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10 Cards in this Set

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Objective

List the functions of sleep.
During sleep, we rest our muscles, decrease metabolism, rebuild proteins in the brain, reorganize synapses, and strengthen memories. People who are deprived of sleep have trouble concentrating and become vulnerable to illness. Also, during sleep, a mammal’s body temperature decreases by 1 or 2 degrees Celsius, enough to save a significant amount of energy. Muscle activity decreases, saving still more energy. In fact, animals increase their sleep duration during food shortages, when energy conservation is especially important.
Objective

Discuss the specialization in the sleep pattern of dolphins and migratory birds.
See study guide.
Objective

Describe the effects of sleep deprivation.
• Dizziness, impaired concentration, irritability, hand tremors, and hallucinations
• Temporarily increase activity of the immune system
• Chronic deprivation can increase body temperature, metabolic rate, and appetite (body works harder)
It can compromise the immune system, decrease resistance to infection, and reduce brain activity.
Objective

Cite evidence that sleep enhances memory.
When people learn something and then get tested the next day, their performance is often better the second day than the first, but only if they get adequate sleep during the night. This implies that sleep enhances memory. Sleep also helps people reanalyze their memories. In several studies, researchers recorded brain activity as people learned a motor skill—similar to the skills you might learn in a video game—and then monitored brain activity during sleep. Later, they recorded brain activity while these people slept and found increased activity in the same areas that had been activated while these participants had been learning the skill. Furthermore, the amount of activity in those areas during sleep correlated highly with the improvement in skill seen the next day. These results suggest that sleep strengthens memories.
Objective

Describe the effect of REM sleep deprivation in humans.
Researchers observed the behavior of eight men who agreed to be deprived of REM sleep for 4-7 consecutive nights. During that period, they slept only in a laboratory. Whenever the EEG and eye movements indicated that someone was entering REM sleep, an experimenter promptly awakened him and kept him awake for several minutes. He could then return to sleep until he started REM sleep again. Over the course of the study, the experimenters found that they had to awaken the subjects more and more frequently, beginning with 12 times the first night and reaching 26 the final night. That is, people deprived of REM increased their attempts at REM sleep.
Objective

Discuss Maurice's theory about the role of REM sleep.
Maurice proposed that the primary role of REM is to shake the eyeballs back and forth enough to get sufficient oxygen to the corneas of the eyes. The corneas, unlike the rest of the body, ordinarily get much of their oxygen supply directly from the surrounding air, not from the blood. During sleep, because they are shielded from the air, they deteriorate slightly. They do get some oxygen from the fluid behind them, but when the eyes are motionless, that fluid becomes stagnant. Moving the eyes increases the oxygen supply to the corneas. According to this view, REM is a way of arousing a sleeper just enough to shake the eyes back and forth, and the other manifestations of REM—including dreams—are just by-products. However, many people take drugs that greatly restrict their REM sleep and they are not known to suffer damage to the cornea.
Objective

Explain the activation-synthesis hypothesis.
According to the activation-synthesis hypothesis, dreams begin with periodic bursts of spontaneous activity in the pons, which partly activate many but not all parts of the cortex. The cortex combines this haphazard input with whatever other activity was already occurring and does its best to synthesize a story that makes sense of all this information. Because activity is suppressed in the primary visual cortex (V1) and primary somatosensory cortex, normal sensory info cannot compete with the self-generated stimulation, and hallucinations result. The input from the pons usually activates the amygdala (portion of the temporal lobe essential for emotional processing), which explains why dreams have strong emotional content. Because much of the prefrontal cortex is inactive during PGO waves, memory is weak.
Objective

Explain why the activation-synthesis hypothesis is considered controversial.
One criticism of this theory concerns the role of the pons. Patients with damage to the pons continue to report dreams, even though they no longer show the eye movements and other typical features of REM. Therefore, some researchers argue that the pons cannot be essential for dreaming. The reply to this criticism is that none of those patients have very extensive damage to the pons.

Another criticism is that the theory’s predictions are vague. For example, if we dream we can’t move because our muscles are paralyzed during REM sleep, why don’t we always dream of being paralyzed?
activation-synthesis hypothesis
Dreams begin with periodic bursts of spontaneous activity in the pons—the PGO waves—which partly activate many but not all parts of the cortex. The cortex combines this haphazard input with whatever other activity was already occurring and does its best to synthesize a story that makes sense of all this information (see above for more information).
clinico-anatomical hypothesis
Theory derived from clinical studies of dreaming by patients with various kinds of brain damage. In several important regards, this theory resembles the activation-synthesis theory: in both theories, dreams begin with arousing stimuli that are generated within the brain, combined with recent memories and any info the brain is receiving from the senses (which are largely suppressed during sleep). The key difference is that the clinico-anatomical hypothesis puts less emphasis on the pons, PGO waves, or even REM sleep. It regards dreams as just thinking, except that the thinking takes place under unusual conditions (see above for more detailed information).