Explaining what déjà vu is and a very brief review over scientific findings and speculation concerning the déjà vu experience.

1. An Overview of Déjà Vu
Scientific findings and speculation concerning the déjà vu experience
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2. What am I going to talk about?
•A definition
•Facts
What is déjà
vu?
•Problems in finding the causes
•Some scientific explanations
•Brain parts involved in déjà vu
What causes
déjà vu?
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3. What is déjà vu?
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4. A definition
 Déjà vu is that feeling when you experience something familiar, but in fact it is novel.
 “We have all some experience of a feeling which comes over us occasionally, of what we
are saying or doing having been said or done before, in a remote time – of our having
been surrounded, dim ages ago, by the same faces, objects and circumstances – of our
knowing perfectly what will be said next, as if we suddenly remembered it” (Dickens 1849).
 Standard definition: Any subjectively inappropriate impression of familiarity of a present
experience with an undefined past.
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5. Facts
 Lifetime Incidence: Everybody experiences at least one déjà vu in his/her lifetime.
 Not Frequent: Healthy brains do not experience it very frequent.
 Decreases with Age: It starts from 8-9 and mostly happens when you are young.
 Education: Happens more to better educated people.
 Travel: There would be lots of new physical locations and logically, more chance of déjà vu.
 Fatigue: Déjà vu experiences are more likely when fatigued.
 Brain illness: Déjà vu can be associated with some brain illnesses.
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6. What causes déjà vu?
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7. Problems in finding the causes
We don’t know when déjà vu happens, it’s not frequent
Some methods are used for problematic brains, but …
Its results are not applicable to healthy brains
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8. Some scientific explanations
 There are lots of explanations, but none is certain.
 They fall into four categories:
1. Dual-processing explanations.
2. Neurological explanations.
3. Memory explanations.
4. Attentional explanations.
 We will have a quick brief over them.
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9. Some scientific explanations
Dual
Processing
Familiarity
and retrieval
Encoding and
retrieval
Perception
and memory
Dual
consciousness
Neurological
Seizure
Neural
transmission
delay
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Memory
Conflict in source
monitoring
processes
Duplication of
processing
Single-element
familiarity
Single-element
emotional
association
Gestalt familiarity
Attentional
Perceptual
fluency
Inattentional
blindness

10. Dual-Processing Explanations
This explanations assume that two cognitive processes
that normally operate in synchrony become
momentarily uncoordinated or out of phase.
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Novel experience
Perception
Memorizing
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1
Retrieve
Novel experience
Perception
Memorizing
1
2
Retrieve
Normal
Déjà vu
An example of dual-Processing explanations.
1 and 2 show precedence
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Neurological explanations
Suggest that déjà vu represents a brief dysfunction in
the nervous system involving either a small seizure or
alteration in the normal time course of neuronal
transmission.
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EEG results of a patient with TLE. Déjà vu is part
of the preseizure aura in some TLEs. A logical
extension is that déjà vu in nonepileptic individuals
results from a small temporal lobe seizure
TLE = Temporal Lobe Epilepsy
EEG = Electroencephalography

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Memory explanations
Memory interpretations assume that some aspect of
the present setting is objectively familiar but that the
source of familiarity has been forgotten.
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Attentional explanations
Attentional interpretations posit that an initial
perception under distraction is followed immediately
by a second perception under full attention.
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Distracted (Pay attention to the music)
Immediately after that - Paying attention to the scene

14. Brain parts involved in déjà vu
 According to scientific explanations, many parts of the brain can be involved in this
phenomenon.
 Temporal Lobe has been studied in many literature, since:
 Frequent déjà vu experience with longer duration is reported in patients with Temporal Lobe
Epilepsy (TLE).
 Hippocampus which plays important role in consolidating information and memorizing is in
Temporal lobe. Any malfunction of Hippocampus can have a role in experiencing déjà vu.
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15. Final words
 Although everybody experiences déjà vu during his/her life, still there’s no dominant
explanation for this phenomenon.
 Temporal lobe may be the part of the brain in which déjà vu can be triggered from.
 In Week 10, Module 1 to 3, Prof. Mason talks a little about attention in “Thalamic Attention”
lecture and she talks about Temporal lobe and Hippocampus in “The Story of H.M.” and
“Memory Formation Circuitry” lectures. Her notes about “implicit Perceptual Memory” in
“Memory Types” lecture somehow can be used in attentional interpretations of déjà vu.
They all helped me understand listed explanations about déjà vu.
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17. References
Mainly from:
 Brown, Alan S. "A review of the déjà vu experience." Psychological bulletin 129.3 (2003): 394.
Other resources:
 Warren-Gash, Charlotte, and Adam Zeman. "Deja vu." Practical Neurology 3.2 (2003): 106-109.
 Vlasov, P. N., A. V. Chervyakov, and V. V. Gnezditskii. "Déjà vu phenomenon-related EEG
pattern. Case report." Epilepsy & Behavior Case Reports 1 (2013): 136-141.
See also:
 https://www.youtube.com/watch?v=CSf8i8bHIns
 https://www.youtube.com/watch?v=foVMwJtlR5s
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