein synthesis requiring minutes) fails to account for memories that humans can form instantly.

When we consider the issue of memory encoding, we find a difficulty as great as the difficulties just discussed. Encoding is supposedly some translation that occurs so that a memory can be physically stored in a brain, so that it might last for years. The problem is that human memories include incredibly diverse types of things, and we have no idea how most of these things could be stored as neural states. Consider only a few of the types of things that can be stored in a human memory:

  • Memories of daily experiences, such as what you were doing on some day
  • Facts you learned in school, such as the fact that Lincoln was shot at Ford's Theater
  • Sequences of numbers such as your social security number
  • Sequences of words, such as the dialog an actor has to recite in a play
  • Sequences of musical notes, such as the notes an opera singer has to sing
  • Abstract concepts that you have learned
  • Memories of particular non-visual sensations such as sounds, food tastes, smells, pain, and physical pleasure
  • Memories of how to do physical things, such as how to ride a bicycle
  • Memories of how you felt at emotional moments of your life
  • Rules and principles, such as “look both ways before crossing the street”
  • Memories of visual information, such as what a particular person's face looks like

How could all of these very different types of information ever be translated into neural states so that a brain could store them?

Our neuroscientists have told us again and again that the brain does such an encoding, but there is no real evidence that any such thing takes place. What we have evidence for is merely evidence that humans remember things. If you are someone who believes that memories are physically stored in brains, then you may claim that memory encoding occurred at such and such a rate whenever you observe people learning something at such and such a rate. But merely observing evidence of learning or memory is not acquiring any actual evidence that encoding has occurred. There remains the possibility that our memories are not stored as neural states, the possibility that our repository of memory is some spiritual or psychic facility that is non-neural and non-biological.

Such a possibility should not seem remote when we consider that there is no workable theory as to how learned knowledge and experiences could be encoded so that they might be stored in a brain. No matter what theory we may create to account for the encoding of learned knowledge and episodic experience so that they can be stored in a brain, such a theory will always end up sounding ridiculous after we examine the theory in detail and consider its requirements and shortcomings. Let's look at some possibilities, and why they fail.

Theory #1: Direct writing of words and images

First, let's consider the simplest theory of encoding we can imagine – that a memory is stored in the brain so that it appears in a neural form pretty much as we see it in our minds. Under this theory, when you memorized some series of words, this would cause a sequence of microscopic little letters to become stored in your brain; and when you experienced some visual experience, this would get stored as some tiny little image in your brain. So, for example, under this theory, if someone memorized the sentence, “There may be green aliens in the center of the galaxy,” then after the person died, some scientist might examine that person's brain with an electron microscope, and actually find some tiny little words in some neurons, words that directly spelled out, “There may be green aliens in the center of the galaxy.” And under this theory, if someone was given a picture of a toy purple pony, and asked to memorize it, then after the person died, a scientist might be able to examine the person's brain under an electron microscope, and the scientist might say, “Aha, I see in his neurons a tiny little image of a toy purple pony.”

This theory may immediately provoke giggles, and it is rather easy to think of some reasons why it does not work. They are these:

  1. If memory worked in such a way, we would surely have already discovered such easily-recognizable memory traces. But no such things have been seen, even though a great deal of human neural tissue has been examined at very high magnification. When we look at brain tissue at the highest magnification, we see no tiny little letters or tiny little images of animals, cars, and persons.
  2. For a brain to be able to write words that we memorized in this type of direct manner, it would seem that the brain would need some very precise write mechanism, capable of forming the exact characters of the alphabet in brain tissue; but no such brain capability is known to exist.
  3. It seems that if such a theory were true, recalling some words would be like reading. But recalling words is almost never like reading, and we don't see in our mind's eye some stream of letters as we recall some words we memorized.
  4. For a brain to be able to read words that we memorized in this type of direct manner, it would seem that the brain would need some very precise reading mechanism, capable of reading the exact characters of the alphabet stored in very tiny letters written in brain tissue; but no such thing is known to exist. We don't have tiny little “micro-eyes” in our brains that might allow us to read tiny microscopic letters stored in our brains.

Theory #2: Brain storage of words and images using some unknown non-binary coding or translation protocol

Now, let's consider a different theory of memory encoding – the idea that instead of directly storing words and images (so that we could directly read the words and directly see the images), the brain uses some type of unknown coding or translation protocols. For example, it could conceivably be that words that we learn are somehow translated into proteins or chemicals or electrical states, using some as-of-yet undiscovered translation scheme.

