Greg Miller " Many details of the process of memory recall are not known (or are disputed). Even so, some researchers say it's time to revise some aspects of the standard view—such as the notion that the hippocampus is not involved in retrieving older episodic memories, and that memories become fixed and unchangeable once transferred to the neocortex. Newer work suggests a far more fluid role of memory, and one in which retrieval plays a crucial role in shaping memory over time"
Hi Mohammed, one interesting issue in this context is the dualism between physical storage in neurons, like we are used to in silicon for computational data, and storage as a process that is involved in cognition and is related with neuropsychological processes. The belief that knowledge is always incremental suggests that knew knowledge doesn't correspond to new allocation of neurons but on the establishment of new connections (or both as i would defend). That i think is aligned with the episodic memory from Miller where an episode would be a cluster of records in a given time.
I have no doubts at all that the mechanisms controlling retrieval are a collaborating team of high-level cognitive, affective and motorically-influenced & 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. Fernando L-F's (and Miller's) models fit into this account perfectly, I think.
Well, this is a quite extensive area, and there are several areas/angles from which one can/should look at this. There is the aspect of "storing" information, well as humans we retrieve a lot of information during the day time, and at night (so when we sleep) we filter through all the information of the day and "store" it in our neuron network. There is a need to do this repetitively, so hence the fact that we need to go through something multiple times when studying to be able to retain it in our brain (some people more others less, but it is the same principle that applies). From my understanding, the actual "storage" is not making use of address values or so like CMOS memory, but is fully associative, so we store information that "relates" to one another. This can be best understood through the following example: if you were to answer the question: what did you do on 08/12/2014, you would struggle to tell straight away, without going to your diary and looking for some hint on what you may have done. However, if you were asked the question, what did you do the last time you went to the beach, you would be able to straight away start telling a full story.
Personally, I don't have an immediate answer to the retrieving of "old" data, but I guess some of the answers need to be found in studying brain diseases where we are no longer "remembering" anything, and there may be a relation with the fact that we never fully use all of our brain, so does that evolve over time ?
Mohammed,
The very notion of 'retrieval' assumes that some part of the brain is like a library, a filing cabinet or a hard drive, just packed with indexed data with addresses. I am not a neuroscientist, but I would be very wary of implicitly adopting a theoretical paradigm which will constrain the kinds of questions you can ask, let alone the kinds of answers you can get. I do not have a solid counter theory, but I have a strong sense that this notion, like other cognitvist and functionalist notions, is simply wrong.
dear mohammed,
i think that today neuroscientists are less holding on that memory is stored in a "location" in the brain similar to a "hard drive"... but there are parallel fields that refer to memory in a different angles that i think they are all true: the first one rely on biochemical signaling for storing data.. rising from the assumption that long term memory must have protien synthesis (protein synthesis inhibitors as rapamycin/anisomysin prevent memory storage) and that short term memory rolled by synaptic plasticity. another approach go further and say that memory items are stored in the strength of connections between neurons. i believe that for each situation (motor memory, Declarative memory (emotional/ or not) etc.) there is a pattern of memory storage (different mechanisms), and therefor the retrieval is different.
Best,
Salman
Maybe some of you might like my ideas on this question.
Just have a look! You don't even have to leave RG!
http://dx.doi.org/10.13140/2.1.1087.2009
Dear Herwig..Brings to mind a quote from C.S. Lewis " and the Dodo bird announced " everybody has won, so all shall have prizes".
And also the discussion regarding place cells https://www.researchgate.net/post/Place_cells_What_does_it_prove
Part of the problem with dealing with memory retrieval, is that a good percentage of our brain has memories that are not directly retrievable. This IMPLICIT memory makes up a background to the more retrievable EXPLICIT memory that we expect from our experience with computers etc. Part of my work has been characterizing this implicit memory and understanding how it becomes explicit. It is a complex system that is based on the very real assumption that neural networks do not lend themselves directly to explicit memory, and a new architecture is required to achieve that state.
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. In recalling this experience, hippocampus does not participate again. In recalling this experience the brain will ask the neural components that firstly participate in processing this experience in the level of uniassociation or multiassociation cortex.
Sutarmo, while nothing you say is wrong, there is a lot of detail being glossed over in this high level description. Things generally do not work that simply.
