On this site I have published several posts with titles beginning with "Exhibit A" or "Exhibit B." Each such post examined an article or paper which prevented prima facie evidence that neuroscientists are lacking in one of the basic things they often claim to possess. The posts are these:
Now let's look at another article or paper that offers this type of "Exhibit A": a 2021 paper by neuroscientist C. R. Gallistel entitled "The Physical Basis of Memory." The paper tells a "getting nowhere" story, and offers an excuse for the lack of progress: the extremely lame excuse that neuroscientists are too big fans of the 17th-century philosopher John Locke. The author states this:
"The unbreakable embrace of Locke’s theory by neuroscientists explains why we have still not discovered the physical basis of memory,
despite more than a century of efforts by many leading figures. Researchers searching for the physical basis of memory are looking for the
wrong thing (the associative bond) in the wrong place (the synaptic
junction), guided by an erroneous conception of what memory is and the
role it plays in computation. That is the hole we have dug for ourselves."
No, actually you can usually get a neuroscience PhD without even taking an introductory course in philosophy, and neuroscientists have not tended to be either big followers of any philosopher or people very interested in philosophy. Referring to "the engram" (an imagined neural or synaptic storage place of memory), the author then makes tells us that " the role of memory as the transmission
medium for the acquired facts that guide future behavior goes unmentioned in neurobiological reviews of the search for the engram (Poo
et al., 2016; Tomonori, Duszkiewicz, & Morris, 2013)." Oops, it sounds like our neuroscientist memory theorists are dropping the ball. The author then claims that the neuroscience literature "documents beyond reasonable argument that brains contain facts." No, that is not true; we merely know that humans and animals learn facts, not that brains contain facts.
The author offers this evidence for the claim that "the brain contains facts": the fact that the average English speaker knows 40,000 words and that "the cognitive science literature
shows that we can remember thousands of drawings of objects and
thousands of boring vacation slides and the even more boring target and
distractor items in visual search experiments—objects and scenes and
drawn objects that we have seen or felt or smelled only once for a few seconds or less seconds or less (Brady, Konkle, Alvarez, & Oliva, 2008; Hutmacher &
Kuhbandner, 2018; Konkle, Brady, Alvarez, & Oliva, 2010; McGann,
2017; Shepard, 1967; Standing, 1973)." That is merely evidence that humans can remember things, not that brains store what we remember.
What some of these experiments show is that humans can form long-term memories of things seen for only a few seconds, things seen only a single time (something we need no experiments to prove, since this ability is a common fact of everyone's experience). Far from supporting claims that memories are stored in brains, such studies conflict with or clash with such claims. The ability of humans to instantly form new memories is something that no neuroscientist can credibly explain. Existing hand-waving speculation about "synapse strengthening" as a cause of memory formation are inconsistent with the ability of humans to instantly form new memories, because such synapse strengthening would require new protein synthesis taking many minutes. That's why you often hear neuroscientists make the ridiculous claim (contrary to every person's experience) that humans take minutes to create a new memory.
The author then gives us a long paragraph discussing how humans and animals compute things. Why mention that in a paper entitled "The physical basis of memory"? Maybe because no such physical basis is known, so if the "physical basis of memory" is your topic, you have to fill up your pages saying something. On and on the author goes, talking at length about topics such as dead reckoning (a distance estimation ability) and other topics that have nothing to do with a physical storage of memory.
After wandering around for several long paragraphs about mostly irrelevant topics, the author then fires another broadside against his fellow neuroscientists:
"In order to pass into and through a channel of communication, a
message must be encoded (Shannon, 1948). Therefore, those of us
pursuing the material basis of memory must ponder what the code might
be and how it could be physically realized (Gallistel, 2017a, 2017b) This
question about the memory code makes neuroscientists deeply uncomfortable, for which reason, it is never posed in the vast literature on the
neurobiology of memory."
That's pretty much correct, although it might have been more fair to have said "almost never posed" than "never posed." It is easy to understand why neuroscientists virtually never make any attempt to suggest a possible encoding scheme by which a brain might physically store memories. The reason is that humans learn and remember so many different types of things that any such encoding scheme would have to be almost infinitely more complicated than the one known coding scheme used by the body (the genetic code by which triplets of nucleotide base pairs stand for particular amino acids). If such an encoding scheme existed it would have to be some miracle of design more complex than any coding scheme humans have ever invented. It would be impossible to explain how such a coding scheme (capable of storing text using alphabets and musical notation schemes only a few thousand years old) could have naturally arisen by evolution. So neuroscientists pretty much ignore the whole problem of neural encoding.
