I read the page carefully, hoping for clarification on the seemingly insurmountable problem of explaining how a brain could instantly retrieve a memory. One aspect of this problem is what I call the navigation problem. This is the problem that if a memory were to be stored on some exact tiny spot on the brain, it would seem that there would be no way for a brain to instantly find that spot. For that to occur would be like someone instantly finding a needle in a gigantic haystack, or like someone instantly finding just the right book in a vast library in which books were shelved in random positions. Neurons are not addressable, and have no neuron numbers or neuron addresses. So, for example, we cannot imagine that the brain instantly finds your memory image of Marilyn Monroe (when you hear her name) because the brain knows that such information is stored at neural location #235355235. There are no such "neural addresses" in the brain.
Then there is also the fact that the brain seems to have nothing like a read mechanism by which some small group of neurons are given special attention. The hard disk of a computer has a read/write head, but there's nothing like that in the brain. Then there is the fact that if memory information were encoded into neural states, the brain would have to decode that encoded information; but such a decoding would seem to require time that would prevent instantaneous recall.
There are 68 "expert answers" on the ResearchGate.net page, but only 1 of them is rated as a “popular answer” by the site. This one “popular answer" is simply to a link to a speculative paper talking about some weird and not-currently-popular “holographic” theory of memory. The paper says this at its beginning:
"Yet, all attempts to describe human memory as a hologram have failed up to now. Hence, the holographic brain hypothesis is simply ignored in neuroscience textbooks. Probably, my attempt will fail too."
So the most popular answer on the page is one in which the author does not sound like she has much confidence in her claims. I will now review some of the answers on the page, going from its top to its bottom. One of the first answers (given by one Richard Traub) states the following:
"I have no doubts at all that the mechanisms controlling retrieval are a collaborating team of high-level cognitive, affective and motorically-influence & influencing subsystems that encode and identify specific circumstantially relevant goals and, in terms of which, index circumstantially relevant sensory circuit assemblies - the computed output of which causes a top-down activation of the decided-upon distributed assemblies and consequent re-representation of their own combined output in the earlier event of analyzing, perceiving and mapping the "live" stimuli upon which a particular episodic memory was originally founded."
This gobbledygook may sound impressive, until we realize that there is no real theory behind it at all, except for the idea that when a memory is recalled the brain is replaying the sensory experience that caused the memory to form. That does nothing to explain how the brain could find the exact location of the correct tiny spot where a memory was stored. We also know that the basic idea of this "replaying sensory experience when you learned something" theory is not correct. When someone asks me how many states are in the United States, my mind does not play back the sensory experience I had when I first learned that the United States consists of 50 states. And if someone asks me who killed Abraham Lincoln, I do not play back the sensory experience of my fifth-grade teacher telling me that John Wilkes Booth did this act.
The next answer is from an Engineering PhD named Mells who admits, “I don't have an immediate answer to the retrieving of 'old' data.” This is followed by a humble answer by Simon Penny that offers no theory or explanation. We then have an answer by Salman Zubedat, who works at a neuroscience lab, but merely refers to speculative theories of neural memory storage, without mentioning any theory or explanation for memory retrieval.
We then have an answer from Herwig Lange, a neuroscientist who says nothing in answer to the question “How are memories retrieved in the brain?” other than, “He who finds out wins the next Nobel-prize.” We can interpret this as a confession that neuroscientists do not currently understand how a brain could retrieve a memory.
We then have an answer from physiologist Sutarmo Vincentius Setiadji who states the following:
"New experience firstly stimulates some components of sensory organs. These organs then stimulates some neural circuits in the higher parts of nervous system and then stimulate one or more primary sensory cortex/cortices. These stimulations go to uniassociation cortex or also directly to multi association cortex. From there through entorhinal cortex go to the hippocampus for being processed for several times. After that from hippocampus will be sent back through entorhinal cortex to multi association cortex as long term memory."
This is not an explanation as to how a brain could find the exact location at which a memory is stored, nor is it an explanation of how any reading effect could occur from such a location. The account above basically amounts to saying that sensory experience causes electricity to start traveling around between different parts of the brain, but that doesn't explain memory retrieval. Moreover, memory retrieval very often occurs without sensory experience being the start of things. For example, I may start randomly recalling my mother, without seeing anything that caused such a memory retrieval.
Then we have Ursula Ehfield offering the not-very-clear poetics below:
"As to my view it is a huge concert of waves and oscillations involved. (EEG are very important as a 'global player'!) Any neurotransmitter population plays its own concert. Sometime the piano starts, sometime the violin, sometimes the trumpets, which ever is resonating first."
We then have a rather long argument back and forth between Ehfield, Setiadji, and Graeme Smith. Within that argument we do not get any real explanation for how a brain could retrieve a memory.
