- "Direct evidence that synaptic plasticity is the actual cellular mechanism for human learning and memory is lacking." -- 3 scientists, "Synaptic plasticity in human cortical circuits: cellular mechanisms of learning and memory in the human brain?"
- "The fundamental problem is that we don't really know where or how thoughts are stored in the brain. We can't read thoughts if we don't understand the neuroscience behind them." -- Juan Alvaro Gallego, neuroscientist.
- "The search for the neuroanatomical locus of semantic memory has simultaneously led us nowhere and everywhere. There is no compelling evidence that any one brain region plays a dedicated and privileged role in the representation or retrieval of all sorts of semantic knowledge." Psychologist Sharon L. Thompson-Schill, "Neuroimaging studies of semantic memory: inferring 'how' from 'where' ".
- "How the brain stores and retrieves memories is an important unsolved problem in neuroscience." --Achint Kumar, "A Model For Hierarchical Memory Storage in Piriform Cortex."
- "We are still far from identifying the 'double helix' of memory—if one even exists. We do not have a clear idea of how long-term, specific information may be stored in the brain, into separate engrams that can be reactivated when relevant." -- Two scientists, "Understanding the physical basis of memory: Molecular mechanisms of the engram."
- "There is no chain of reasonable inferences by means of which our present, albeit highly imperfect, view of the functional organization of the brain can be reconciled with the possibility of its acquiring, storing and retrieving nervous information by encoding such information in molecules of nucleic acid or protein." -- Molecular geneticist G. S. Stent, quoted in the paper here.
- "Up to this point, we still don’t understand how we maintain memories in our brains for up to our entire lifetimes.” --neuroscientist Sakina Palida.
- "The available evidence makes it extremely unlikely that synapses are the site of long-term memory storage for representational content (i.e., memory for 'facts'’ about quantities like space, time, and number)." --Samuel J. Gershman, "The molecular memory code and synaptic plasticity: A synthesis."
- "Synapses are signal conductors, not symbols. They do not stand for anything. They convey information bearing signals between neurons, but they do not themselves convey information forward in time, as does, for example, a gene or a register in computer memory. No specifiable fact about the animal’s experience can be read off from the synapses that have been altered by that experience.” -- Two scientists, "Locating the engram: Should we look for plastic synapses or information- storing molecules?
- " If I wanted to transfer my memories into a machine, I would need to know what my memories are made of. But nobody knows." -- neuroscientist Guillaume Thierry (link).
- "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." -- Neuroscientist David Eagleman.
- "How could that encoded information be retrieved and transcribed from the enduring structure into the transient signals that carry that same information to the computational machinery that acts on the information?....In the voluminous contemporary literature on the neurobiology of memory, there is no discussion of these questions." --- Neuroscientists C. R. Gallistel and Adam Philip King, "Memory and the Computational Brain: Why Cognitive Science Will Transform Neuroscience," preface.
- "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." -- Noam Chomsky and Robert C. Berwick, "Why Only Us? Language and Evolution," page 50.
- "When we are looking for a mechanism that implements a read/write memory in the nervous system, looking at synaptic strength and connectivity patterns might be misleading for many reasons...Tentative evidence for the (classical) cognitive scientists' reservations toward the synapse as the locus of memory in the brain has accumulated....Changes in synaptic strength are not directly related to storage of new information in memory....The rate of synaptic turnover in absence of learning is actually so high that the newly formed connections (which supposedly encode the new memory) will have vanished in due time. It is worth noticing that these findings actually are to be expected when considering that synapses are made of proteins which are generally known to have a short lifetime...Synapses have been found to be constantly turning over in all parts of cortex that have been examined using two-photon microscopy so far...The synapse is probably an ill fit when looking for a basic memory mechanism in the nervous system." -- Scientist Patrick C. Trettenbrein, "The Demise of the Synapse As the Locus of Memory: A Looming Paradigm Shift? (link).
- "Most neuroscientists believe that memories are encoded by changing the strength of synaptic connections between neurons....Nevertheless, the question of whether memories are stored locally at synapses remains a point of contention. Some cognitive neuroscientists have argued that for the brain to work as a computational device, it must have the equivalent of a read/write memory and the synapse is far too complex to serve this purpose (Gaallistel and King, 2009; Trettenbrein, 2016). While it is conceptually simple for computers to store synaptic weights digitally using their read/write capabilities during deep learning, for biological systems no realistic biological mechanism has yet been proposed, or in my opinion could be envisioned, that would decode symbolic information in a series of molecular switches (Gaallistel and King, 2009) and then transform this information into specific synaptic weights." -- Neuroscientist Wayne S. Sossin (link).
- "We take up the question that will have been pressing on the minds of many readers ever since it became clear that we are profoundly skeptical about the hypothesis that the physical basis of memory is some form of synaptic plasticity, the only hypothesis that has ever been seriously considered by the neuroscience community. The obvious question is: Well, if it’s not synaptic plasticity, what is it? Here, we refuse to be drawn. We do not think we know what the mechanism of an addressable read/write memory is, and we have no faith in our ability to conjecture a correct answer." -- Neuroscientists C. R. Gallistel and Adam Philip King, "Memory and the Computational Brain Why Cognitive Science Will Transform Neuroscience." page Xvi (preface).
