The temporal lobe containing the hippocampus formation is considered to be the part of the brain being essentiell for memory consolidation. However, things are more to be complicated...

definition of memory is still having no concensus among scientists. as i percieve memory is devided into two level: first engram that is represented in the brain due to some physical neuronal changes and the second the conscious awareness and behavioural expression.. i think that engrams are distributed all over the brain but the concentration may differ(more concentration may be in hippocampus area). as memory engram is concienved being a physical changes that may occur due to various reasons ie. pleasure activity may changes the brain reward circuit, motor activity will change cerebellum, reasonging and decision making medial frontal area. IF MEMORY IS LOCATED TO A PARTICULAR AREA, HOW THESE PHYSICAL CHANGES IN VARIOUS AREAS WILL GO AND RESTORED IN A PARTICULAR AREA ONLY?

Not if you think tht Karl Lashley, Alexander Luria, Kurt Goldstein and a host of others were correct

An engram or memory engram is an impression made physically/biochemechically in neural tissue of the brain by any mental stimulus, thereby explaining the persistence of memory

Simply, if you see what's going on with regard to aged people, loss of cortex neurons mainly and AD and SDAT, sure you will find the answer.

@donald stein sir, good researchers list for the distributed idea of memory

MIT is saying memory is stored in a specific brain cell, i accept but for ruling out the cells of the other brain areas they have to see other cells also, probably they concentrated on hippocapus cells. finding cells in that area does not prove that other areas are not involved

and second point: in a laboratory based controlled experiment, the rat/man does a very specific single simple task, but memory is not the memory of that experimental tasks only. there is possibility that the cells they found was specific to their experimental task, NOT IN GENERAL FOR MEMORY.

Wow, I did not expect so much response. Thank you for all your thoughts.

Alexey, if the brain would be only a hard drive which stores in units of 0 and 1, it probably would have already been rebuild by a computer.

In my opinion it is rather continously circulating information, so you are right that storage is probably not the right term. The thought about what kind of information is necessary to later retrieve it as meaningful is highly interesting, as the brain uses this high grade of abstraction. Draw two circles and link them with a rectangle over their midline and most of us would probably see a car or at least something which could move by rotation of the circles.

Alltogether, this may explain why sometimes for example an odor is perceived as something familiar, even if one was never exposed to this particular one.

This would support the theory quoted by Indrajeet of engrams influenced by experience and the actual conscious state.

By the way, I recently read somewhere (unfortunately can't remeber where) that the olfactory memory would be the most effective one, leading back to the question if such special kind of memory would also be located in the hippocampus.

P.S.: now I see, that I should have read the article posted by Alexey before formulating all my thoughts :-)

In response to the MIT article:

I ask myself, which other networks this specifically activated hippocampal neurons might have recruited that eventually led to the expression of fear (I would be surprised if the amygdala was not involved). Hard to say, if the memory of this former experience triggered by a light stimulus was only located in the hippocampus. Perhaps the hippocampus just builds some kind of central node where all the memories are connected with each other.