For example, such a scheme might work a little like this:

Item How the item might be represented
Letter “A” Some particular neural arrangement of atoms, chemicals or electricity
Letter “B” Some other neural arrangement of atoms, chemicals or electricity
Letter “C” Some other neural  arrangement of atoms, chemicals or electricity

Such a scheme might work a little like the Morse code, in which particular letters are translated into some sequence of dots, dashes, or dots and dashes. Some particular arrangement of atoms, chemicals or electricity might work like a dot in the Morse code, and some other particular arrangement of atoms, chemicals or electricity might work like a dash in the Morse code.

Or there could be some higher-level translation system based on particular words rather than letters. For example, we can imagine something like this:


Item How the item might be represented
Word “sun” Some particular neural arrangement of atoms, chemicals, proteins or electricity
Word “man” Some other neural arrangement of atoms, chemicals, proteins or electricity
Word “move” Some other neural  arrangement of atoms, proteins chemicals or electricity

There is one giant problem with such a theory. All of the languages that we use are fairly recent innovations, having been created in only the last few percent of the time that humans have existed. For example, back in the Roman Empire people used Latin, but the English we use today has only been in use for less than 1200 years. The alphabet used for English is less than 1000 years old, and its alphabetic predecessor (the Latin alphabet) is only a few thousand years old. It is generally acknowledged even by Darwinism enthusiasts that very complex evolutionary innovations cannot arise in only a few centuries of time or a few thousand years. So we could never explain how the brain could naturally possess some elaborate translation system based on such a relatively recent innovation as the English language and the English alphabet.

Scientists strain our credulity whenever they talk about novel functional genes accidentally appearing even over the course of a million years. Think, then, on how much greater a problem there would be in explaining how hundreds of novel functional genes could have appeared in less than 3000 years, to perform some translation operation involving characters and words that have existed for less than 3000 years. To assume such a thing would be to assume evolution working thousands of times faster than the rate we would predict from known mutation rates.

There is also no evidence that any such great burst of genetic novelty has occurred. Although the half-life of DNA is 512 years, we have enough samples of human DNA from ancient Rome and ancient Egypt to know that there has been no big change in the DNA of humans during the past 3000 years. So it seems impossible that there could be any genetic capability (arising in the past few thousand years) that would allow humans to neurally store information using some encoding mechanism specifically tailored to the letters and words of the English language that have existed for less than 3000 years.

Another difficulty with the theory of encoding just mentioned is that if it existed, we would see big differences in the genes of people who spoke different languages. According to such a theory, we would expect that Chinese people would have one group of genes corresponding to proteins or RNA molecules needed to translate Chinese words into neural states, and that English speaking people would have some other quite different set of genes corresponding to proteins or RNA molecules needed to translate English words into neural states (particularly since the Chinese language and alphabet is so different from the English language and alphabet). But there exists no such difference in the genes of Chinese speaking people and English speaking people.

There is also the difficulty, discussed more fully in the conclusion of this post, that there is no sign in the human genome that any such genes exist for performing such an elaborate operation of encoding human learned knowledge and episodic experience so that it can be stored in neurons or synapses (and there would need to be many hundreds or thousands of genes dedicated to performing such a task if it was done).

Theory #3: Binary writing of words and images

Now, let's consider a theory of memory encoding that perhaps the words we memorize and the images we remember are stored in binary format. We know that computers store information in binary format, so when it is suggested that the brain may use a similar format, this may sound reasonable to the average person (although it isn't, a brain being radically different from an electronic computer).

This possibility actually has all of the difficulties of the previous possibility. What goes on when your computer stores words in binary format is the following:

  1. First individual letters in the words are converted into decimal numbers (such as 13, 19, and 23) using a particular translation table called the ASCII code.
  2. Then, those numbers are converted from decimal to binary using a decimal-to-binary conversion routine.

So if we are to believe that the brain does binary encoding like a computer, we would need to believe that built into the brain on a low level is some type of translation scheme like the one below, a scheme in which letters are translated into decimal numbers.

ASCII table used by a computer to store encoded information

In addition, we would also have to believe that the brain has some kind of capability to translate the numbers in such a system into binary numbers. Alternately, we could believe that the brain has a scheme for directly translating characters into binary, but the overall complexity of such a translation mechanism would be every bit as great as a system in which characters are converted into decimal, and then into binary.

We have the following difficulties involved with such an idea:

  1. If memory worked in such a way, we would surely have already discovered such easily-recognizable memory traces. We would have discovered tiny little traces in the brain that resemble binary coding. But no such things have been seen, even though a great deal of neural tissue has been examined at very high magnification.
  2. For a brain to be able to write words that were memorized in this type of direct manner, it would seem that the brain would need some very precise write mechanism, capable of writing binary traces; but no such thing is known to exist.
  3. For a brain to be able to read words that we memorized in this type of direct manner, it would seem that the brain would need some very precise reading mechanism, capable of reading in binary; but no such thing is known to exist.
  4. Since the alphabets of human languages are only a few thousand years old, there would have been no time for the human body to have evolved some complex biological mechanism capable of converting specific alphabetic characters to binary.
  5. We can imagine no way in which a brain could achieve the translation effect in which words are translated into binary. As far as we know, there is nothing anything like an ASCII table in your brain, nor is there anything like a facility for translating English letters directly into binary, nor is there anything like a facility for translating English letters into decimal, and then translating decimal numbers into binary. There are no genes in the genome that perform such tasks.