- "Current theories of synaptic plasticity and network activity cannot explain learning, memory, and cognition." -- Neuroscientist Hessameddin Akhlaghpourƚ (link).
- "We don’t know how the brain stores anything, let alone words." -- Scientists David Poeppel and, William Idsardi, 2022 (link).
- "If we believe that memories are made of patterns of synaptic connections sculpted by experience, and if we know, behaviorally, that motor memories last a lifetime, then how can we explain the fact that individual synaptic spines are constantly turning over and that aggregate synaptic strengths are constantly fluctuating? How can the memories outlast their putative constitutive components?" --Neuroscientists Emilio Bizzi and Robert Ajemian (link).
- "After more than 70 years of research efforts by cognitive psychologists and neuroscientists, the question of where memory information is stored in the brain remains unresolved." -- Psychologist James Tee and engineering expert Desmond P. Taylor, "Where Is Memory Information Stored in the Brain?"
- "There is no such thing as encoding a perception...There is no such thing as a neural code...Nothing that one might find in the brain could possibly be a representation of the fact that one was told that Hastings was fought in 1066." -- M. R. Bennett, Professor of Physiology at the University of Sydney (link).
- "No sense has been given to the idea of encoding or representing factual information in the neurons and synapses of the brain." -- M. R. Bennett, Professor of Physiology at the University of Sydney (link).
- "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." --Neuroscientist C.R. Gallistel, "The Physical Basis of Memory," 2021.
- "To name but a few examples, the formation of memories and the basis of conscious perception, crossing the threshold of awareness, the interplay of electrical and molecular-biochemical mechanisms of signal transduction at synapses, the role of glial cells in signal transduction and metabolism, the role of different brain states in the life-long reorganization of the synaptic structure or the mechanism of how cell assemblies generate a concrete cognitive function are all important processes that remain to be characterized." -- "The coming decade of digital brain research, a 2023 paper co-authored by more than 100 neuroscientists, one confessing scientists don't understand how a brain could store memories.
- "The human brain isn’t really empty, of course. But it does not contain most of the things people think it does – not even simple things such as ‘memories’....We don’t create representations of visual stimuli, store them in a short-term memory buffer, and then transfer the representation into a long-term memory device. We don’t retrieve information or images or words from memory registers. Computers do all of these things, but organisms do not." -- Robert Epstein, senior research psychologist, "The Empty Brain."
Every additional piece of evidence establishing extraordinary human memory abilities is an additional nail in the coffin of the doctrine that brains store memories. Given a brain lacking any of the characteristics that would be required to allow the best examples of human memory performance, the credibility of the claim that brains store memories is inversely proportional to the highest observed speed, accuracy, duration and depth of human memory performance. The longer humans can remember things and the more they can remember and the better they can remember and the more quickly they can remember and the more quickly they can form new memories, the less credible are claims of brain memory creation and storage.
Let us look at some clips from newspaper accounts of marvels of human memory. Below is a 1921 account of a memory marvel:
Below is a news story from 1922:
George Vogan de Arrezo memorized the entire text of Virgil's Aeneid (consisting of 9,896 lines). Aitken and JB performed similar feats when they memorized epic poems of about 10,000 lines. According to an old newspaper account, Leste May Williams memorized 12,000 verses of the Bible, including the entire New Testament. The New Testament has about 180,000 words, so the feat of Leste May Williams would seem to be far more impressive than the memorization of Virgil's Aeneid, which has only 63,719 words. The same feat of memorizing the New Testament was achieved by a male minister (Henry M. Halley).
As a reader of your blog would i like to hear your opinion to the following article https://www.nature.com/articles/s41586-024-07558-y
ReplyDeleteIt's a study mapping a fruit fly brain. The study should have had a title referrring to a fruit fly brain,
ReplyDeleterather than having a title referring to an "adult brain," which most people would think was a human brain.
The study is mainly low-level detail work. It includes a hedging weak claim that "Tracing from a subset of photoreceptors
to descending motor pathways illustrates how structure can uncover putative circuit mechanisms underlying sensorimotor behaviours."
But nothing is done to show a neural basis for behavior of the fruit fly. The paper includes the untrue claim that
"The resulting wiring diagrams of neural circuits have provided crucial insights into how the brain generates social, memory-related or navigation behaviours."
It provides no data backing up that claim. There are only a few references to memory, just a few passing references, nothing substantive.
Below is a quote from a BBC article on that fruit fly study: "Dr Gregory Jefferis, of the Medical Research Council's Laboratory of Molecular Biology (LMB) in Cambridge told BBC News that currently we have no idea how the network of brain cells in each of our heads enables us to interact with each other and the world around us."
ReplyDeletehttps://www.bbc.com/news/articles/c0lw0nxw71po