Origin of Deja Vu Pinpointed

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The brain cranks out memories near its center, in a looped wishbone of tissue called the hippocampus. But a new study suggests only a small chunk of it, called the dentate gyrus, is responsible for œepisodic memories”information that allows us to tell similar places and situations apart.

The finding helps explain where d©j vu originates in the brain, and why it happens more frequently with increasing age and with brain-disease patients, said MIT neuroscientist Susumu Tonegawa. The study is detailed today in the online version of the journal Science.

Like a computer logging its programs™ activities, the dentate gyrus notes a situation™s pattern”it™s visual, audio, smell, time and other cues for the body™s future reference. So what happens when its abilities are jammed?

When Tonegawa and his team bred mice without a fully-functional dentate gyrus, the rodents struggled to tell the difference between two similar but different situations.

œThese animals normally have a distinct ability to distinguish between situations, Tonegawa said, like humans. œBut without the dentate gyrus they were very mixed up.

D©j vu is a memory problem, Tonegawa explained, occurring when our brains struggle to tell the difference between two extremely similar situations. As people age, Tonegawa said d©j -vu-like confusion happens more often”and it also happens in people suffering from brain diseases like Alzheimer™s. œIt™s not surprising, he said, œwhen you consider the fact that there™s a loss of or damage to cells in the dentate gyrus.

As an aging neuroscientist, Tonegawa admitted it™s a typical phenomenon with him. œI do a lot of traveling so I show up in brand new airports, and my brain tells me it™s been here before, he said. œBut the rest of my brain knows better.

Source: http://news.yahoo.com/s/livescience/200 ... pinpointed