Why some one want to recall something? I think she or he has an idea to get an answer. This idea may a word or something that must be associated to something in the memory. It needs a process, for example a phonological process and semantic retrieval. The main process is associating the idea with a proper thing/things in the memory that is in the level of association cortex.
While what you say is true, There are two types of cortical tissues, allocortical, and isocortical tissues, and how you retrieve something from allocortical tissues, is just one mode of retrieval from isocortical tissues. The Association Cortexes are all isocortical tissues. Some of which are granular and some are not. Without understanding how the neural networks that make up the tissues react your description is glossing over some important aspects to retrieval. Details that completely change the way that information must flow.
Graeme,
while nothing you say is wrong, Sutarmo is seeing the 'picture' in much more detail with much higher resolution. All parts of the brain are involved in building up memory, so all parts are involved in retrieving it. 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.
Sutarmo,
I would be very much interested to get just a brief response to my paper from you. You will not need to spend more than 10 min to judge if you like my metaphors or not.
http://dx.doi.org/10.13140/2.1.1087.2009
Ursula
Herwig,
What do YOU think about my metaphors? On principle, I might be able to help constructing a potential benefit for patients with diseases connected with the loss of white matter (PD, HD, MS). For me white matter is an important part of the memory and its retrieval. As soon as white matter is destroyed, memory will be destroyed. All rhythms of the brain will be destroyed parallel to the destruction of white matter. EEG signals are best indicators, as to my view.
It is a dream of mine to find an expert as interlocutor. I downloaded your paper on Huntington’s Disease, Udo Rüb et al. (2014). This could be a starting point. Since this question might not be of common interest, just contact me in parallel if you like.
Ursula
I am sorry Ursula. I must get the definition of holography before I can answer or to give comments to your questions. What I know is, all process in the brain and almost in all part of the body are biochemical and bioelectrical process. Even the smallest activity in the body need an opening of sodium channels, calcium channels and other biochemical and bioelectrical process. But I still can not catch what is the holographic process of memory. May be I must read another paper. I am very sorry. Thank you for your exciting comment to me.
Sutarmo,
Thank you very much for your feedback.
You say: “Even the smallest activity in the body need an opening of sodium channels, calcium channels and other biochemical and bioelectrical process.” I fully agree with this! Without the slightest constraint! Maybe you start reading my essay somewhere in the middle. Maybe on p. 19 “Autowaves – non-classical waves” and “How can we adapt the above considerations to the brain?”
What I want to say is that all these “small activities” are induced by or at least connected with different kinds of biochemical and bioelectrical waves and oscillations, Ca2+-waves, Ca-dependent enzyme waves and oscillations, action potentials are waves also, etc. Holography is a possible way of storing and retrieving coherent waves and oscillations to reestablish the brain’s state on different oscillatory levels.
I am aware of the fact that I am “putting the car before the horse” to some extent. But I am not able to find the backside of the horse! Holography is my “historical” approach to the subject. And it is the metaphor I am most familiar with. Self-organization of brain waves and oscillations might be a much better starting point. But this is still “black ice” for me. I would be much more vulnerable! With using holography as a metaphor I am emphasizing that there might be a way to store and retrieve all those waves and oscillations which “cause” these small activities or are at least observed in connection with them.
Ursula
Ursula, I believe both you and Sutarmo are missing the nature of neural networks and the limitations they impose upon the memory.
Graeme,
The network is a network of oscillators that are able to resonate. It is build by biomolecules, amino acids, nucleic acids, gens, proteins, cells, ion channels, ion pumps, synapses, axons, dendrites, white matter with Ranvier nodes, etc, etc. There is no computer in the brain. It is an oscillatory network only, as it seem to me!
Ursula
Ursula, Neurons are cells first and foremost, they connect making links between them, and by this chemical/biological method, transfer signals between them. Only then does the network seem to have the characteristics you propose.
I never said the brain had a computer in it, that is YOUR interpretation.
However it is not just an oscillatory network, It actually stores and retrieves data.
It stores it in synaptic connections, and in Chemical Mechanisms that help decide where new synaptic connections will form.
Graeme,
I have no idea what “really” is “the case”, I do not know the “truth”, whatsoever.
