You raised questions that I also always wondered about. I agree with the former comments in large parts. In my point of view questions like "where is the long-term memory" localized?" or "What is stored finally?" are arbitrary questions we ask, but which probably do not correlate well with what is happening in the brain over time. Imagine all the fascinating compensation mechanisms after large (cortical) brain damages. Imagine our ability for life-long learning and the reconsolidation of our knowledge. A good summary of how our long-term memory might change by any reactivation/remembering and incorporating new experiences in a "new" LTM (on synaptic and systems level) is given by Yadin Dudai (see here for free pdf: http://www.weizmann.ac.il/neurobiology/labs/dudai/uploads/files/Consolidation_Ann_Rev_2012_.pdf). I enjoyed the paper and I'm sure you will do so as well.

Neither LTM, nor knowledge is probably even close to be static. To find the ways the brain keep it dynamic is one big topic in the neurosciences.

Best,

-Max

RAM (random access memory) can be compared to a person's short-term memory and the hard disk to the long-term memory. The short-term memory focuses on work at hand, but can only keep so many facts in view at one time. If short-term memory fills up, your brain sometimes is able to refresh it from facts stored in long-term memory. A computer also works this way.The hard drive stores data on a magnetized surface that looks like a phonograph record.

Neuroscientists have classified the memory into two categories, long term and short term.

Working memory is where are the knowledge and the sensations or perceptions that are currently in use that are released or stored in long-term memory for later recall and use. It is therefore a portion of short-term memory, which deals with all the sensations that the body is exposed and seeks to organize them through the mnemic processes.

The long-term memory is that where effectively would be knowledge already cataloged and, remembering, charged of affective aspect, which makes them sui generis or rather, idiosyncratic. Tied specifically to the subject itself.

As far as I know, there is no specific locations for long-term memory. Once the information has been processed by the hippocampus, it travels through the brain to other regions, mainly cortical regions. Thus, if one has damages into the hippocampus he/she won't be able to store new information, but the one previously learned will remain intact (at least a big part of it). Regarding the last question, if you modify the information you stored, then you won't be able to recall it. You may make stuff up, so good memory is when you recall all the specific details. If you change the content, what are the differences between remembering and imagination? Memory is very complex to be separated into two categories. I never liked the term "short term memory", as I find it unuseful. There is an excellent paper by Cowan (2008) in which the distinctions between short-term and long-term memory are discussed. I'm sure you will enjoy it.

Best,

Javi

You raised questions that I also always wondered about. I agree with the former comments in large parts. In my point of view questions like "where is the long-term memory" localized?" or "What is stored finally?" are arbitrary questions we ask, but which probably do not correlate well with what is happening in the brain over time. Imagine all the fascinating compensation mechanisms after large (cortical) brain damages. Imagine our ability for life-long learning and the reconsolidation of our knowledge. A good summary of how our long-term memory might change by any reactivation/remembering and incorporating new experiences in a "new" LTM (on synaptic and systems level) is given by Yadin Dudai (see here for free pdf: http://www.weizmann.ac.il/neurobiology/labs/dudai/uploads/files/Consolidation_Ann_Rev_2012_.pdf). I enjoyed the paper and I'm sure you will do so as well.

Neither LTM, nor knowledge is probably even close to be static. To find the ways the brain keep it dynamic is one big topic in the neurosciences.

Best,

-Max

Respectfully, I would like to present a different approach. I do not believe memory is "stored" in one place per se. Brain is very dynamic, and I believe learning and memory relies on the fact that brain can alter its networks, and the quality of these networks constantly. Additionally, I think the use of LTM is not very good for categorizing the types of memories as far as the semantics. What do we mean by long-term? Is it a couple of hours or a month, or a few years? Different processes change with learning have different timelines. By drawing a line to separate LTM from STM in a continuous process may impair our understanding, or the way we design our experiments.

As Tumay said, memory relies on network plasticity, that is why it is so hard to define it. For me it is difficult to understand how the brain can "store" memories for a long time while renewing its network all the time ! There seems to be a complex equilibrium between plasticity and stability.