Our author rambles on and on, mostly on digressions that have nothing to do with how a brain could physically store a memory. In his second to last paragraph he claims that "polynucleotides" are "the only biological
structures that are known to function as transmitters of information." But haven't we been told a thousand times that axons transmit sensory information to the brain from the eyes? Axons are not polynucleotides, but wire-like structures. In his last sentence the author dismisses the leading claim of neuroscientists about how a brain stores memories (the very vague idea of "synapse strengthening") and offers only the equally vague catchphrase of "information-bearing molecules" as an alternative. He states as his last sentence, "The material realization of the engram
is probably not to be found in the synapse, much less in multi-neuron cell
assemblies (the neural equivalent of Locke’s dust-ball concepts); it is to
be found in information-bearing molecules inside neurons, operated on
by molecular level computational machinery (Akhlaghpour, 2020)."
We end up with the author having presented no theory as to how there could be any physical basis of memory. All he's done is to make a lame excuse involving the claim that neuroscientists were too influenced by John Locke, and given us a link to some paper by Akhlaghpour. An examination of the paper by Akhlaghpour will leave you disappointed.
The paper by Akhlaghpour is entitled "An RNA-Based Theory of Natural Universal Computation." Akhlaghpour is not a professor, but merely a post-doctoral fellow. The paper starts out very badly in its first paragraph by stating, "Some examples of computation in biology include: using vision to guide wing movement in insect flight, language acquisition in humans, decision making in single celled ciliates [1,2], and embryonic development, the decisional process of beginning with a single cell and coordinating across daughter cells to produce a complex finely detailed three dimensional structure." No, language acquisition is not an example of computation, nor is embryonic development. A baby does not form by computation. Morphogenesis is an example of extremely complex physical three-dimensional organization and construction, which is not mere computation. The Merriam Webster dictionary defines computation as "the action of mathematical calculation" or "the use of computers, especially as a subject of research or study."
At the end of page 7 Akhlaghpour says, "I propose the theory that the nonprotein coding portion of genome and transcriptome contains the data and programming material of an undiscovered universal computation system in biology." So vague an idea is best described as a hypothesis rather than a theory. We then have the presentation of some extremely far-fetched speculations imagining that DNA or RNA might have all kinds of marvelous properties that no one has ever discovered in them. On page 16 these speculations go astray by trying to convince us that nucleic acids could have an addressing system. We read this:
"The method of nesting terms through RNA stem loops presents an opportunity to implement addressable memory
and variable substitution. One such implementation is illustrated in Fig 6. In this model, each variable is assigned
an address (specified by a unique sequence of nucleotides)."
DNA has been exhaustively analyzed, and no such thing has been found. There is no evidence of any addresses or addressable memory anywhere in DNA, RNA, or anywhere in the brain.
On page 22 Akhlaghpour discusses what seems like a fatal difficulty for his theory:
"Another challenge for a solely RNA based molecular engram theory is RNA stability. If a molecule were to serve as a memory engram it must at least exhibit stability over similar time periods as cognitive memories. RNA molecules have an average half life of around 7 hours."
Nothing that he says extracts himself from this problem. He mentions the possibility of RNA storing data back into DNA. But that would be like a giant steel ball chained to the leg that would slow things to a crawl, preventing the instant memory recall we know occurs.
On the same page Akhlaghpour attempts to convince us that his RNA scheme could be fast enough, stating this:
"Can RNA modifications occur fast enough to potentially facilitate cognition? Two of the most well studied RNA
processes are transcription and translation. RNA Polymerase II transcribes RNA molecules at a rate of 18-100 nt/s
equivalent to 36-200 bits/s [bits per second]. And the ribosome translates RNA to protein at a speed of roughly 511
aa/s equivalent to 30-66 bits/s [bits per second]. It is difficult to quantify how fast animals think but studies of different
languages show that the information rate of human speech is roughly on the order of 40 bits/s (languages that
are spoken faster have lower bits per syllable than languages that are spoken slower)....This means that RNA operations can in principle be fast enough to encode/transmit
ideas communicated in speech as single RNA molecules."