But as it seems to me: There is no information besides waves and oscillations reaching the brain’s sensory system. Information is created within the brain, caused to coincident resonances (linkage of resonating ‘devices’ during input processing). And these waves and oscillations from the outside world (light, sound, heat, …) cause reactions of the brain tissue. They stipulates and ‘enslaves’ all kinds of possible brain-waves and oscillations. That means, all reactions of the brain to the input w+o are processed in form of brain-waves and oscillations again. (E.g., already chemical binding is caused by and causes electromagnetic oscillations, usually in the infrared part of the spectrum.) If we could repeat his waves and oscillations in a similar way, they might cause the same reactions as the original w+o. Reminds to memory, doesn’t it?
In the case of normal photography, it is the photoemulsion that stores and allows to retrieve the light-waves reaching the film. And the pictures we take, are retrieved by normal light. In case of optical holography, the phases of the (laser) light waves are stored in addition. But the photopaper (photoemulsion) is quite the same. Now I am searching for the analogy of the photoemulsion in the brain. (There are a manyfold of analogies!) The characteristic feature of laser light is its coherence, not more and not less. As it seems to me, we observe coherent w+o in the brain. That’s what I call the ‘laser in the brain’. The processes that cause coherence are described as self-organization of brain w+o, analog to the generation of laser light. (See Hermann Haken, ref. in my essay.)
Ursula
Ursula
I ever think that neurons work like an electronic component. Some circuit of neuron can function as a transmitter or receiver like in a television or radio. Some time an invidu can transmit a message to other like in telepathy. And I still think that the brain is a super computer.
Also, all activity in the brain can be detected as an electrical wave. And the manifestation oft all biochemical process are in the form of bioelectrical wave.
Sutarmo,
Do you have any idea how to improve my descriptions? Enhancements are most welcomed!
At present, I am trying to learn more about the metaphors "Information", “Entropy”, “Energy”, and “Self-organization” in connection with biological matter and processes by reading Manfred Eigen’s wonderful book “From Strange Simplicity to Complex Familiarity – A Treatise on Matter, Information Life and Thought”, (2013)
Maybe, eventually I will be able “to put the car on the back of the horse”.
Ursula
I am sorry. I already downloaded your paper, but I could not find it. Would you like to give me ones more? And I can not find Nanfred book.
Sutarmo
Manfred Eigen's book:
http://www.amazon.com/gp/product/019857021X/ref=pe_375270_129734910_em_1p_0_ti
Ursula, Waves do not come out of nothing, they are formed, and in the brain they are formed by micro-potentials aggregated out of the firing of neurons. It is not resonance that determines what the waves are, but the activation of the neurons. As a result, Brain waves are not sinusoidal, but represent the aggregation of multiple single potentials, being mere vibrations that are filterable through various filters as if they were sinusoidal waves.
While we may be unsure why there are certain frequencies that are louder than others, it is probably not resonance that makes them that way. If it were resonance, the louder frequencies would be the natural harmonics of the original waves which they are not.
Instead they seem centered around certain filters and not around others which suggests that they have an incidental rather than resonant frequency. It does not matter how it seems to you, your metaphors are mistaken.
Graeme,
I am always surprised when people can feel so sure! But I grant it to you! I am missing such an internal security!
As I learned from Fourier, all wave and oscillations – even action potentials – can be transformed in a series of harmonic waves, not only mathematically but also physically. That is what defines spectrometers. In the brain we might find (as it seems to me) a multitude of biomolecular structures which can act as spectrometers. They pick up those frequencies with which they can resonate.
What the resonances are concerned, I would like to refer on my essay where I discussed this issue in great detail. If you are really interested in a discussion with me then please read my essay first. It is too time consuming for me to repeat all that stuff I struggled with in my essay. Hope this doesn’t sound too impolite. It should not!
Ursula
Ursula, the brain is not resonant at many of the frequencies it produces. For instance Gamma waves which are associated with consciousness are not resonated, they are enforced by transmission of the signals to produce the waves via the Reticular Activation System. There are actually neurons all over the brain that are activated by this network of timing signals, and in turn produce a frequency that resonates with our detection circuits. If they were resonated then they naturally would produce harmonics at 20 and 80 hertz and would resonate in a narrow band instead of spreading themselves across a broad band that is only approximately 40 hertz.