We then have an answer from psychology PhD John S. Antrobus who tells us that memories are not retrieved but activated, and then merely says, “After that, the answer could fill a book.” Later on in the page John gets more detailed, although he isn't really telling us anything. He states the following:
"Lexical recognition of a word is accomplished by the activation of the neurons that represent that word, and the suppression of all others. Auditory word recognition requires another network. The 'meanings,' syntax, motor networks of speech, typing, etc., pictorial representation, values, and other features are accomplished by reciprocal circuits, largely in the prefrontal cortex. Any of these may play a part in activating the lexical representation, and may modify the largely 'bottom-up' recognition network. All, and in different ways, are part of the 'memory' of the lexical representation in that they are able to activate [or] suppress the activation of the neurons that represent a particular word."
This long statement really says nothing at all other than vaguely claiming that some type of activation is going on, claiming that some type of circuits are involved, and claiming that some neurons represent a word. But how could neurons conceivably represent a word? We can imagine no combination of neurons that would represent the word “freedom” or “religion” or “eternity” or “proficiency.” And if there were such a set of neurons somehow storing the meaning of a word, how could my brain ever instantly find that exact tiny set of neurons instantly, as soon as I heard that word? Our author provides no answers.
Since electricity passes around between in the brain, the brain can be conceived rather loosely as a huge collection of circuits. But we don't do anything to explain instant memory retrieval by saying it “is accomplished by circuits,” just as we don't explain something going on in your smartphone or computer by vaguely saying that it is “accomplished by circuits” or “accomplished by components” or “accomplished by electrons.”
We then have Paul Michael Guinther PhD state this: “Asking how the brain in some way causes the retrieval of memories involves a lot of metaphor ...and therefore isn't really answerable in any kind of scientifically meaningful way.” This is followed by a long answer from a “Deleted Profile” user who doesn't cast much light on this question.
We then have additional comments by Graeme Smith, who has no credentials in this area, He states the following:
"Output comes in the form of release of neurotransmitters, and in some rare cases actual electric contact between cells. ...A great amount of the storage and retrieval of memories has to be thought of as interpretation of the signals to retrieve the sense of them despite the processing steps taken at the same time as the storage steps. ...Different areas of the Cortex are interpreted differently especially the modal areas which take the inputs from specific sensory zones, and analyse it according to the mode of sensory input those sensory zones respond to. At different stages in the memory different areas in the cortex are activated resulting in processing of different types of outputs. The architecture of the brain, and micro-structure of the tissues, act together to guide information of a specific type through processes of a particular type, to other areas of the brain forming networks that process the information in a pattern that is similar across the brain."
This very much sounds like the talk of someone who does not understand how a brain could retrieve a memory, and who is just tossing around a few vague phrases, hoping that it sounds like something resembling understanding.
We then have an answer from the authority Dorian Aur of the Department of Comparative Medicine at Stanford University. Aur claims, “Fragments of memory are written inside neurons and synapses within molecular structure.” There is no real evidence that this is true. There is no evidence of any information-writing capability in the brain, nothing like the write head of a disk drive. No one has a coherent detailed theory as to how learned knowledge or episodic memories could be translated into neural states. We know that the proteins that make up synapses are very short-lived, having average lifetimes of only a few weeks. There is no workable theory as to how a brain could store memories lasting for decades.
Aur then states, “These structures vibrate and generate a broad electromagnetic spectrum,” and says, “In computational terms, meaningful fragments of information which are stored inside the structure are read out.” This isn't really saying anything. Aur doesn't give an answer to the question or an explanation, other than claiming memories are written and read.
There then follows a long passage by Graeme Smith, who talks about electrical signals crossing synapses gaps, and the artificially produced effect called LTP. This provides nothing to clarify how a brain could instantly find a memory and load it into your mind so that you thought of that memory.
So this finishes my look at the 68 answers the experts have given to the basic question, “How Are Memories Retrieved in the Brain?” I have quoted all the best answers. The answers run to a total of about 8000 words. But the experts provide no real insight as to how a brain could instantly retrieve a memory. The authors toss around their erudition in various ways without any answers to the basic questions. There seems to be an awful lot of “just faking it” kind of verbiage, the type of empty phraseology and gobbledygook that people use when trying to persuade you that they understand something that they don't. None of the main problems are answered, and some of the main problems are not even mentioned.
None of the authors offers anything like a theory as to how instant memory retrieval could occur. The authors speak as if they were completely ignorant of this difficulty. None of them seems to be aware that explaining how a brain could find a memory instantly is 1000 times harder than explaining how a brain could find a memory if it has hours or days to scan though memories stored in it.
