New research on the potential benefits of sleep--including stronger memory and longer attention spans--were the focus of research presented by psychologists at the Western Psychological Association's 84th Annual Convention in Phoenix, April 22-25. The association's conference dedicated several sessions to discussing sleep, its effects on health and impact on social policy.
The conference featured leading experts in sleep research such as Cheryl Spinweber, PhD, of the Scripps Mercy Sleep Disorders Center, Richard Bootzin, PhD, of the University of Arizona, and Tracy Kuo, PhD, of the Stanford Sleep Disorders Clinic, who discussed a range of topics, including sleep's relationship to mood and Americans' pervasive sleep debt. James B. Maas, PhD, a professor and former chairman of the psychology department at Cornell University, headlined one session that discussed sleep's many benefits--such as improved health and memory.
"We have a crisis in America," said Maas, author of the best-selling book "Power Sleep" (Villard Books, 1998). "Most adults are moderately to severely sleep deprived, and it affects their productivity, their work and their relationships. If we treated machines like we treat the human body, we would be accused of reckless endangerment."
Maas stressed that good sleep isn't a luxury, but a necessity. "Your alertness, energy, performance, thinking, productivity, creativity, safety and health will be affected by how much you sleep," he said. "Good sleep is the best predictor of life span and quality of life."
Sleeping and learning
Besides boosting alertness, sleep--particularly rapid eye movement (REM) sleep--is a way for the brain to store new information into long-term memory, said Maas. The brain, he explained, accomplishes this through a phenomenon that researchers have only recently come to understand: sleep spindles.
Sleep spindles--one- to two-second bursts of brain waves that rapidly wax and wane at strong frequencies, so-called for the spike image they form on an EEG reading--occur during REM sleep. The REM phase usually takes place toward the end of the night, between the sixth and eighth hours of sleep, when people are most likely to dream. In fact, Maas said, the brain's neural patterns during REM sleep resemble those of its awakened state.
During REM sleep, the brain busily replenishes neurotransmitters that organize neural networks essential for remembering, learning, performance and problem solving, he explained. Conversely, he says depriving the brain of sleep "makes you clumsy, stupid and unhealthy."
For example, say you take golf lessons on a Wednesday to improve your swing before your next round on Saturday. After seeing progress, you sleep six hours each night for the rest of the week--about the median amount of sleep American adults get nightly.
However, "by the time the weekend comes around, you're worse off than if you had not taken the lesson at all," Maas said.
Why? During REM sleep, the brain transfers short-term memories in the motor cortex to the temporal lobe to become long-term memories, Maas said. Research suggests sleep spindles fire away as the temporal lobe makes sense of new information and stores it in long-term memory.
Yet sleeping fewer than six hours may block sleep spindles and stop new information from entering long-term memory, which helps acts such as a golf swing become automatic, Maas said.
While researchers have known of the spindles' existence for some time, only in recent years have they posited this theory, Maas said. For example, he noted that psychologists Matthew Wilson, PhD, of the Massachusetts Institute of Technology, and Alan Hobson, MD, of Harvard, have recently published breakthrough research on the subject by measuring the neural patterns of sleeping rats that had run a maze earlier that day. They found that the rats' brain patterns during sleep were nearly identical to the patterns they exhibited while running the maze. The patterns were so similar, in fact, that the researchers could tell what part of the maze the rat was dreaming about.
However, rats whose REM sleep was blocked did not navigate the maze as well during a second run as did rats with REM sleep. Some researchers contend that the results do not conclusively demonstrate that REM sleep is essential for short-term memory. Some studies find that antidepressant drugs that inhibit selective serotonin in the brain, which interferes with REM sleep, still do not disrupt learning and memory. But Maas said the research indicates that dreams are more than just abstract thoughts. Rather, they represent the brain's attempts to make sense of daily events, he explained.
"Practice during sleep is essential for later performance," Maas said. "If you want to improve your golf game, sleep longer."
Other research presented in Phoenix suggests that just as important as how long a person sleeps is how recuperative a person perceives their sleep as being.
Robert Hicks, PhD, professor emeritus at San Jose State University, said his research has found that some people say sleep completely rejuvenates them, while others feel they can't sleep enough--even though the two groups sleep the same amount. Hicks presented research he conducted using a self-report questionnaire that asks participants to rate whether they agree with statements such as "I feel I cannot think clearly," "I have trouble maintaining physical effort for long periods" and "I am less able to deal with emotional problems."
He found that participants scoring in the highest and lowest 20 percent slept nearly identical periods of time each night, but that 62 percent of low-fatigue people were satisfied with their sleep, while 68 percent of high-fatigue people were dissatisfied with it. And when he asked them how many additional hours of sleep they felt they needed each night to awake fully rested, the high-fatigue group reported that it needed about one and a half more hours, while the low-fatigue group reported needing only about an hour.
"They're sleeping almost the same, but they're perceiving the value of their sleep in a very different way," he said.
Why the difference? Hicks surveyed the two groups and found they varied in one unexpected area: The high-fatigue group reported suffering more frequently from post-traumatic nightmares and night terrors in which they relived awful, traumatic past experiences. These types of dreams are commonly associated with intense emotions even during sleep and can cause the dreamer to wake up frequently at night.
While Hicks continues to research this area to see if night terrors actually do contribute to the dreamers' perceptions that they did not sleep enough, he said that the effect of sleeping through emotionally intense night terrors might lead people to report that their sleep was not recuperative--even though they still slept the same amount as those who did not have traumatic nightmares.