The reason I am sure about this, is I understand the science behind the EEG signals, have seen the waveforms that are produced even in my own EEG trace, and have Looked carefully at the EEG device to see how it works. While the brain radiates at certain frequencies, such as the gamma frequency mentioned, a strict fourier transform of the signal would include more frequencies than a sinusoidal wave at the titular frequency, and the frequency mix would change more often, and be less constant than such a base frequency. This is because it is not a pure 40 hertz signal as suggested by the filter that is used to detect it, but an aggregation of other signals that tends to cluster around the 40 hertz frequency.
Actually Ursula, I am not interested in having a discussion with you, you bring nothing new to the table that interests me. I only defend against some of the misconceptions that you seem interested in pushing on the group. Such as the idea that the reason that the brain radiates certain frequencies has purely to do with resonance. The Reticular Activation System would not need to exist if this were the case.
Graeme,
It would be great if we could be “friends”! I am urgently looking for a genuine EEG experts! I am none! I am a physicist and all what I know about the brain, I learned from textbooks and scientific papers. EEGs play an important role in my hypothesis. And so does the Reticular Activation System! The RAS is THE plain player in the concert of the endogenous brain rhythms, as it seems to me. If it seems to you too, I would be really happy!
Maybe our problem is a “language” problem. You say about Gamma waves that they “are enforced” by transmission of the signals to produce the waves via the Reticular Activation System and neurons all over the brain … “are activated”. I am saying they “resonate” with the RAS signals. I am sure that means the same. I am using the metaphor “enslaved” sometimes. Resonance means that there are waves and oscillations that “enforce” or “activate” oscillating systems by activating their eigenfrequencies. Oscillating systems can be "enforced" or "activated" only by their activating their eigenfrequencies. And this is called “resonance”.
In my hypotheses the RAS is playing an essential part giving or at least contributing to a “coherent background” which is required to interfere with the input waves and oscillations. What you wrote is “water on my mills”!
Believe me, I am not interested at all in “pushing some misconceptions on the group”. For heavens sake! I would like to transform my hypothesis to what the experts – like you – observe! I am discussing on RG because I am looking for experts!
A question to you as an expert: Are EEG signals waves or oscillations? What would you say? As far as I know you measure oscillations on the scalp, but as far as I also know, oscillations resonate with = activate their next neighbors, so that waves are produced. (Which you normally don’t measure on the scalp!?)
Ursula
Ursula, the Eigenfrequencies are the harmonic frequencies, I just noted that there is no support for harmonics in the EEG. In the event of gamma frequencies signals that are repeated multiple times in the same period affect the habituation of the neuron. In other words signals arrive at the neuron, and chemical systems react to the period of the signals, if the period is short enough habituation is reduced. The RAS supplies signals with a certain period, to a certain synapse on the cell, and as a result increases the length of time that a neuron can fire, before it starts to run out of Calcium at the axion bouton. That there is a calcium wave when the cell first absorbs calcium then releases it, has no direct relation to the RAS signal, it just links to it chemically and biologically.
In other words it is not a resonance at all but a process that has at least two separate steps, first the RAS sends a signal then in response to that signal calcium is absorbed and released, which causes a calcium wave. The important step is the result of that calcium reaching the axion bouton and releasing more neurotransmitter not the incidental fact that calcium waves are at gamma wave frequencies. There is a distinct latency that represents the activation of the synapse between the RAS signal and the Calcium Wave.
Believe me I am by no means considered an Expert on EEG, but I can tell when a problem occurs in the "Resonance" assumption you have made.
I think the processes in the brain have no correlation with electromagnetic wave.
The brain is able to translate between a variety
of types of representations and probably makes
use of this ability. Oscillations are a means
of recruiting the masses. The blinking of a single
firefly is unseen but not thousands in a shrubbery.
Some studies that put memory and oscillations
into relationship:
http://www.jneurosci.org/content/34/22/7587
http://www.eurekalert.org/pub_releases/2012-11/niom-ibw110212.php
http://medicalxpress.com/news/2012-01-short-term-memory-based-synchronized-brain.html
http://datam.i2r.a-star.edu.sg/papers/2012_CNS_CA3.pdf
http://www.eurekalert.org/pub_releases/2010-03/cmc-aom032210.php
http://ucsdnews.ucsd.edu/archive/newsrel/science/04-26-11neuralpacemakers.asp
http://www.redorbit.com/news/science/2063515/brain_state_affects_memory_recall/
http://www.eurekalert.org/pub_releases/2012-11/miot-bwe112012.php
http://www.eurekalert.org/pub_releases/2004-05/asu-aac051004.php
Regards,
Joachim
There is a theory and book by William H. Calvin,
"The Cerebral Code" ("Die Sprache des Gehirns").