None of the authors suggests anything like a theory as to how a brain could read encoded information stored in it, translating that into a thought. The authors don't even offer a suggestion as to some neural effect that could act like a read mechanism.
Quite a few of the people offering answers are guilty of what we may call jargon bluffing, which is what goes on when someone offers dense, jargon-laden prose trying to make you think that he understands something he does not at all understand. Below is an imaginary example of this type of prose, which sounds like quite a few of the answers that are found on this page:
"The remembrance phenomenon is produced by a complex symphony of interlocking reciprocal causal factors. Neurotransmitters, circuits, specific synapses and highly specialized neural components all play specific roles in the intricate functionality. We are beginning to unravel the mechanistic specificity that evokes what we experience as a distinct recollection event. A distinct repertoire of biochemical events involving diverse interconnected cells may elicit a vivid reminiscence."
A statement like this is just bluffing, and neither shows any understanding of how a brain could retrieve a memory, nor does it describe any real theory as to how such a thing could occur. We should not be impressed at all by this type of empty verbiage, which is found all over the place on the web page I am discussing.
But two or three of the writers have spoken honestly and candidly by confessing (in one way or another) that they do not understand how a brain could retrieve a memory. We get some similar candor in a recent book Why Only Us? Language and Evolution by the leading linguist Noam Chomsky and Professor Robert C. Berwick. Here is an excerpt (pages 50-51):
"The very first thing that any computer scientist would want to know about a computer is how it writes to memory and reads from memory....Yet we do not really know how this most foundational element of computation is implemented in the brain."
The complete lack of any workable theory for how memory recall can occur so quickly is admitted by neuroscientist David Eagleman, who states the following:
"Memory retrieval is even more mysterious than storage. When I ask if you know Alex Ritchie, the answer is immediately obvious to you, and there is no good theory to explain how memory retrieval can happen so quickly."
I offer this ResearchGate.net web page as Exhibit A that modern neuroscientists have no understanding at all as to how a brain could instantly retrieve a memory. The lack of any credible theory of how instantaneous memory retrieval could occur is one of the major reasons for rejecting the claim that the brain stores memories. Many other such reasons are discussed at this site.
On the "How Stuff Works" site, which often has pretentious and dogmatic answers in which writers pretend to understand things they don't understand, we have a five-page answer with the title "How Human Memory Works." The author is the neuroscientist Richard C. Mohs. Engaging in speculation for which he provides no references, evidence or citations, Mohs states the following:
"Each part of the memory of what a 'pen' is comes from a different region of the brain. The entire image of 'pen' is actively reconstructed by the brain from many different areas. Neurologists are only beginning to understand how the parts are reassembled into a coherent whole."
The last sentence gives away that Mohs isn't actually referring to something that is known here, and we have no actual evidence that such a claim is true. If Mohs' speculation were true, it would make it many times harder to explain a memory retrieval -- for explaining instantaneous retrieval from "many different areas" would be harder than explaining instantaneous retrieval from a single area.
At the end of the first page, Mohs promises, "On the next page, you'll learn how encoding works and the brain activity involved in retrieving a memory." But the pages that follow do nothing to explain such things. The page entitled "Memory encoding" does nothing to explain how a brain could possibly translate conceptual knowledge or episodic memories into neural states, a gigantic unsolved difficulty as great as the difficulty of explaining memory recall. No neuroscientist has a coherent detailed theory on this matter, and Mohs certainly does not state one. On the page entitled "Memory Retrieval," Mohs writes about 500 words that do nothing to explain how such a thing could occur in the brain. He presents no theory and no speculation, and says nothing specific about the brain.
Our neuroscientists do not understand how a brain could encode a memory, do not understand how a brain could instantly retrieve a memory, and do not understand how a brain could store a memory for decades despite rapid protein turnover in synapses which should prevent stored memories from lasting in synapses for even as long as a month. If a neuroscientist ever gives you the impression he understands such things, it's a sham or a bluff, or a case of self-deception in which someone has deluded himself into thinking he understands something he doesn't.
This morning I had a good example of the type of memory recall that is inexplicable through any theory of neural recall. Turning to the TCM channel, I saw for the first time the 1951 movie The People Against O'Hara. The movie was in its middle, and there was a scene in which a witness delivered testimony. Looking at the actor, I instantly identified him as the little-known actor William Campbell. But I had only seen William Campbell in two other movies or TV shows, those being two Star Trek episodes made in 1967. I was able to instantly identify him even though he looked 16 years younger than I had ever seen him, and even though I should have by all rights forgot his name (a name I cannot recall thinking about, reading about or hearing about in the thirty years previous to today). No one will ever be able to explain how such instantaneous recollection of very obscure memories (not accessed in decades) could occur if memories are stored in the brain.
Modern biology word-cloud
No comments:
Post a Comment