Note
Studied by 7 peopleSleep and Waking Notes
Biorhythms
Seasonal migrations, mating seasons, and the human menstrual cycle are behaviors that occur at regular intervals due to internal biological clocks.
This chapter focuses on rhythms associated with sleep and waking.
Sleep and waking cycles follow circadian rhythms (daily rhythms).
The term circadian comes from Latin words for "about a day."
Ultradian rhythms: regular cycles of relative activation and quiet occur about every 90 to 120 minutes in a 24-hour day.
Internal biological clocks interact with zeitgebers (time givers) to maintain these rhythms.
Light is the most important zeitgeber for humans.
In the absence of natural light, human free-running circadian rhythms last approximately 24.2 to 24.9 hours.
Exposure to sunlight helps reset or entrain the internal biological clock to the 24-hour cycle.
Other zeitgebers include physical activity, feeding, body temperature, and sleep-related hormones.
When food is scarce, animals remain awake when food is available regardless of lighting conditions.
Ultradian Rhythms Characterize Wakefulness in Humans
Brain activity levels ebb and flow in 90 to 120 minute intervals during wakefulness, similar to REM cycles during sleep.
Chronotypes: individual sleep patterns resulting from different versions of internal clock genes.
Larks: People most alert and productive in the morning.
Night owls: People who have difficulty sleeping before midnight and waking up early.
Most people fall between these two extremes.
Having an owl chronotype is associated with a higher risk of death, likely due to conflicts with work schedules.
Connecting to Research: A Composite Scale of Morningness
Smith et al. (1989) developed a questionnaire to identify different chronotypes.
The Question: Can a questionnaire identify people with different chronotypes in a valid and reliable manner?
Methods: Administered three questionnaires to about 500 students, along with demographic questions, sleep complaints, and estimates of best sleep times and mental activity times.
Results: A composite scale was developed and validated with a new sample after analyzing the three previous scales.
Conclusions: The resulting scale appears to provide a good estimate of individual chronotypes.
A weakness is that it was developed using a college student sample, which isn't representative of the general public.
The scale has been used across many samples in over 1,200 studies with good results.
The Instrument:
Considering only your own “feeling best” rhythm, at what time would you get up if you were entirely free to plan your day?
5:00–6:30 a.m. (5)
6:30–7:45 a.m. (4)
7:45–9:45 a.m. (3)
9:45–11:00 a.m. (2)
11:00 a.m.–12:00 (noon) (1)
Considering only your “feeling best” rhythm, at what time would you go to bed if you were entirely free to plan your evening?
8:00–9:00 p.m. (5)
9:00–10:15 p.m. (4)
10:15 p.m.–12:30 a.m. (3)
12:30–1:45 a.m. (2)
1:45–3:00 a.m. (1)
Assuming normal circumstance, how easy do you find getting up in the morning? (Check one.)
Not at all easy (1)
Slightly easy (2)
Fairly easy (3)
Very easy (4)
How alert do you feel during the first half hour after having awakened in the morning? (Check one.)
Not at all alert (1)
Slightly alert (2)
Fairly alert (3)
Very alert (4)
During the first half hour after having awakened in the morning, how tired do you feel? (Check one.)
Very tired (1)
Fairly tired (2)
Fairly refreshed (3)
Very refreshed (4)
You have decided to engage in some physical exercise. A friend suggests that you do this 1 hour twice a week and the best time for him is 7:00–8:00 a.m. Bearing in mind nothing else but your own “feeling best” rhythm, how do you think you would perform?
Would be in good form (4)
Would be in reasonable form (3)
Would find it difficult (2)
Would find it very difficult (1)
At what time in the evening do you feel tired and, as a result, in need of sleep?
8:00–9:00 p.m. (5)
9:00–10:15 p.m. (4)
10:15 p.m.–12:30 a.m. (3)
12:30–1:45 a.m. (2)
1:45–3:00 a.m. (1)
You wish to be at your peak performance for a test that you know is going to be mentally exhausting and lasting for 2 hours. You are entirely free to plan your day, and considering only your own “feeling best” rhythm, which ONE of the four testing times would you choose?
8:00–10:00 a.m. (4)
11:00 a.m.–1:00 p.m. (3)
3:00–5:00 p.m. (2)
7:00–9:00 p.m. (1)
One hears about “morning” and “evening” types of people. Which ONE of these types do you consider yourself to be?
