Deja vu comes from the French meaning previously seen. It is when you have a uncanny sensation that what you are currently experiencing is something which you have experienced in the past. Because you have no recollection of the past experience that the present one resembles, many people interpret it as a memory from a past life. There are several competing explanations of deja vu.
Information Processing Hypothesis
One explanation is that you have memory of a similar event. This is based on the hologram theory of memory. Although each level of the hologram has the entire memory as you go down to smaller pieces of the hologram, the picture gets blurrier. The brain mistakes the blurry picture of a past event for the present event, just as you might mistake what is going on in a blurry photo.
Global Matching Models of Memory
If the event is some what similar to several prior experiences the brain averages those experiences and the average is close enough to the event to trigger deja vu.
…imagine you are in an experiment in which you are shown pictures of various people in my family: my brothers…, my sisters…, my parents…, and so on. Now as you’re walking out of the experiment you happen to bump into me. You might have the experience of seeing me and thinking to yourself, “Hey, that guy looks familiar.” The reason for this is that although nobody in my family looks exactly like me (the poor devils) they all look somewhat like me and according to global matching models the similarity tends to summate.
The parahippocampal gyrus creates the feeling of familiarity. Josef Spatt has the hypothesis that deja vu occurs when you have no conscious memory of having been through the present event before, but the parahippocampal gyrus get triggered anyway.
Temporal Lobe Epilepsy
People who have temporal lobe epilepsy report having deja vu just before having a seizure. The seizure begins in the temporal lobe, which is important in creating and recalling memories. For this reason, some researchers think that for non-epileptics, deja vu is a small seizure in the temporal lobe.
This hypothesis is that deja vu occurs because the present event reminds you of a dream you had.
Short-term Memory Leak
This explanation is that the contents of the short-term memory leak into long-term memory making you feel like you have experienced the present event before.
©2016 Stephen L. Martin
Painting: Champs de Mars. La Tour rouge. by Robert Delaunay