Some people seem to be able to sleep through an earthquake while others wake up when someone treads on a squeaky floorboard. Researchers at Massachusetts General Hospital have been looking into this phenomenon and measuring people's brain waves to see if they hold the clue to it. When we are asleep sensory information passes through a part of the brain called the thalamus before passing on to the cortex which deals with thinking. Previous research has shown that brief rapid pulses of brain waves called spindles keep sensory information from passing through the thalamus and disturbing the cortex. In their study the researchers measured the brain waves of 12 people who spent three nights in the lab. The first night was quiet but on the next two nights the participants were exposed to increasing amounts of noise until their brain waves showed they were awake. The study found that those participants with the highest rates of spindle activity on the quiet night stayed asleep through higher levels of noise than the other participants.
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