Definitely a morning type (4)
More a morning than an evening type (3)
More an evening than a morning type (2)
Definitely an evening type (1)
When would you prefer to rise (provided you have a full day’s work—8 hours) if you were totally free to arrange your time?
Before 6:30 a.m. (4)
6:30–7:30 a.m. (3)
7:30–8:30 a.m. (2)
8:30 a.m. or later (1)
If you always had to rise at 6:00 a.m., what do you think it would be like?
Very difficult and unpleasant (1)
Rather difficult and unpleasant (2)
A little unpleasant but no great problem (3)
Easy and not unpleasant (4)
How long a time does it usually take before you “recover your senses” in the morning after rising from a night’s sleep?
0–10 minutes (4)
11–20 minutes (3)
21–40 minutes (2)
More than 40 minutes (1)
Please indicate to what extent you are a morning or evening active individual.
Pronounced morning active (morning alert and evening tired) (4)
To some extent, morning active (3)
To some extent, evening active (2)
Pronounced evening active (morning tired and evening alert) (1)
If you scored 22 or less, you are an evening type, and if you scored 44 or more, you are a morning type. Scores of 23–43 are considered intermediate.
Nearly everyone acts like an owl during adolescence.
Teen sleep patterns might reflect a dramatic drop in melatonin at the onset of puberty.
Temporary owls will revert to their previous state after adolescence, possibly due to the maturation of the neural systems that regulate sleep.
A return to a previous sleep pattern in young adulthood might serve as a reliable indication that the brain is now fully mature
Shifting from a 7:15 a.m. start time to an 8:40 a.m. start time improved both attendance and student grades at Minnesota high schools
Other states, including California, have adopted later school start times for teens.
Shift Work, Jet Lag, and Daylight Saving Time
When employment demands conflict with workers’ chronotypes, it can result in poor health and greater danger to the public.
Shift maladaptation syndrome: Disturbed sleep and symptoms experienced by workers on the night shift (11:00 p.m. to 7:30 a.m.). *Circadian rhythm sleep–wake disorders—shift work type: Excessive sleepiness at work and impaired sleep at home for workers outside the normal day shift (8:00 a.m. to 6:00 p.m.).
Affects between 5 and 10 percent of night workers (16 to 20 percent of the total American workforce).
Middle-aged and older workers are at the greatest risk.
Shift workers obtain 1.5 fewer hours of total sleep than workers on other shifts, leading to health, personality, mood, and interpersonal problems.
Nurses on the night shift make 30 percent more errors than nurses working day shifts.
Accident rates are higher in the 3:00 p.m. to 11:30 p.m. shift and higher still during the 11:00 p.m. to 7:30 a.m. shift.
Larks appear to be more disrupted by shift work than owls.
Conflicts between internal clocks and external zeitgebers result in jet lag.
Fatigue, irritability, and sleepiness after crossing time zones.
North–south travel of equal distance does not produce the symptoms of jet lag.
Airline flight attendants who crossed time zones frequently had reduced reaction times and made more mistakes on memory tasks.
Insufficient recovery time exhibited evidence of temporal lobe atrophy.
Cognitive functioning and neurogenesis in the hippocampus were reduced, and depressive symptoms increased in a rodent model of chronic jet lag.
It is easier to adjust to a phase-delay (staying up and sleeping later) than to a phase-advance (setting the clock earlier).
Daylight saving time: Setting clocks forward 1 hour in spring (a phase advance) and back 1 hour in fall (a phase delay).
The fall shift produces relatively little disruption.
The spring shift produces symptoms similar to jet lag for a day or two.
Results in increases in a number of health conditions and in cardiovascular disease in particular.
The Body’s Internal Clocks Manage Circadian Rhythms
The body’s internal master clock is the suprachiasmatic nucleus (SCN) in the hypothalamus.
Located above the optic chiasm.
Input to the SCN comes from intrinsically photosensitive retinal ganglion cells (ipRGCs), which leave the optic nerve and project to the SCN, forming the retinohypothalamic pathway.
ipRGCs do not process information about visual images.
ipRGCs contain melanopsin, a photopigment.
The SCN is most active during the day, regardless of a species’ activity pattern (nocturnal, diurnal, cathemeral, or crepuscular).
