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Origin of Deja Vu Pinpointed Dave Mosher The finding helps explain where déjà 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. “These animals normally have a distinct ability to distinguish between situations,” Tonegawa said, like humans. “But without the dentate gyrus they were very mixed up.” Déjà 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 déjà-vu-like confusion happens more often—and it also happens in people suffering from brain diseases like Alzheimer’s. “It’s not surprising,” he said, “when 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. “I 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. “But the rest of my brain knows better.”
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