Deja vu feeling all in the brain

Scientists in the United States say they have discovered a part of the brain responsible for the feeling of déjà vu.

Déjà vu, French for "already seen", is that uncanny feeling that one has witnessed or experienced a new situation previously; it is also called paramnesia.

Déjà vu is usually accompanied by a compelling sense of familiarity, and also a sense of "eeriness", "strangeness", or "weirdness" and the "previous" experience is usually attributed to a dream, although in some cases there is a firm sense that the experience "genuinely happened" in the past.

Déjà vu has often been described as "remembering the future" and is a very common phenomenon experienced by 70% or more of the population at least once.

It has been extremely difficult to create the déjà vu experience in laboratory settings, so few studies have been done on the phenomenon.

Scientists at the Massachusetts Institute of Technology in Cambridge, now say they have discovered the part of the brain that is responsible for déjà vu; they say neurons in the memory centre of the brain called the hippocampus make a mental map of new places and experiences, then store them away for later use.

They believe that déjà vu occurs when two events or places are very similar to each other, overlap and thus the feeling of déjà vu takes place.

Susumu Tonegawa, a professor of biology and neuroscience at the Institute says déjà vu occurs when this ability is challenged, and it is very important for an intelligent animal such as human beings so they are aware of what is going on around them and are then able to recall it later.

For their study, researchers used mice which have similar brain structures to humans.

Half the mice were genetically altered and were missing a gene in a specific part of the hippocampus, the others were healthy and they were trained to differentiate between different locations by giving them a tiny electric shock when they entered a particular spot.

When the mice were transferred from cage to cage they were given the shock in one specific cage; the healthy mice learned to realize which cage posed the dangerous shock, while the other mice were unable to do so.

Tonegawa says since they know the molecular and cellular pathway based on their results, there is a possibility to use those molecular targets to develop a drug to improve this connection.

The research is published in the journal Science.