There are several things wrong here. First, the rate at which RNA can be translated to protein is irrelevant here, if we are imagining a memory is read from DNA. The relevant rate is the rate of transcription, the rate at which DNA is read to produce RNA. Akhlaghpour has overstated the speed of RNA transcription (reading DNA to produce RNA). The recent paper here lists the speed of RNA Polymerase II transcription as less than 4 kilobytes per minute, which is less than 67 bytes per second. Also it is not true that humans recall at only 40 bits per second. A slow old man like me can clearly sing the first four lines of Gilbert and Sullivan's "I Am the Very Model of a Modern Major General" song at a rate of 204 bytes in 7.5 seconds, which is a rate of 218 bits per second. That means people can recall things at a speed three times faster than the speed of RNA transcription just quoted. Even without considering the problem of "finding the right spot to read at," it turns out reading from DNA would be three times too slow to account for fast human memory recall. So it is not true that " RNA operations can in principle be fast enough to encode/transmit ideas communicated in speech as single RNA molecules," as Akhlaghpour claims.
But you must also consider that there is no sorting, no addresses and no indexes anywhere in the brain or DNA or RNA (contrary to the chimerical imaginative speculations of Akhlaghpour). That means trying to recall the correct answer when asked a question or asked to recite something (using brain memory storage) would proceed at a rate very many thousands of times slower than a rate of 67 bits per second, because there would be the enormous "finding the needle in the haystack" speed delay of having to find exactly the right spot where a memory was stored in the brain or its DNA, and a brain would never know where that exact right spot was.
Akhlaghpour is trying to make use of some abstract computer science notions of "universal computation" and a "Turing machine" that is built upon the idea of some machine that takes a line-like one-dimensional paper feed of characters and produces output that is also a one-dimensional paper feed of characters, rather like a stock ticker. Computer science calculations about such a machine are not applicable to a mind. Rather than receiving a single line of characters, a human mind simultaneously receives inputs from lots of different sources:
- visual input that is vastly more complex than just a one-dimensional stream of characters;
- auditory input;
- touch input from the hands;
- smell input;
- taste input;
- memory recall input.
And similarly, rather than producing any one-dimensional output such as a line-like stream of characters, mental activity can produce three-dimensional output such as the simultaneous singing, expressions and dancing of a Broadway performer.
On the next page (page 23) Akhlaghpour makes the little confession that under the byzantine speculative scheme he is imagining, the mere addition of one number to another would require something like 10,000 operations. But then on the same page he brags that his scheme is not evoking "implausible molecular processes." Such a boast is untrue, and the molecular processes evoked are utterly implausible and unworkable as any explanation for human memory performance. He notes that "current theories of synaptic plasticity and network activity cannot explain learning, memory, and cognition."
Akhlaghpour's theory ends up being nothing that can explain memory. His paper has mainly been busy trying to create some "castle in the clouds" theory of universal RNA computation that has nothing to do with explaining memory. As kind of a sideshow, he says a little related to explaining memory, but it's a half-hearted affair that does not nudge the giant rock of this Everest-sized problem.
Human DNA has been exhaustively studied in all parts of the brain. Contrary to Akhlaghpour's theory:
- No one has ever found any evidence of human conceptual information (such as school-learned information) by studying brain tissue or DNA from brains.
- No one has ever found any evidence of human episodic memories (such as images seen or sounds heard) by studying brain tissue or DNA from brains.
- No one has ever found any sign of any addresses, indexing or sorting (or anything else that could explain instant human recall) in human brain tissue or DNA from brains.
- Computing as occurs in computers requires things such as an operating system (an incredibly complex coordinated body of low-level software routines) and lots of application software. There is not the slightest sign of any such thing in the human brain.
- No one has ever found any sign of any coding system or encoding system in human brain tissue or DNA from brains, except for the genetic code used by every cell in the human body.
Summarizing the paper of C. R. Gallistel entitled "The Physical Basis of Memory." we can say that it does very little but complain that current theories offer no credible physical theory of memory, and then ends up by giving a link to some speculative paper that also completely fails to offer any credible physical theory of memory. The excuse Gallistel gives for why scientists have found no physical basis for memory (that brain scientists were too big fans of John Locke) is a ridiculous-sounding excuse. A much better explanation is that scientists have got nowhere on the quest for a brain physical basis of memory simply because brains do not store memories.
Memory must be something like a spiritual reality rather than a neural reality. It isn't true, as many think, that we have souls or spirits that come into play only during unusual psychic experiences or religious experiences. Instead, the most basic processes of our minds such as thinking and insight and remembering must utilize human non-physical capabilities and abilities. We don't form new memories or recall answers at the very sluggish speed of brains; we acquire new memories and recall answers at the speed of souls.
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