Hey Otago, I Postdoc'd there with Cliff Abraham, and used to hang out with Neil McNaughton's crew as well, both relating to the circuitry of learning and memory. Yes, learning and memory can be localized to individual circuits. However, there is overlap and redundancy. Primary of the structures studied is the Hippocampus, which is really part of a circuit or system, stretching back to the lateral entorhinal and perirhinal cortices, as well as stretching back to the medial entrhinal and parasubicular cortices. These cortices stretch back further, and so on. Hippocampus also has reciprocal connections with the amygdala, another structure involved with certain types of memory, the most popular of which is currently fear conditioning. hippocampus also connects to portions of the basal ganglia, specifically the striatum, which comprises the Caudate and pallidum are also inolved in another form of instrumental/motor/ or habit learning and memory. Hippocampus projects forward to multiple places of which the infralimbic cortex has received attention. monkey work has tradionally focused, in addition to the hippocapus, on the frontal cortex, specifically the dorsolateral frontal cortex. Work distinguising these systems from each other originated with lesion work. Can look up Mark Pacjard, James McGaugh, and Norm White, and Robert MacDonald for multiple memory system work. for the monkey work can look at Mishkin for hippocampus, and Elizabeth Murray as an entry into the prefrontal cortex literature. There is also the clinical work surrounding H.M., who had his hippocampus (and amygdala, surgically removed for epilepsy done by Brenda Milner, and later at MIT (closer to where he lived) by Suzanne Corkin. independent of the lesion literature there is a great deal of neurophyisology involving, individual neuronal activity during specific phases of various learning tasks, and within the hippocampal system itself the phenomenon of "Place cells" and in the last decade "Grid Cells". Then there is the a whole 'nother literature on inducing plastic changes in many of these systems, particularly LTP/LTD of which Cliff Abraham has worked upon most of his career down at Otago, and is respect4ed world over. Similarly Neil mcNaghton's work on a particular oscillation within the hippocampus (and the rest of the system) known as the rodent "theta" has also been implicated with place cells as a carrier wave, also potnetially being involved in learning.

To summarize there are multiple circuits and converging lines of evidence from human clinical, animal lesion work, pharmaceutical work and learning tasks, and electrophysiology that records, and induces different plasticity states.

Can check out all of this in an introductory format, fully illustrated and cross referenced on my old website Eric L. Hargreaves Page O' Neuroplasticity at:

http://www.pageoneuroplasticity.com

Good on yuh!

eric

PS: Although many circuits have been found to support plasticity phenomenon of LTP/LTD There has yet to be good evidence to show in vivo homosynaptic LTD in an awake animal. Read that last sentence carefully because its tricky. LTD in a slice is easy, some OK evdence in anesthetized animals for homosynaptic LTD in CA3/CA1, and plenty of heterosynaptic LTD in the PP/DG system, but only a single claim of homosynaptic LTD in CA3/CA1 in awake animals, that could not be replicated in Cliff'ss lab, when she came there to on her sabbatical in the mid90s (Flo Tiels, I think).Further, although LTP is easily found through the limbic system and parts of the caudate, and deep cerebellar nclei, and even transcallousally in the cortex... there are some very resistant structures to plasticity, such as the cerebellar cortex.

Only to add to Joachims link list:

http://newscenter.berkeley.edu/2011/09/22/brain-movies/

In my opinion it is pretty amazing that they are able to decode some of the information of the visual cortex in such a quality.

Hey Eric, I just arrived here in Dunedin for my postdoc but it is a very nice place to be.

Thank you for the link to your webpage.

It seems my idea of the hippocampus as a central coordinator is not completely wrong. You also make clear that a couple of regions are involved in the formation of several distinct forms of memory. Very interesting are your explanations to the phenomena of plasticity, especially the resistance of the cerebellar cortex. This is exactly what my question aimed at. Obviously, it is not such a widespread brain mechanism as I originally thought.

Dunedin was fun, used to live down on the beach in what was known as the castle. The only 3 story building along Esplanade. Tended to be filled with surfies in the summer, who would all then bug out in winter to queens town for skiing. I assume "The Cook" is still up and running (Captain Cook pub). Also hard to know if the cerebellum cortex is truly plasticity resistant, or if simply the right parameters have not been found. For example, what works best in the DG, ie the 400Hz 10pulse burst every minute for 20 bursts is not optimal at all for the CA3/CA1 circuit, and the theta burst protocol which was fairly effective and long lasting in the CA3/CA1 circuit did not last half as long as the 400Hz protocol in the DG. So many things to consider when inducing plasticity... Keep in touch as things progress. cheers

Yes Sir it is localized in particular parts of brain which is electrically maped out for clinicians. PCG,CLI

Thank you Dr christoph Lindemann wish you all the best in your research. pcg,CLI