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Sticking point

点击量:   时间:2019-03-08 09:14:12

By Alison Motluk A STICKY switch in the brain may be at the root of manic-depression. Manic-depression is characterised by dramatic mood swings from euphoric highs to despair. No one knows what tips a patient from one extreme to the other. But now Jack Pettigrew and Steven Miller of the University of Queensland in Brisbane in Australia propose that the illness is the result of faulty switching between brain hemispheres. Many scientists believe that the dominant hemisphere of the brain, for unknown reasons, switches from one side to the other. Pettigrew and Miller point out that we preferentially take in information through one eye or the other, something they believe is one example of hemispheric switching. While investigating this, they tested whether manic-depressives differed from healthy people in how they did this. They asked 18 people suffering from manic-depression and 49 healthy people to look at a special screen. They placed an image of a horizontal grating pattern in front of one eye and a vertical grating in front of the other. Both images were visible at all times, but because of the preferential vision, only one or the other could be consciously viewed. Volunteers had to report when the image changed. Pettigrew and Miller found that healthy people flipped back and forth between images about every 1 or 2 seconds, but manic depressives took at least twice as long—and in some cases 10 times longer (Proceedings of the Royal Society B, vol 265, p 2141). “These people are stuck in one or the other hemisphere,” says Pettigrew,