SCN activity produces a response in the sympathetic nervous system, which communicates with the pineal gland.
As light decreases, SCN activity reduces, allowing the pineal gland to synthesize and release more melatonin, which modulates brainstem structures related to waking and sleep.
The SCN also manages other sleep-related changes, including body temperature, hormone secretion, urine production, and blood pressure changes.
The SCN is not dependent on input from other structures to maintain its rhythms. *Transplants of SCN tissue support its role as a master internal clock
A hamster with a transplanted SCN tissue will display the free-running cycle behavior from where the tissue came from
The SCN acts as a master clock that coordinates the activities of other internal, peripheral clocks that exist in most body cells.
Peripheral clocks in other tissues are much slower to respond to phase shifts than the SCN.
Increased light at dawn and decreased light at dusk change the firing patterns of the SCN, while light applied mid-day has little effect.
SCN astrocytes, unlike SCN neurons, are most active during the night.
Disabling these astrocytes lengthens circadian rhythms slightly, suggesting they finely tune the circadian activity of the SCN.
The Cellular Basis of Circadian Rhythms
The oscillation of protein production and degradation within a cell requires approximately 24 hours.
Research with fruit flies has identified genes and their protein products involved with cellular circadian rhythms, such as period and timeless.
During the night:
The period gene releases messenger RNA (mRNA) into the cytoplasm to produce PER protein.
PER binds with TIM protein (from the timeless gene).
PER/TIM complex reenters the nucleus and tells period to stop making more PER.
PER in the cytoplasm degrades during the day.
*lower levels of PER means less inhibition of period, so production gears up again, rising and then falling over a 24-hour cycle.
Neural activity reflects the oscillation of PER, providing a mechanism for communicating rhythms to other cells
Similar processes involving additional circadian genes and proteins occur in mice and other mammals, including humans.
Circadian genes in humans appear implicated in psychological disorders.
The Biochemistry of Circadian Rhythms
The SCN regulates the release of melatonin from the pineal gland into the cerebrospinal fluid of the third ventricle. *Lesions of the SCN abolish the circadian release of melatonin, demonstrating the dependence of the pineal gland on input from the SCN.
Melatonin levels are very low during the day, begin to rise before sleep, and usually peak at about 4:00 a.m.
Melatonin release is suppressed by light.
Melatonin supplements have been reported to improve cases of a number of sleep disorders.
Treatment with melatonin can be helpful in cases where visual impairments interfere with normal sleep patterns.
*Individuals with autism spectrum disorder have low levels of melatonin, and many appear to benefit from melatonin supplements to help regulate sleep patterns
*The existence of melatonin receptors in cells participating in the immune system has led to considerable research about the possibility of administering melatonin to improve immune function
*Because of its powerful antioxidant properties, melatonin supplementation has demonstrated potential for improving symptoms in a number of neurodegenerative disorders, such as Alzheimer disease
*Cortisol levels are normally high early in the morning and lower at night
*Higher levels of cortisol are associated with higher blood pressure, higher heart rate, and the mobilization of the body’s energy stores.
*In addition to normal daily fluctuations, cortisol is also released during times of stress
*As a result, stress-induced high cortisol levels during the night are correlated with poor sleep quality.
*Cortisol might also contribute to the detrimental effects of jet lag
*Flight crews who cross more than eight time zones have one third more cortisol in their saliva when compared with ground crews
*The stress of crossing time zones could stimulate cortisol release
Thinking Ethically: Artificial Lighting and Circadian Rhythms
*Discovery of inexpensive, artificial light sources has changed the light environment for many of the earth’s inhabitants.
*Less than 1 hour of exposure to artificial lighting, especially the new forms featuring short-wave or blue light (including fluorescent lights and phone and tablet screens), suppresses the release of melatonin
* Melatonin provides one of the key signals for the maintenance of circadian rhythms.
*Changes in melatonin release have been implicated in oxidative stress, decreased immune function, neurodegenerative diseases, and cancer in humans and animals.
*Blue-light reduction systems for portable electronic devices do improve sleepiness and saliva melatonin before bedtime, but overnight melatonin is not affected.
*High body mass index (BMI) and smoking are also linked to low melatonin levels, suggesting that maintaining a healthy weight and avoiding smoking could be helpful in offsetting some of the negative effects of artificial lighting.
