Scientists from the University of Massachusetts - We found the area of the brain that is responsible for the formation of this mysterious feeling. Our experiments have shown that the main role is played by the neurons in the brain's memory center - the hippocampus. Specifically - it dentate gyrus, which allows you to quickly - almost instantly - to recognize subtle differences in a similar way.
Through the activities of this section a person realizes what impressions similar to those he had seen, and what is new in principle.
Hippocampus as it divides the human experience of the past and present. But when two impressions are very similar, in the hippocampus fails. Which leads to a deja vu.
This error occurred because of the similarity of situations. Man watching circumstances really have similarities with the past, confuses them - they are merged for him into one event.
That is the basis of the phenomenon lies just to the ability of the human brain associative thinking.
However, psycho-physiological cause of the phenomenon is still not clear: My only comment is that déjà vu is shown against the background of frequent fatigue and stress.