The basic idea, as I understand it, is:
on the cortex, a 2D organ, waves are transmitted
in time and 2D space. Neurons catch a certain periodic
excitation pattern, what they hear from their
surrounding, and every now and then repeat it.
Especially if it is one with big amplitudes. If two
excitation centers in the right distance
are in synchrony, they are able to "recruit"
neurons in a certain distance to repeat
that pattern. A triangle forms. After a
while, the whole cortex is seeded with triangles
of neurons (columns) in synchrony, all firing
in the same tune. In my understanding, this
might be the neural basis for representing
symbols (among other possibilities like
grandmother neurons or binary codes).
http://williamcalvin.com/bk9/bk9ch3.htm
http://williamcalvin.com/socns94.html
Related work is BRAINN by Rafal Bogacz and
Christophe Giraud-Carrier.
http://dml.cs.byu.edu/~cgc/pubs/NC1998.pdf
Maybe also of interest: single neurons
are able to detect sequences.
http://www.eurekalert.org/pub_releases/2010-08/ucl-snc081110.php
Regards,
Joachim
You might start by discarding the colloquial metaphor, supported by1950s computer models, that memories are "retrieved." They are activated, not retrieved. After that, the answer could fill a book.
John,
My mother tongue is German. Would you be so kind to explain me the difference between 'retrieved' and 'activated'? Could I say "memory is retrieved by activation?
Ursula
John, There are two separate modes of Access for memories, both based on Activation, the Content Accessible, and Place-Code accessible memories as suggested by Marr (1970) Neural networks do not easily loan themselves to place code accessible architectures, so it requires a few major architectural changes to allow the Neural Networks to "Retrieve" Memories in a place-code accessible form. But evidence suggests that Isocortical tissues have enough of an architectural difference that with some extra architectural factors they can convert the usual Content-Accessible memories to something resembling a place-code accessible form. So for these columns in the cortex both content accessibility and place-code accessibility are possible.
John,
thankyou, I endorse your response and the spirit of it. Today, in another thread I said:
Velina, and Richard,
I count myself only as a relatively well, but broadly, informed dilettante in your field. My question - which I often have to ask disciplinary specialists - is about the dangers of operational metaphors and axiomatic assumptions. I believe I know the origins of the bottom up and top down terminology. I am dubious about metaphors applied to brain/mind. Metaphors, generally, are useful until they are not. But the point at which they become not-useful - and take researchers down what transpire to be blind alleys - is usually unclear. Until there is some kind of Kuhnian shift. And then it all seems obvious.
When such metaphors become institutionalised - when grants and degrees and departments become structured around them - it can be very difficult for an embedded researcher to even conceive of questions which are impossible to ask within the disciplinary - or subdisciplinary -paradigm.
I mean no disrespect to you, I know from direct experience as well as literature, that such questioning can appear incomprehensible, or offensive. But even if researchers feel that they are pursuing objective knowledge through experimentation, all research programs (I think) rest on some theory, some set of axioms, which by definition are untestable. So at the root of this fact finding is belief. I suppose this has to be, but I think it is a reality we all ought to be vigilant about, and so must continually try to ask 'out of the box' questions, in order to test those underlying assumptions.
Simon Penny
Ursula, Graeme, & Simon, Take word recognition for an e.g., where visual patterns such as line and angles,...letter features,.. letters,.. letter sets,.. and lexical words are "recognized" in a left temporal visual word form area where individual words are represented by clusters of neurons. Lexical learning and lexical word recognition is easily modeled by neural networks that may be mapped onto cortical locations - see O'Reilly's "emergent "on the web. All of the networks have recurrent bottom-up, top-down and lateral neural connections. 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., pitorial resprentation, 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 of suppress the activation of the neurons that represent a particular word. The "memory" - another metaphor is widely distributed. Ursula, the problem with the "retrieval" metaphor is that it implies moving a word's representation from one place to another, as in a computer. But the brain doesn't do that. Simon. Scientists may have great confidence in a model, but they don't "believe." They create models that best represent all that they have observed and conjectured, and try to get more evidence that will allow they to replace today's model in favor of a better one in a few months. It's all a work in progress.