*Most human growth hormone (GH) is released during the deep stages of sleep.
* In childhood, GH is primarily responsible for physical growth, but throughout life, it contributes to building muscle and bone mass and maintaining immune system function.
* The release of growth hormone peaks around the onset of puberty and begins to drop by age 21.
* Both growth hormone levels and the healing of injuries are reduced by sleep deprivation.
Neural Correlates of Waking and Sleep
Both waking and sleep are active processes choreographed by the brain.
Electroencephalogram (EEG) Recordings of Waking and Sleep
The EEG provides a general measure of overall brain activity.
Desynchronous brain activity arises from the relatively independent action of many neurons and is correlated with alertness.
Synchronous activity occurs when neurons are firing more in unison and characterizes deep stages of sleep.
The EEG During Waking
During waking, EEG recordings typically feature beta wave and alpha wave patterns of brain activity.
Beta activity: Highly desynchronized, rapid (14 to 30 cycles per second), irregular, low-amplitude waves.
Alpha waves: Slightly slower, larger, and more regular than beta waves, with a frequency of eight to 13 cycles per second.
Mu waves: Overlap in frequency with alpha waves (usually nine to 11 cycles per second) but are localized over the motor cortex.
*Gamma Band Activity: Waveforms >30 cycles per second. Prominent during processing of sensory input
Beta activity is prominent over the front of the brain and correlates with alert, active information processing.
Alpha activity is prominent over the back of the brain (visual cortex) and occurs when people are very relaxed.
Closing the eyes while awake will automatically result in the initiation of alpha activity.
*Mu waves are observed when a person is at rest but are suppressed by movement or the intention to move
*Theta activity characterizes lighter stages of sleep, although it begins to intrude into the waking EEGs of sleep-deprived individuals and may serve as a signal for a homeostatic need for sleep
The EEG During Sleep
*Sleep consists of alternating periods of rapid eye movement (REM) sleep and non-REM (NREM) sleep.
* NREM sleep is further divided into three stages.
*Sleep typically begins when a person enters stage 1 of NREM
*Alpha waves are gradually replaced with theta wave activity, and heart rate and muscle tension begin to decrease
*Muscle jerk, Myoclonia. It is often accompanied by a brief visual image. No harm is being done to the sleeper however
*After then stage 1 gives way to stage 2(comprising 50% of the nights sleep)
*Further reductions in heart rate and muscle tension
*The EEG begins to record sleep spindles, short bursts of 12 to 14 cycle-per-second waves lasting about half a second that are generated by interactions between the thalamus and the cortex.
*K-complexes also begin to appear in the stage 2 EEG recording. These waveforms are made up of single delta waves
*Occur spontaneously, they also occur in response to unexpected stimuli, such as loud noises
*Spindles and K-complexes are prominent in stage 2 but occur less frequently in stage 3.
*Might reflect the brain’s efforts to keep us asleep while continuing to monitor the external environment
*After about 15 minutes in stage 2, we enter stage 3 NREM sleep
*body temperature, breathing, blood pressure, and heart rate are at very low levels
*features delta wave activity, which is the largest, slowest (one to four cycles per second), most synchronized waveform of the sleeping state
*After approximately 90 minutes of NREM, a first period of REM sleep occurs
*Transition between stage 3 and REM involves stages 2 sleep
*The EEG demonstrates activity similar to waking beta activity accompanied by theta activity in the hippocampus
*The sympathetic nervous system becomes active. Rapid and irregular heart rate, blood pressure, and breathing
*At the same time, major postural muscles are completely inactive, effectively paralyzing the sleeper.
*REM has similar depravation effects to normal sleep looss
*Such as Irritability and difficulty concentration,
* Volunteers awakened each time they entered REM sleep and experienced REM rebound When allowed to sleep normally, they spent an unusually large amount of their sleep time in REM.
*The cycling between NREM and REM sleep in humans follows a characteristic pattern over 8 hours of sleep
*8The first 4 hours are characterized by longer periods of NREM and brief periods of REMStage 3 NREM is especially dominant in the first half of the sleep cycle.
Sleep Medicine
*Sleep evaluation used to mean that a person would need to sleep a minimum of one night at the center, but technology that is appropriate for home use is now available.
