Chapter 8.3: Why Sleep? Why REM? Why Dreams?

what happens to the body of an animal who hibernates?

-decrease their body temperature to only slightly above that of the environment (but not low enough for their blood to freeze) -heart rate drops to almost nothing -brain activity drops to almost nothing -neuron cell bodies shrink -dendrites lose almost a fourth of their branches, replacing them later when body temperature increases

activity is relatively high where in the brain during dreams?

-in the inferior (lower) part of the parietal cortex, an area important for visuospatial perception -also in the hypothalamus, amygdala, and other areas important for emotions and motivations

what happens to people who do not sleep enough?

-they react more severely than average to stressful events -may develop symptoms of mental illness or aggravate symptoms they already had -causes accidents in workers -causes poor performance in college students -body reacts as if it's ill

among adult humans, people who get how many hours of sleep a night have the highest percentage of REM sleep?

9 or more hours

define activation-synthesis hypothesis

a dream represents the brain's effort to make sense of sparse and distorted information

how much of their life does a person spend sleeping?

about 1/3 of their life

how much of their life does a person spend in REM sleep?

about 1/5 of their sleep, about 600 hours per year

define clinico anatomical hypothesis

an alternative view of dreams because it was derived from clinical studies of patients with various kinds of brain damage

why do you feel tired at the end of the day?

because inhibitory processes in your brain force you to become less aroused and less alert

what are some examples of species that get little to no sleep, but show no apparent harm to their health or alertness?

certain fish where there is no "day" or "night" because of constant water temperatures and brightness; dolphins and whales after giving birth, who stay awake 24/7 to watch after baby; birds decrease their need for sleep during migration

how do dreams begin according to the activation-synthesis hypothesis?

dreams begin with periodic bursts of spontaneous activity in the pons- the PGO waves- that activate some parts of the cortex but not others; 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 the information

what functions does sleep serve?

during sleep, we rest our muscles, decrease metabolism, perform cellular maintenance in neurons, reorganize synapses, and strengthen memories

what happens to hibernating animals every few days?

every few days they come out of hibernation for a few hours, raising their body temperature to about normal; they spend most of this time asleep

what does it mean when it's said that sleep shuts down activity at times of relative inefficiency?

for example, species with good vision are more effective during the day. since they cant be effective at night, sleep shuts them down because it is an inefficient time to work

in what way is REM especially important for memory storage?

for weakening the inappropriate connections

how does hibernation retard the aging process?

hamsters that spend longer times hibernating have proportionately longer life expectancies than other hamsters do

what did David Maurice (1998) suggest was the reason the eyeballs twitch during REM sleep?

he said that REM shakes the eyeballs back and forth enough to get sufficient oxygen to the corneas of the eye

species with the most hours of sleep also have the highest percentage of what?

highest percentage of REM sleep

what impairs does depriving people of sleep early in the night (mostly non-REM sleep) cause?

impairs verbal learning, such as memorizing a list of words, whereas depriving people of sleep during the second half of the night (more REM) impairs consolidation of learned motor skills

in what way does sleep help people reanalyze their memories?

in one study, people who had just practiced a complex task were more likely to perceive a hidden rule (an "aha" experience) after a period of sleep than after a similar period of wakefulness

what does the moving of the eyes in REM sleep do for the corneas?

it increases the oxygen supply to the corneas; REM is the way of arousing the sleeper just enough to shake the eyes back and forth

what memories does the hippocampus replay?

it replays recently learned patterns during quiet waking periods, not just during sleep

how exactly does sleep enhance memory?

patterns that occurred during sleep resembled those that occurred during learning, except that they were more rapid during sleep; the amount of hippocampal activity during sleep correlated highly with the subsequent improvement in performance; the brain replays its daily experiences during sleep

in what way is hibernation also a period of relative invulnerability to infection and trauma?

procedures that would ordinarily damage the brain, such as inserting a needle into it, produce little if any harm during hibernation

what do sensory stimuli do to dreams?

sensory stimuli, such as sounds in the room, occasionally get incorporated into a dream, although they usually do not.

how does sleep's contribution to memory relate to sleep spindles?

sleep spindles indicate an exchange of information between the thalamus and cerebral cortex; increase in number after new learning, and the number of sleep spindles correlates positively with improvements in certain types of memory

what does the clinico anatomical hypothesis emphasize?

that dreams begin with arousing stimuli that are generated within the brain combined with recent memories and any information the brain is receiving from the senses

the clinico anatomical hypothesis regards dreams as thinking that takes place under unusual conditions. what is one of those conditions?

that the brain is getting little information from the sense organs, and the primary visual and auditory areas of the cortex have lower than usual activity, so other brain areas are free to generate images without constraints or interference

how does spindle activity and IQ correlate?

the amount of spindle activity correlates more than 0.7 with nonverbal tests of IQ

what happens to a mammal's body during sleep?

the body temperature decreases by 1 degree Celsius or 2 degrees Celsius, enough to save a significant amount of energy; muscle activity decreases, saving more energy

why did David Maurice suggest that eye movement in REM sleep is due to the corneas needing sufficient oxygen?

the corneas, unlike the rest of the body, get oxygen directly from the surrounding air, but during sleep, when they are shielded from the air, they deteriorate slightly

why can't arousal lead to action in the clinico anatomical hypothesis?

the primary motor cortex is suppressed, as are the motor neurons of the spinal cord

what happens to the REM sleep of people who take antidepressants?

their REM sleep is severely decreased, but without incurring memory problems

what happens if people learn something and then go to sleep, even if it is just a nap?

their memory often becomes better than it was before the sleep

what happens to patients' dreams who have damage to the inferior (lower) part of the parietal cortex, an area important for visuospatial perception?

they have problems binding body sensations with vision, and report no dreams

what is the hypothesis of sleep's original function?

to save energy

true or false: bacteria have circadian rhythms of activity and inactivity

true

true or false: infants get more REM sleep and more total sleep than human adults do

true

true or false: the brain sometimes replays less common experiences more often than more common ones

true

the amount of NREM varies ________ among individuals and among species

varies less

what is the theory of why REM sleep happens toward the end of the night's sleep in regard to the fluid in the corneas?

when the eyes are motionless, the fluid behind the corneas that provides oxygen becomes stagnant; fluid is most stagnant by the end of a night's sleep, which is why it is suggested that REM sleep happens toward the end of the night

why do people have occasional dreams of falling or flying?

when you are asleep, you lie flat, unlike your position for the rest of the day... your brain in its partly aroused condition feels the vestibular sensation of your position and interprets it as flying or falling

in what way does sleep strengthen memories?

while you sleep, the less successful connections are weeded out, which weakens less appropriate synapses and emphasizes ones that were strengthened during wakefulness

an interpretation based on the activation-synthesis theory is that during REM sleep (which accompanies most dreams), what happens?

your motor cortex is inactive and your major postural muscles are virtually paralyzed; aka, when you are dreaming, you really cannot move, your feel your lack of movement, and thus, you dream of failing to move