![]() ![]() What do EEG recordings tell us about sleep?ĭuring the fifth sleep stage, REM sleep, a stage of sleep characterized by rapid eye movements and a high level of brain activity, EEG patterns become hig h- frequency sawtooth waves, similar to beta waves, suggesting that the mind at this time is as active as it is during waking (see Figure 5.9). During waking, these changes involve alternation between hig h- frequency activity ( beta waves) during alertness and lowe r- frequency activity ( alpha waves) during relaxation. The EEG recordings revealed a regular pattern of changes in electrical activity in the brain accompanying the circadian cycle. But no one had been able to measure much of anything about sleep without waking up the sleeper and ruining it. Before this, many people had offered descriptions of their nighttime experiences, and researchers knew that there are deeper and lighter periods of sleep, as well as dream periods. In 1929 researchers made EEG (electroencephalograph) recordings of the human brain for the first time (Berger, 1929 see the Neuroscience & Behavior chapter). The sleep cycle is far more than a simple o n- off routine, however, as many bodily and psychological processes ebb and flow in this rhythm. 1- hour people living in a 2 4- hour world. This slight deviation from 24 hours is not easily explained (Lavie, 2001), but it seems to underlie the tendency many people have to want to stay up a little later each night and wake up a little later each day. Even people sequestered in underground buildings without clocks (“tim e- free environments”) who are allowed to sleep when they want tend to have a res t- activity cycle of about 25.1 hours (Aschoff, 1965). This circadian rhythm is a naturally occurring 2 4- hour cycle, from the Latin circa (about) and dies (day). The sequence of events that occurs during a night of sleep is part of one of the major rhythms of human life, the cycle of sleep and waking. And finally, the glimmerings of waking consciousness return again in a foggy and imprecise form as you enter postsleep consciousness (the hypnopompic state) and then awake, often with bad hair. More patches of unconsciousness may occur, with more dreams here and there. But then come dreams, whole vistas of a vivid and surrealistic consciousness you just don’t get during the day, a set of experiences that occur with the odd prerequisite that there is nothing “out there” you are actually experiencing. Time and experience stop, you are unconscious, and in fact there seems to be no “you” there to have experiences. Eventually, your presence of mind goes away entirely. On some rare nights you might experience a hypnic jerk, a sudden quiver or sensation of dropping, as though missing a step on a staircase. This presleep consciousness is called the hypnagogic state. ![]() As you begin to fall asleep, the busy, tas k- oriented thoughts of the waking mind are replaced by wandering thoughts and images and odd juxtapositions, some of them almost dreamlike. MOORE, ALBERT JOSEPH/BIRMINGHAM MUSEUMS AND ART GALLERY/THE BRIDGEMAN ART LIBRARYĬonsider a typical night. The world of sleep and dreams, the two topics in this section, provides two unique perspectives on consciousness: a view of the mind without consciousness and a view of consciousness in an altered state. Such altered states can be accompanied by changes in thinking, disturbances in the sense of time, feelings of the loss of control, changes in emotional expression, alterations in body image and sense of self, perceptual distortions, and changes in meaning or significance (Ludwig, 1966). Dream consciousness involves a transformation of experience that is so radical it is commonly considered an altered state of consciousness: a form of experience that departs significantly from the normal subjective experience of the world and the mind. But this is an oversimplification because the theater actually seems to reopen during the night for special shows of bizarre cult film s- in other words, dreams. Sleep can produce a state of unconsciousness in which the mind and brain apparently turn off the functions that create experience: The theater in your mind is closed. What’s it like to be asleep? Sometimes it’s like nothing at all. ![]() Why are dreams considered an altered state of consciousness? ![]()
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