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What causes deja vu?

One explanation for déjà vu is that there is a slight malfunctioning between the long and short-term memory circuits of the brain. Somehow, specific information shortcuts its way from short to long-term memory storage, bypassing the usual mechanisms used for storage transfer. The details concerning this shortcut are not yet well understood. When this new, recent piece of information is drawn upon, the person thinks that the piece is coming from long-term storage and so must have come from the distant past. A similar theory says that the error is in the timing of the perceptive and cognitive processes. Sensory information is rerouted on its way to memory storage and, so, is not immediately perceived. This short delay causes the sensation of experiencing and remembering something at the same time, a very unsettling feeling. One other explanation is that déjà vu is actually the process of remembering memory connections, of following the impulses and synapses. All of these neurobiologically based explanations for déjà vu seem plausible and intriguing and perhaps there is some overlap or combination that accounts for the different experiences we call déjà vu.

http://serendip.brynmawr.edu/exchange/node/1682

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