John,
I can't really comprehend your caveat what the verb "retrieve" is concerned since I am no computer scientist. But I will avoid it in the future. Other neuroscientists might think or feel as you.
How about using "to reconstruct" memory?
Ursula
"Simon. Scientists may have great confidence in a model, but they don't "believe.""
John, scientists used to believe in phlogiston and ether (etc). Psychoanalysts used to believe in hysteria and neuraesthenia. I believe in gravity and in electrons and for that matter, Einsteinian relativity. But Einstein did not *believe * god played dice with the universe. Some scientists believe in the possibility of objective knowledge. I'm being a bit provocative here, but I do think the distinction between 'belief' and confidence in a model' is a little hazy.
Simon
The idea of memories as being real "things" with existential status is just part of a computer metaphor. It's like asking a Freudian how hydraulics suppress memories; don't take it too literally. Furthermore, the idea that memories exist is not falsifiable, since it is literally not possible to demonstrate that a memory is available in storage but not accessible for retrieval (Watkins, 1990). In contrast to memory as a thing, remembering is an embodied behavior that occurs, just like running is an embodied behavior that occurs. But we wouldn't say that running "goes somewhere" (e.g., into storage) when we stop running; instead it stops happening. "Reconstruct" is a lot closer, since it doesn't imply the existence of memory-entity storage in between occurrences of remembering. However, it's still a little awkward to talk that way, since we probably wouldn't say that we "reconstruct" running each time we start running again. Asking how the brain in some way causes the retrieval of memories involves a lot of metaphor (and sometimes even anthropomorphization of the brain as a causal agent) and therefore isn't really answerable in any kind of scientifically meaningful way [well, maybe if you're only interested in prediction... metaphors are useful for prediction, but not especially useful for influence]. You wouldn't say that the legs cause running (though they are part of what's going on), so why say that the brain causes remembering? However, you could say that he occurrence of embodied remembering behavior (i.e., as dependent upon the physical "braininess" of an integrated organism) is a function of current and historical context. Brains and legs don't exist in a vacuum; environmental contingencies cause behavior like remembering and running.
Paul,
"we wouldn't say that running "goes somewhere" (e.g., into storage) when we stop running;"
Thankyou for that analogy. It slows - if not stops in their tracks - what John Haugeland amusingly referred to as the 'sorry boxcars' trailing along behind the locomotive of Cartesian dualism. (Sorry for the contorted sentence structure).
"remembering is an embodied behavior"
Re-membering is putting the legs and arms back on :) As Kerstin Dautenhahn & Thomas Christaller proposed years ago, the computer storage metaphor for human memory is dubious because in human re-membering, the hard work is done on the 'output' end, not, as in computer storage,at the 'input' end. This paper may be of interest -
Remembering, Rehearsal and Empathy . Kerstin Dautenhahn & Thomas Christaller
In S. O'Nuillain, Paul McKevitt & E. MacAogain (eds.), Two Sciences of Mind. John Benjamins. 9--257 (1997)
"You wouldn't say that the legs cause running (though they are part of what's going on), so why say that the brain causes remembering?"
This perspective is so refreshing. It challenges the kind of cognitivist rhetoric which can lead you to assume that the 'body' exists as a plaything for the 'brain'. I cannot see how progress can be made in really understanding 'cognition' ( and by cognition I mean intelligent action in the world) until we abandon - or at least thoroughly examine - the structuring dualisms of mind/body and self/world. As I noted here earlier, axiomatic assumptions of this kind often impede science.
Simon Penny
Simon-
D'oh! That's right - you remind me that "recall" probably better captures the action of "calling out again." Thanks also for the ref.
John, Simon, Paul, …
I am grateful for this discussion on words and definitions, i.e. concepts, and susceptibilities. It helps me (hopefully) improving my vocabulary and maybe the further description of my hypothesis, referred above.
Memory “recall” is fine for me too. “Retrieve” used to be the word I thought to be the terminus technicus in neuroscientist’s world. But I will stay now with “reconstruction”. It describes best, what I want to say. It is the “conditions” that have to be reconstructed to remind us of what we learned and experienced and intend to do again. (And it is the word Dennis Gabor used.)
