All of us have experienced being in a new place and feeling certain that we have been there before. This mysterious feeling is commonly known as déjà vu. Déjà vu is the dream like familiarity of something encountered for first time. It is more than just a sense that you have seen or done something before.
About 90% of people claim to have experienced déjà vu. Some people are convinced that déjà vu experiences are evidence of a past life. Others interpret it as prescience—the sudden ability to predict the future, at least for a few seconds.
The current theory says that déjà vu is caused by delays between the many parts of the brain involved in processing memories. For instance, an area called the hippocampus is important for storing long-term memories, and another part – the temporo-parietal junction – is important in recognizing something as familiar. Normally, these two systems work hand-in-hand but déjà vu may occur if there’s a temporary delay between them. This could lead to a false sense of familiarity being triggered without there being a true memory to base it on.
It’s caused by a chemical imbalance in the brain. When events are occurring in the present, our brain processes the activity in a part of the brain called the amygdala. Dejavu occurs when present events are processed in a part of the brain typically used to recall past memories. The parahippocampal cortex, which is very closely connected to the hippocampus. Because the event is processed in the parahippocampal cortex, it has a past ‘flavor’ associated with it.