Chapter 8 Notes
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Date Created: 04/19/16
Chapter 8 – Wakefulness and Sleep Human spends more time in sleep than in any other single activity Regardless of its purpose, sleep is an important behavior for psychologists to study, particularly in light of the millions of people whose lives are disrupted by their inability to sleep (insomnia) Endogenous circadian rhythm: the daily activities are controlled by a mechanism called a biological clock that is located in the hypothalamus SCN: suprachiasmatic nucleus receives axons of ganglion cells (W cells) from the retina It is the biological clock for daily activities: sleep and wakefulness Free running rhythm of 24 hours and 2 minutes: it needs to be reset by a mechanism called zeitgeber (time giver) For land animals, the zeitgeber is the sun light For aquatic animals, the zeitgeber is the tides Humans life in the cave for a long period of time will have a circadian rhythm of 25 hours People fly to a different time zone will suffer some physiological and psychological discomforts called jet lag Some statistics indicated that professional baseball teams had a better record on traveling to west than to east, because the human body has a circadian rhythm of 24 hours that it is easier to adjust to a long day than to a day shorter than 24 hours Melatonin is the hormone secreted by the pineal gland at dark, it can be used for jet lag, but it does not have a long term effect for sleep In addition to the endogenous circadian rhythm, some birds have the endogenous circannual rhythm The invention of the electroencephalography (EEG) made it possible to measure brain activity while people are sleeping EEG revealed that brain-wave patterns of sleeping people undergo changes during various periods of stages of the sleeping experience In addition to the EEG, electromyography (EMG) and electrooculography (EOG) are used to measure sleep stages Most of the time when we are awake, our brains show a rapid pattern known as beta waves (13-20 hz) that are low amplitude, desynchronized waves, i.e. neurons are active in a random fashion, producing fluctuations in voltage so out of phase that they tend to cancel one another out There is also wakeful period when brain waves slow down, producing a larger, slower, and more synchronized pattern, called alpha waves (9- 12 Hz) that are present when were are relaxed with both our bodies and mind at rest Meditation and yoga can produce alpha waves Slow-wave sleep (SWS) is interchangeable with S-sleep, non-REM sleep, and N-REM sleep The onset of sleep is accompanied by a further slowing of the brain wave pattern, as well as a more rhythmic and uniform fluctuation i.e. the neurons begin to work in phase This new pattern, in which the brain waves become much larger and much slower, slows from 9 to 12 Hz to 1 to 3 Hz (delta waves) as the person falls into deep sleep This process does not occur abruptly, it is a gradual process Stage 1: Starts to see some delta waves and a person is in a light sleep state Stage 2: More delta waves are present, occasional bursts of 12 to 14 Hz waves, known as sleep spindles, and K complex can present when some stimulation occurs to a person Stage 3: A lot of delta waves (slow waves) present and a person is in a deep sleep state Stage 4: Full with delta waves and a person is in a deeper sleep state, it is very hard to be awaken by outside stimuli The transition from the beginning of sleep (stage 1) to deep sleep (stage 4) spans roughly 45 minutes After reaching deep sleep, the brain-wave pattern reverses, gradually moving from stage 4 to stage 1 over a similar time span The so called sleep cycle is 90 minutes Approximately 80% of the normal sleeping period is spent in S sleep, the remaining 20% of the time is spent in a state called rapid eye movement (REM) sleep or paradoxical sleep in animals Approximately 90 minutes after a person first went to sleep, you would notice a dramatic change in the brain wave pattern Suddenly, the pattern would become far more rapid, with a less amplitude (similar to the beta wave) and it is called the REM sleep REM sleep is also called D sleep (D stands for desynchronize of the waves), desynchronized sleep, active sleep, or paradoxical sleep in animals that doesn’t have rapid eyes movement during that period of sleep For most of people, REM sleep continues for about 10 minutes, then the slow wave cycle resumes Less than an hour later, the REM sleep pattern returns, lasting slightly longer than the first time As the night progresses, the periods of slow wave sleep gradually diminish Stage 4 and eventually stage 3 drop out – and the periods of REM sleep gradually increase Dreaming occurs primarily during REM sleep, in studies conducted by Nathaniel Kleitman and William Dement, most people awakened during REM sleep reported that they had been dreaming Some dreaming occurs during S sleep too, albeit to a much lesser extent than during REM sleep During REM sleep, EOG records the movement of the eyeballs and EMG indicates the relaxation of muscle tension that may protect dreamers from physically acting out of their dreams During S sleep, heart rate and respiration tend to be much more regular than during REM sleep The more emotional the dreams, the more intense the automatic signs Changes in sex organs also occur, penile reaction in males and increased vaginal blood flow in females appear more frequently during REM sleep than during S sleep, though neither seems to be correlated with erotic dreams Humans and most animals appear to have built-in biological clocks that control sleeping and waking patterns on a remarkably rhythmic cycle (25 hour circadian rhythm) If a person is deprived of REM sleep for a couple of nights, a phenomenon of REM rebound will occur During the first recovery night, the person will fall in REM sleep quickly and spend 60% of the sleep time in REM The effect will spread to the second recovery night in which more than 20% (normal REM) of the sleep time is REM sleep This indicates that the REM sleep is biologically important to humans, you lose it and you will make it up in the next two days, infants spend much more of their sleep hours