Passage 2 Of all the components of a good night′ s sleep, dreams seem to be least within our control. Indreams, a window opens into a world where logic is suspended and dead people speak. A centuryago, Freud formulated his revolutionary theory that dreams were the disguised shadows of ourunconscious desires and fears; by the late 1970s, neurologists had switched to thinking of them asjust "mental noise"--the random byproducts of the neural-repair work that goes on during sleep. Now researchers suspect that dreams are part of the mind′ s emotional thermostat, regulating moodswhile the brain is"off-line." And one leading authority says that these intensely powerful mentalevents can be not only harnessed but actually brought under conscious control, to help us sleep andfeel better, "It′s your dream," says Rosalind Cartwright, chair of psychology at Chicago′s MedicalCenter. "If you don′t like it, change it." Evidence from brain imaging supports this view. The brain is as active during REM (rapid eyemovement) sleep--when most vivid dreams occur--as it is when fully awake, says Dr. EricNofzinger at the University of Pittsburgh. But not all parts of the brain are equally involved; thelimbic system (the "emotional brain") is especially active, while the prefrontal cortex (the center ofintellect and reasoning) is relatively quiet. "We wake up from dreams happy or depressed, and thosefeelings can stay with us all day." says Stanford sleep researcher Dr. William Dement. The link between dreams and emotions shows up among the patients in Cartwright′s clinic. Most people seem to have more bad dreams early in the night, progressing toward happier onesbefore awakening, suggesting that they are working through negative feelings generated during theday. Because our conscious mind is occupied with daily life we don′t always think about theemotional significance of the day′s events--until, it appears, we begin to dream. And this process need not be left to the unconscious. Cartwright believes one can exerciseconscious control over recurring bad dreams. As soon as you awaken, identify what is upsettingabout the dream. Visualize how you would like it to end instead; the next time it occurs, try to wakeup just enough to control its course. With much practice people can learn to, literally, do it in theirsleep. At the end of the day, there′ s probably little reason to pay attention to our dreams at all unlessthey keep us from sleeping or"we wake up in a panic," Cartwright says. Terrorism, economicuncertainties and general feelings of insecurity have increased people′s anxiety. Those sufferingfrom persistent nightmares should seek help from a therapist. For the rest of us, the brain has itsways of working through bad feelings. Sleep--or rather dream--on it and you′ll feel better in themorning. By referring to the limbic system, the author intends to show__________.
A.its function in our dreams B.the mechanism of REM sleep C.the relation of dreams to emotions D.its difference from the prefrontal cortex