Deja vu and some specifics

Question

Deja vu is the feeling of having been where you are presently at some point in the past (usually pointed to dreams because you often cant remember dreams). What would you call that distant memory you cant remember having, in respect to the memory you are presently building? Is deja vu the bundle of 2 memories clashing or is it that distant memory you cant recall or is it that strange significant feeling youre having in the present and the distant memory is something else?

Answer 1

First according to Wikipedia definition of Deja vu:

It is an anomaly of memory whereby, despite the strong sense of recollection, the time, place, and practical context of the "previous" experience are uncertain or believed to be impossible. Two types of déjà vu are recognized: the pathological déjà vu usually associated with epilepsy or that which, when unusually prolonged or frequent, or associated with other symptoms such as hallucinations, may be an indicator of neurological or psychiatric illness,[10] and the non-pathological type characteristic of healthy people, about two-thirds of whom have had déjà vu experiences.[11][12][13][14][15] People who travel often or frequently watch films are more likely to experience déjà vu than others.[16] Furthermore, people also tend to experience déjà vu more in fragile conditions or under high pressure, and research shows that the experience of déjà vu also decreases with age.[17]

Thus I only restrict to talk about and try to explain the second type here since about 2/3 of non-pathological healthy people may have experienced Deja vu at some point in their life encountering. The same WP source further hinted a major possible candidate explanation for this strange yet common memory-related cognitive experience, and it kind of shows your disjunctive hunches to characterize Deja vu all seem on the right track!

Research has associated déjà vu experiences with good memory functions.[30] Recognition memory enables people to realize the event or activity that they are experiencing has happened before. When people experience déjà vu, they may have their recognition memory triggered by certain situations which they have never encountered.[16]... Two approaches are used by researchers to study feelings of previous experience, with the process of recollection and familiarity. Recollection-based recognition refers to an ostensible realization that the current situation has occurred before. Familiarity-based recognition refers to the feeling of familiarity with the current situation without being able to identify any specific memory or previous event that could be associated with the sensation.[34]

The "horse-race" model is a more recent view of dual process theories. This view suggests that the two processes of familiarity and recollection occur simultaneously, but that familiarity, being the faster process, completes the search before recollection.[4] This view holds true the idea that familiarity is an unconscious process whereas recollection is more conscious, thoughtful... At present, neuroscientific research has not provided a definitive answer to this controversy, although it heavily favors dual-process models.

Thus it's very important to view any declarative episodic memory recall in a Deja vu as most likely two processes instead of a single classic-conditioning like process. It's well-known from current episodic memory neuroscience knowledge that the recollection stage traces from any state of the sparse recurrent network within the hippocampus area like an attractor in dynamical system to eventually converge and thus accomplish a pattern completion to successfully recall a stored episode if any at all. On the other hand, as a type of priming and implicit memory the familiarity signaling process which is extremely evolutionarily important for us to quickly judge old and new experiences for making respective decision to survive, occurs in the temporal (perirhinal) cortex where more advanced and highly distributed and overlapped Hebbian like self-organizing learning is the norm which was further confirmed by Tanaka 2003 study referenced below.

The two modes may work in parallel, with a graded balance changing according to the behavioral context... Representation by multiple cells with overlapping selectivities can be more precise than a mere summation of representations by individual cells. A subtle change in a particular feature, which does not markedly change the activity of individual cells, can be coded by the differences in the activities of cells with overlapping and slightly different selectivities... Projection terminals from a single site of ventroanterior TE cover ∼50% of the perirhinal cortex. This divergence in projections may distribute the subtle differences over a larger area of the perirhinal cortex, so that objects recognized at individual levels can be distinctively associated with other kinds of information

Thus some sharpness produced by the single learning trial from the current experience enhancing existing synaptic plasticity distribution may act as a neural basis to treat this familiarity signal produced by the first and faster stage like a single graded value that continuously varies in intensity for different encounters and it may occasionally produce wrong value especially under high pressure dopamine related modulation effect, and later recall stage simply fails to retrieve such wrongly signaled episode even for a normal healthy person. Since these two stages are loosely independent without any pre-check mechanism, this could explain why most (two-thirds) healthy people are reported to encounter Deja vu when such occasional situation occurs.

Reference: Tanaka 2003, "Columns for Complex Visual Object Features in the Inferotemporal Cortex: Clustering of Cells with Similar but Slightly Different Stimulus Selectivities". Cerebral Cortex, Volume 13, Issue 1, January 2003, Pages 90–99,