Theory #4: Storage of sensations occurring when something is learned or experienced

Now, let's consider a whole different theory. It could be that instead of storing words that you memorized, a brain might store the sensations that occurred when you memorized something. So imagine I open up a copy of Vogue magazine, and read an ad saying, “You'll feel fresher than the morning dew.” If I memorize that slogan, it might be that my brain is storing the electrical or chemical activity in my brain when I saw that slogan. And if I hear on the radio some advertising slogan of “We'll build your wealth sky-high,” and memorize that, it could be that my brain is storing something corresponding to the electrical and chemical activity in my brain when I heard such a slogan.

One reason for doubting this theory of memory encoding is that perceptions involve large parts of the brain, and it is hard to imagine that sensations involving large fractions of the brain could be stored in a tiny part of the brain. Since our minds store many thousands or millions of visual memories, if we are to believe that memories are stored in brains, we would have to believe that each stored memory uses only a tiny portion of the brain. But my current visual sensations require the involvement of a large fraction of the occipital lobes of the brain – probably many cubic centimeters. But we cannot plausibly imagine that the brain simply dumps the chemical or electrical contents of those cubic centimeters into some memory that took up only a tiny space on my brain, a millionth or less. It would seem, therefore, that if the brain simply dumped your visual and auditory sensations into memory, that it would require a space vastly bigger than itself to store all the memories we have of things we have seen and heard.

Another difficulty in the “memories are sensation dumps” idea is that there is no evidence of any mechanism for copying information from one part of the brain to another. Let's imagine that when a memory forms, the state of your occipital lobes (involved in vision) is copied to some point on the cortex where the memory is stored. That would require some biological functionality for copying the state of one large part of the brain to another part of the brain; but we know of no such functionality.

It is easy to think of another big reason for doubting such a theory. It is that if our brains were to be storing something corresponding to sensations, we would expect that when we remembered words, we would remember something visual, with a characteristic font or color, or something auditory, with a characteristic sound. But while that sometimes happens, in almost all cases it does not work that way.

For example, if I remember the words, “Here's looking at you, kid,” I do remember a very specific audio sound, the distinctive sound of Humphrey Bogart saying that in the movie Casablanca. And if I remember the phrase “Men walk on moon,” I do remember a specific font, the font used in the famous New York Times headline of the Apollo 11 lunar mission. But a very large fraction of my memories do not have specific visual or audio characteristics. For example, if someone asks, “What is the lightest particle in an atom?” I may reply, “The electron is the lightest particle in the atom.” But that memory I have recalled does not have any specific sound or sight associated with it. I don't hear the answer in someone's voice, and I do not see the answer as words in any particular font or color. And if someone asks me, “What is your birthday?” I will remember a particular day. But I will not see in my mind's eye some date written in a particular font and having some particular color, nor will I hear in my mind's ear some particular type of voice stating the answer.

For almost all of my knowledge memories, the same thing is true: when I recall the memory, I don't see something that appears with some particular visual appearance, nor do I hear something that has some particular sound. It seems this would not be the case if the brain was storing my memories by storing visual and auditory sensations.

It is also true that I can memorize something that does not correspond to any particular visual or auditory sensation I had. For example, I can visualize some imaginary thing such as a giant purple elephant. If I think about this imaginary thing enough times, it will become a permanent memory. But this imaginary thing I have memorized does not correspond to any sensation I had. In this case I never saw a giant purple elephant. So it cannot be that my memory of the giant purple elephant was formed from sensations that I had of such a thing. Similarly, a fiction writer can dream up on Tuesday an idea for a short story, and then write that short story on Wednesday, using the memory he formed on Tuesday. But the memory will not correspond to any visual or auditory sensations he had.

It seems that we therefore cannot explain memories as merely being a storage of sensations that we had at some time when we learned something. You learned many thousands of things in school, but when you remember such knowledge, you virtually never remember the sight and sound of your school teacher teaching you such things or the sight of you reading a book telling you such things (as you would if your memory of learned knowledge was just a dump of the sensations you had when you learned such things).

Conclusion

I have reviewed some of the theories that could be used to account for the encoding of learned information as neural states. There are strong reasons for rejecting each such theory. It seems it is impossible to present a specific theory of memory encoding that stands up to scrutiny as a reasonable possibility. 