I think an interesting issue here is the use of the terms long-term and short-term memory. The operational definition of these terms varies from discipline to discipline. For example in cognitive psychology - where I believe these terms were coined - these terms refer to a computational model of memory processing. However, in my field, neurobiology of learning and memory, we generally define long-term memory as protein synthesis dependent and short-term memory as protein synthesis independent. So right off the bat, if one is discussing this topic the terms and constructs need to be clearly defined. If I am discussing long-term memory from the perspective of protein synthesis - which is required for long-term network plasticity changes - and another is imagining a hard drive analogue storage mechanism I think misunderstandings will result.

Therefore to your question about the location of LTM - you can see the issue. Where in the brain does protein dependent plasticity occur? All over the place! We know that there are certain structures which seem very important such as the hippocampus, amygdala, and cortex. However I don't think its correct to think of these locations as containing memories - rather they are locations of highly plastic networks. These networks contain multiple nodes - which might consist of a neuron or multiple neurons in another network altogether. These networks are representations and are also somehow maintained, even in the face of protein recycling and metabolic changes of the cells that they are consistent of.

The areas of the brain associated with these networks appear best suited to perform these tasks - just look at how well the hippocampus is set up for long-term potentiation. Interestingly though, we know that if we ablate the hippocampus, see Michael Fanselow - an organism can still make contextual memories (ie nominally hippocampus dependent)! It seems that rather than having brain structures which "store memories" the brain has default locations which are better at plasticity and have better connections to incoming signals from external stimuli.

@David Connor

Can we equate protein synthesis to information stored or knowledge stored?

No, protein synthesis is a fundamental cell function - one might say it is the cell's function, ie., DNA --> RNA --> protein. Anyway, we can have learning without new protein syntheses, the memory just doesn't last. We might call this short term memory. Basically, during learning there are changes in synaptic connections between neurons. These changes in synaptic connections require the neurons themselves to do things like shuttle in different receptors into the membrane, restructure the cytoskeleton, insert and remove ion channels, etc. This can all be done without protein synthesis from recycling proteins which have previously been translated. However, to stabilize these changes the cell needs to make new proteins - de novo synthesis.

I don't think any of these cellular changes can be equated to storage of information, however they appear to be necessary.

I would follow on Tumay's intriguing response by suggesting that the brain is just one part of a bigger, more distributed system. The brain need not "store" what the body's complex coordinations accomplish over very many time scales and over very many different parts of the body.

Here's an article that even suggests there might be representations stored "peripherally" through out the body in the case intermodal integration.

http://www.ncbi.nlm.nih.gov/pubmed/19000209

You might find Allan Baddeley's review of multistore models helpful.

Baddeley, A (2012) Working Memory: Theories, Models, and Controversies, Annual Review of Psychology, Vol. 63, pp. 1-29, 2012

This question highlights the limitations of the discourse we use to talk about mind, knowledge, thinking, memory and learning. We have to remember that this discourse is riddled with metaphor. Jean Lave (Cognition in Practice) refers to the traditional metaphor of the mind as a toolkit (where we “store” ideas, as if ideas were physical objects that we can manipulate and put away in a safe place, to be “retrieved” at a later time); Friere’s critique of education refers to the “banking” metaphor (where the learner’s mind is conceived as an empty piggy bank to be “filled” with bits of knowledge by the teacher); cognitive scientists employ the computer metaphor (where the human mind is viewed as an information processing system and thinking is a matter of computing); according to Roy Harris, communication is traditionally viewed as “telementation” (i.e. the “sending” and “receiving” of “messages”, a view which is based on the metaphor of the mind as a (fax) machine). Lakoff and Johnson (Philosophy of the Flesh”) provide the most thorough analysis of the various metaphors people use to talk about the mind; their point (and the point of Domenico’s question, I believe) is to highlight the fact that each of these metaphors embodies a set of underlying ontological assumptions, and to employ the metaphor is to grant tacit acceptance of those assumptions.

@Denise Morel.

Well said. I agree. And you deeply enlighten the point at issue.