In my view, these conditions are strongly related to the endogenous waves and oscillations (rhythms) of the brain, which are strongly dependent on all biochemical brain states, which are strongly dependent on all neurotransmitters, modulators etc., which are strongly dependent on input wave and further more.
Ursula
Simon:
Should I be wary of all axiomatic ideas I might have in order to make progress in scientific matters?
Here are 3 axioms I genuinely believe to be true, and true for all:
...as has been the case through reading these last several posts. Thank you all for the multitude of thought-provoking insights you've so far exchanged here! It is an exhilerating feeling to have one's beliefs confirmed, is it not?
Indeed, one needs to understand both steps
a. How are physically stored (written, in computational terms)our memories in the brain?
b How are physically retrieved, extracted (read out, in computational terms) ?
Dorian:"a. How are physically stored (written, in computational terms) our memories in the brain?"
Memories are physically stored in two manners, 1. synaptic weights (percentage of ion channels in a synapse that respond to a particular signal) 2. Activation of protein genesis by activation of DNA to signal synaptogenesis. Note these are non-singular methods, and result in multiple storage locations responding to the same input.
Dorian:"b. How are physically retrieved, extracted (read out, in computational terms) ?"
Output comes in the form of release of neurotransmitters, and in some rare cases actual electric contact between cells. Note that because the output comes from a redundant input distributed across many cells, it is not a 1 to 1 mapping of input to output so it is not retrieved, but reconstituted or recalled.
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. Much of this is automatic analysis steps that bring out the meaning of the storage so that it can be dealt with.
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. There are it is estimated 33 networks in the brain that connect areas to other areas so that particular types of processing can be achieved.
Some of these networks define types of processing that are internal to the brain and therefore cannot be easily detected, but a small number of these networks such as the DMN , the DAN, the F-PN etc, have outputs that flow into other areas of the brain in such a way as to be detectable, and therefore functionally determinable. The Hubs where these networks come together are of interest in determining the use that the network has in the brain.
Of especial interest is the Central Networks that go down both sides of the Central fissure and seem to target modules in the cortex. It is thought that these have something to do with consciousness, and therefore represent a location that is important to retrieval.
a. Molecular structure is physically shaped inside neurons and synapses (e.g. protein folding) . In computational terms, fragments of memory are written inside neurons and synapses within molecular structure
b. These structures vibrate and generate a broad electromagnetic spectrum. In computational terms, meaningful fragments of information which are stored inside the structure are read out
During action potentials and synaptic activities (a) and (b) do simultaneously occur and meaningful information can be written and read out fast, a very different model of computation in the brain than the one presented in all textbooks (see neuroelectrodynamics)
Meaningful information in the brain is electrically (wirelessly) integrated and the presence of neurotransmitters, hormones... mediate such processes.The occurrence of neurofibrillary tangles and extracellular plaque, a systemic alteration of the life cycle of proteins within neurons and synapses leads to memory impairment.
Since similar fragments of meaningful information are distributed and stored within a large number of cells one can now understand such far more fluid involvement of hippocampus or neocortex
Ok, I'll take a stab at it.
The physical process involved in synaptic transmission for example, Is a complex one, that even I do not fully understand, but here goes.
When a pre-synaptic neuron fires, it secretes a chemical called a neuro-transmitter into the synaptic gap. This diffuses across the gap according to diffusion characteristics of the chemical. When it reaches a "Sensitive Patch" in the Post-synaptic neuron it triggers a chemical called a receptor, by changing the shape of the chemical as it docks with it. This is caused by bonds forming between the two chemicals which can be visualized using stereo-chemistry. The change in shape of the receptor, in turn triggers chemical changes within the cell because the receptor crosses the membrane of the cell. As it causes chemical changes by making it possible for chemicals to dock with the receptor on the inside of the cell, these chemicals trigger one of two different types of activity, either they trigger an attached ion channel, or they trigger the release of a secondary transmitter inside the cell, where it can diffuse through the cell causing changes in other chemical reactions within the cell.