How is it that neuroscientists sidestep this difficulty? They simply avoid presenting specific theories of how a brain could translate learned information into neural states. An example is the wikipedia.org article on “Memory (encoding).” The article tells us, “Encoding allows the perceived item of use or interest to be converted into a construct that can be stored within the brain and recalled later from short-term or long-term memory.”
But the article fails to discuss any specific theory discussing how such a conversion would work. The article has all kinds of digressions and tangential information, but nowhere does it advance a single specific idea of how learned information (such as a learned sequence of words) could be translated into neural states when a memory was stored in a brain. An article on a memory experiment states, "Press a scientist to tell you how memories are encoded and decoded in the brain, and you’ll soon find that the scientific community doesn’t have an answer."  In his book Crimes of Reason: On Mind, Nature, and the Paranormal, philosopher Stephen Braude says on page 19 that neuroscience "never addresses the fundamental issues of how any physical modification can represent or stand for what is remembered." 

A speculative neuroscience paper confesses that "codifying memories is one of the fundamental problems of modern Neuroscience," but that "the functional mechanisms behind this phenomenon remain largely unknown."  It would have been more accurate to have stated "entirely unknown." 

Just as it is impossible to advance a credible detailed theory as to how Santa Claus could distribute a toy to every good little boy and girl in the world in a single 24 hours, it is impossible to advance a credible detailed theory of how learned knowledge and episodic experience could be encoded and permanently stored as neural states. If memories were to be encoded so that they could be stored in brains, there would be two major “footprints” of such a thing, physical traces showing that it was going on. They are the following:

High repetition of representational building blocks. Whenever encoded information is stored, there is a repetition of two or more things we can call representational building blocks or representational atoms. In binary encoding these representational building blocks are the 1's and 0's or their electromagnetic equivalent. In alphabetic encoding, the representational building blocks are the letters of the alphabetic. In DNA the representational building blocks are the four types of nucleotide base pairs that are repeated over and again. In Morse code, the representational building blocks are dots and dashes. Even if you don't know the system of encoding that was used, it is easy to detect that encoded  information is present, by seeing a high repetition of representational building blocks. If brains stored memories encoded into neural states, we would see a gigantic degree of repetition of some type of representational building blocks.
Genes dedicated to memory encoding. If human brains were to actually be translating thoughts and sensory experiences so that they can be stored as memory traces, such a gigantic job would require a huge number of genes – many times more than the 500 or so genes that are used for the very simple encoding job of translating DNA nucleotide base pairs into amino acids.

There is no sign at all of either of these things in the brain. We absolutely do not see anything like very highly repeated representational building blocks in the brain that might be the footprints of encoded memory information. And we see no sign of any such memory encoding genes in the human genome.

There is a study that claims to have found possible evidence of memory encoding genes, but its methodology is ridiculous, and involved the absurd procedure of looking for weak correlations between a set of data extracted from one group of people and another set of data retrieved from an entirely different group of people. See the end of this post for reasons we can't take the study as good evidence of anything. There is not one single gene that a scientist can point to and say, “I am sure this gene is involved in memory encoding, and I can explain exactly how it works to help translate human knowledge or experience into engrams or memory traces.” But if human memories were actually stored in brains, there would have to be thousands of such genes.

memory encoding

There is an additional general difficulty involved in the idea that brains encode our episodic experiences and learned knowledge as neural states. It is that if the brain did such a thing, it would require a translation facility so marvelous that it would be a “miracle of design,” something that we would never expect to ever appear by unguided evolution.

Yet another problem is that if brains encoded learned knowledge and episodic experiences into engrams or memory traces,  then forming new memories would be slow, and retrieving memories would be slow -- for whenever we formed a new memory, all kinds of translation work and encoding would have to be done (which would take a while), and whenever we retrieved a stored memory, all kinds of decoding work would have to be done (which would take a while).  But instead humans can form memories instantly and retrieve memories instantly, much faster than things would work if all this encoding and decoding work had to be done. 

What has been discussed here is only a small fraction of the very large case for thinking that human cognition and memory must be some psychic or spiritual reality rather than a biological or neural reality.  

Let's imagine a boy who thinks that his mother will give him a pony for Christmas. December 25th comes, and the boy searches everywhere around his house and yard; but there's no pony. On December 28th, having spent several more days looking for such a pony without success, the boy says, "There must be a pony around here somewhere."  We may compare this boy to the modern neuroscientist who believes there are brain engrams that encode our learned knowledge, but who still hasn't found such things, despite decades of searching. He says to himself, "They must be somewhere in the brain." But if they existed, they would have been found long ago.  There is microscopic encoded information in DNA (specifying the amino acids in proteins). Unmistakable evidence of that was discovered around 1950. Why would it possibly be that we would have failed to discover encoded memory information in a brain by the year 2018, if such information actually existed in brains? It would be as easy to find as the genetic information in DNA.