in REM sleep than adults do (20%) as much as 50% of the time In 1935 Fredric Bremer surgically interrupted sensory input to the brain of a cat and observed to the resulting EEG recorded from the cortex during sleeping and waking hours Firstly, he made a cut between the base of the brainstem and the spinal cord and thus eliminated all sensory input from below the neck Results: EEG activity still revealed normal sleep-wake pattern Secondly, he attempted to eliminate input from the cranial nerves as well as from below the neck He made a cut between the upper part of the brainstem at the midbrain level and the rest of the brain, thus eliminating all sensory input to the cortex except that from the optic and olfactory nerves, both of which enter the brain above the midbrain cut Results: abolish waking activity, causes the cat to enter a comatose state The data were interpreted as indicating that the signal for the sleep- wake cycle depends on neural input from the sensory system But there is a possibility that detaching the brainstem from the upper part of the brain producing sleep for reasons other than the reduction of sensory input It is possible that the brainstem does something to the cortex to maintain wakefulness These doubts have been confirmed by experiments indicating that it is not the sensory input passing through the brainstem that plays a vital role in maintaining wakefulness, but other connections between the brainstem and cortex Donald Lindsley and his colleagues have confirmed that the brainstem, per se, is the critical factor in control of wakefulness Taking great care to leave the sensory pathways to the cortex intact, they lesioned the midbrain reticular formation in the brainstem, and this lesion abolished wakefulness; the animals went into permanent coma It appears that Lindsley’s procedure damaged a center for waking Other scientists reported that electrical stimulation delivered to the midbrain reticular formation was sufficient to wake a sleeping cat; whereas the same stimulation applied to other areas had no such arousing effect It appears that wakefulness is controlled by the midbrain reticular formation and its circuits to the upper parts of the …? Cats are used to study the neural control of the paradoxical sleep and S sleep because cat’s EEG show both types of sleep patterns Cats also show a unique spiking pattern during paradoxical sleep in 3 areas: the pons, the lateral geniculate nucleus, and the occipital cortex This pattern is called PGO spikes According to Jouvet, paradoxical sleep is controlled by the locus coreuleus (blue space), an area in the pons in connection with the neurotransmitter norepinephrine Lesions in this area abolish paradoxical sleep, as do injections of drugs that block norepinephrine The locus coeruleus controls cortical activity (via the giantocellular tract) and motor inhibition (via descending connections to the spinal cord) by releasing norepinephrine S Sleep is controlled by the anterior nucleus of the raphe (seam; stitching in Greek) system located in the pons Lesions in this area abolish S sleep but not paradoxical sleep The anterior nucleus of raphe is connected to the locus coeruleus, and according to the active theory, when the anterior nucleus of the raphe is active it produced S sleep By inhibiting activity in the locus coeruleus The anterior nucleus of the raphe contains a large amount of serotonin which controls S sleep Blocking of serotonin produces insomnia When the anterior nucleus of the raphe is active, a high level of serotonin inhibits the locus coeruleus and the results is S sleep When the anterior nucleus of raphe becomes inactive, serotonin levels are low, the inhibitory effect on the locus coeruleus is removed, and the result is paradoxical sleep The two principal sleep disorders are insomnia and narcolepsy Approximately 2/10 persons suffer from insomnia at some time in their lives Insomnia takes more than one form: onset, maintenance, termination Some insomniacs fall asleep easily enough but dram that they are awake They felt as groggy once they awaken as if they had in fact spent a sleepless night Some insomniacs suffer from a problem known as sleep apnea These people suddenly stop breathing shortly after they fall asleep and then are forced to gasp for air Most attacks are mild and the person usually does not wake up Two factors are related to sleep apnea 1. The respiration centers in the brains of some insomnicas who suffer from sleep apnea are apparently unable to monitor and respond to the change in the level of oxygen in the blood that occur during sleep 2. Other insomniacs are unable to breathe because their air passage is obstructed by the over-relaxation of muscles in the throat that occurs shortly after they fall asleep A surgical procedure, known as a tracheotomy (putting a permanent hole in the trachea so that air to the lungs is not blocked during sleep) has proven effective Some cases of SIDS (sudden infant’s death syndrome) may be related to the sleep apnea Perhaps as many as 3/1000 suffer from narcolepsy Suddenly, in the midst of such routine activities as having a meal, driving a car, or standing in front of a group of people talking A narcoleptic will be seized by an overwhelming need to sleep and will remain asleep for anywhere from 5 minutes to half an hour Apart from these sudden attacks or sleep, narcoleptics are also subject to brief episode of muscle weakness or paralysis that are usually elicited by a strong emotional experience, the person will often simply crumble to the group These attacks, known as cataplexy, are not accompanied by sleep Occasionally, narcoleptics experience unusually vivid dreams at the onset of sleep known as hypnagogic hallucinations There are drugs available that can reduce the number and the severity of the attacks Narcoleptics are also being trained by a technique known as biofeedback to recognize the very subtle but specific sensation that nearly always precedes an attack In this way, at least, they can remove themselves from a potentially dangerous situation (pull over to the side of the road if they are driving) before the attack strikes
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