湖南省汝城二中2014届高考英语一轮复习阅读训练 (24)_高考复习指南

湖南省汝城二中2014届高考英语一轮复习阅读训练 (24)

　　During the night, the deep sleepers were subjected to 14 different recorded sounds, like street traffic, toilets flushing, and an airplane flying overhead. Next door, the researchers monitored their sleep patterns and brain waves.

　　As expected, all of the participants slept relatively well, but there were differences in how they responded to the noisy interruptions. Some of the sleepers didn’t wake up even when a sound was blasted at 70 decibels（分贝）；others were awakened by sounds at 40 or 50 decibels.

　　The researchers discovered that the difference in a sleeper’s reaction to noise could be predicted by the level of brain activity called “sleep spindles（纺锤体）”. A sleep spindle is a burst of high-frequency brain activity coming from deep inside the brain during sleep. The source of the spindles is the thalamus（丘脑）, a part of the brain that sends sensory information to the rest of the cortex（皮层）.

　　Before the study, the Massachusetts researchers theorized that the spindles are the brain’s way of preventing sensory information from passing through the thalamus and waking the rest of the brain during sleep. They found that sleepers who experienced the most sleep spindles during the night were also the soundest sleepers and were least likely to be awakened by noise.

　　Scientists already know that most people become lighter sleepers with age, most likely because older people experience less “slow wave sleep”, which is the deepest stage of sleep. People also produce fewer sleep spindles as they age. But even when controlling for the stage of sleep a person was in, the number of sleep spindles still predicted their risk for awakening because of noise.