Since some receptors allow the synapse to do both triggering an ion channel and releasing a secondary transmitter what happens next depends on which receptor is triggered. The ion channel selectively allows flow of ions either into or out of the cell, or may in complex ion channels allow the substitution of one ion for another allowing flow in both directions. Some secondary transmitters, work on the cytoplasm of the cell, and some operate on the DNA at the center of the cell causing it to trigger protein construction.
depending on which chemical changes are done by the secondary transmitter, different effects can be achieved. To know which effects you have to know the actual secondary transmitter. When both cytoplasmic chemical reactions and DNA are activated the results can be quite complex.
For instance in the case of LTP (Long Term Potentiation) repetative triggering of the receptor causes multiple chemical triggers to affect multiple DNA locations causing a basic change in the way that the receptor activates the cell. Depending on how fast these changes happen, you can get either LTP or LTD (Long Term Depression) out of the same receptor activations.
Ion channels can be as simple as small pores that allow ions to escape from the cellular cytoplasm, to more complex voltage gated ion channels that may respond to two or more receptors, and transfer ions depending on the state of the ion channel pore which can be blocked by the wrong ion being attracted to it. Voltage gates the ion channel by clearing the obstruction allowing the channel to open.
Ion channels can sometimes use ATP to pump ions against the charge gradient.
It is not a simple thing and there are hundreds of different types of ion channel/receptor combinations for a cell to choose between.
Is that the type of information you wanted?
OK, I have heard you spout this before, but we really don't know that that is the case.
We can follow the chemical reactions inside the cell, and see that some of them cause growth in the structure of the cell, but we can't prove that they cause storage of information in the structure of the cell, if only because we don't yet understand the limits of the processes triggered. What you are talking about is a theory of storage not a proven effect at all. I will accept that it MIGHT be true, because I can't prove that it isn't but I don't see the complex interface needed to store and retrieve structural information and release it back into the cell for activating the cell. How does your structural information get back out of the cell, and into the next cell? Until someone can prove how this works, my natural inclination is to say that it is a pipe dream.
The idea that the signal is electrical is interesting but again there is little proof while there is much more proof that the capacitance of the cell membrane acts as a filter against the transmission of signals wirelessly as you suggest. Even electrical signals that travel within the membrane are attenuated within 1/16 of an inch unless they are retransmitted. You are talking about much more subtle signals that aren't retransmitted by any mechanism except structural storage.
Graeme the biological story is correct "When a pre-synaptic neuron fires......" but it doesn't tell you what you need to know . Do you know how many neurons can be packed togheter within 1/16 of an inch?
The above explanation on page 6 is simple, anyone can understand the relationship between internal structure and generated electric field and well recorded rythms of the brain
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3636996/
Dorian without a support of a definition of "directability" not available in that publication, it is hard to judge the utility of the theory. It could quite easily mean that there are differences in the signals between different branches of the axion rather than that there are micro-signals in the Action Potential that are transferred wirelessly. In fact, I might suggest that within a cell, directability according to a micro-signal might work very well. The question which can't be answered directly by multiple depth implants, is, is the directability pre, or post synaptic. I would vote for pre-synaptic rather than post synaptic, especially since we don't completely understand the operation of the axion hillock, or how the signal changes depending on which branch of the axion responds to the signal.
First note that memories are not RETRIEVED. Rather, their neural representations are reactivated. Retrieval is a metaphor that best fits1950s computer models.
@ John S. Antrobus: let's not discuss about terminology. Memory retrieval is an expression, that everyone understands, but no one knows, how it's done.
I suppose that the different memory sytems have different neural substrates.
In this cause, terminology is important because it is diametrically opposed to the neural processes of memory . For example, the representations of the many features of a word, e.g. visual letter features, lexical word, various meanings of a word, are distributed with interacting/recurrent connections throughout most of the cerebral cortex. Each representation is a "memory." Some can be activated via bottom-up pathways, cross-modality pathways, others by both bottom-up and top (prefrontal) paths. The word "retrieval" just clouds the model building. Memory is a pretty vague term too in that, coined 3,000 years ago, it refers to the more public aspects of a activated represent - a fraction of the neural representations and processes by which it is produced.
You have a very good point there John. The word Memory is out of date, do I need to write a book and introduce a new term to describe the way that memory works, or are there others that are more academically inclined that can do that work better? I find it especially difficult to fit priming and delay memory into the mould of implicit memory.
You might like to look at O'Reilly's emergent neural network models http://grey.colorado.edu/emergent/index.php/Main_Page .There are many kind of priming - all work somewhat differently.
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