*To maintain quality of treatment, the American Academy of Sleep Medicine (AASM, 2022) coordinates its certification programs with the American Board of Internal Medicine and the American Board of Psychiatry and Neurology, reflecting the interdisciplinary nature of sleep.
Brain Networks Controlling Waking and Sleep
Networks Managing Waking
*Staying awake requires a complex network of structures in the brainstem and basal forebrain.
*A ventral pathway proceeds from the medulla to the posterior hypothalamus and on to the basal forebrain
*A dorsal pathway projects to the cholinergic mesopontine nuclei, located at the junction of the pons and midbrain. These neurons release acetylcholine
DMN and THOUGHT!
*The default mode network (DMN) consists of the medial prefrontal cortex, the medial parietal cortex, the lateral parietal cortex, and the lateral temporal cortex
*Activities associated with DMN include
*Mindwanding
*Retrieval of personally relevant memories
*Planning future events
*Areas that overlap for social behaviours
*thinking about other people’s beliefs, intentions, and motivations.
*combines external and internal factors to establish a context for understanding current situations (Yeshurun et al., 2021).
*For example, the DMN is active as we share or comprehend personal stories and experience fictional accounts.
*Earlier formulations viewed the DMN as restricted to managing spontaneous, intrinsic thought as opposed to external stimuli.
* earlier formulations viewed the DMN as restricted to managing spontaneous, intrinsic thought as opposed to external stimuli
*In healthy individuals, DMN connectivity predicts cognitive function.
*Adult > children 4.92 1.64 –1.64 –4.92 4.92 1.64 –1.64 –4.92 Adult > older adults p<0.001 p<0.001
NREM Sleep Networks
*Circuits involving the preoptic area (POA) of the hypothalamus manage homeostatic control of wakefulness or “sleep debt”
*POA are most active during NREM
*Electrical stimulation = immediate NREM
*Lesions = Insomnia
NREM AND DMN NETWORK!
*During NREM, frontal parts of the DMN decouple from the posterior parts, and the correlations between the activity in these two areas become nonsignificant
*Some of the same areas of the brain are active during both waking and REM sleep, such as the cholinergic mesopontine nuclei mentioned previously
*The muscular paralysis accompanying REM results from inhibitory messages traveling from the pontine reticular formation to the medulla and, from there, to the motor systems of the spinal cord
*twitching of fingers and toes occurs during both REM and NREM, but is more prominent during REM
*Each eye movement is accompanied by a waveform known as a PGO wave
*During REM sleep, many structures become as active or even more active than during waking
Biochemical Correlates of Waking and Sleep
*Acetylcholine (ACh) release by the pons and basal forebrain is associated with both waking and REM sleep. Cholinergic agonists, such as nicotine, produce an elevated level of mental alertness
*glutamate activity in the frontal lobes is high during both waking and REM sleep, and it is likely that glutamate promotes REM-on processes
*Some neurons in the thalamus and hypothalamus use histamine as their major neurochemical. These neurons project widely throughout the forebrain, and their activity is associated with alertness
*The activity of serotonin (from the raphe nuclei) and norepinephrine (from the locus coeruleus) is highest during waking, drops off during NREM sleep, and is very low during REM sleep
*Caffeine keeps us awake by blocking receptors for adenosine, an ATP byproduct that has an inhibitory effect on many brain systems When adenosine is inhibited, alertness is maintained
*For human beings, melatonin not only signals the onset of the dark cycle but also contributes to sleepiness
Why Do We Sleep?
*Adverse Effects of Sleep depravity
* traffic accidents, even when drivers are unaware of their sleepiness.
* contributed to the Three Mile Island nuclear meltdown in 1979, the Challenger space shuttle explosion in 1986
Changes in Sleep Over the Lifetime
*Newborn infants spend as much as 14 to 16 hours per day in sleep. About half of the newborn’s sleeping time is spent in REM sleep
*By the age of one year, the child’s sleep time has been reduced to 13 hours, which includes 1 to 2 hours of napping that will continue until about the age of three
*The amount of delta wave (stage 3 NREM) activity is highest between the ages of 3 and 6 years.
*Adults
*Time spent in stage 3 of NREM declines from 20 percent of the night in men under 25 years of age to less than 5 percent of the night for men over 35
*Around the age of 50, total sleep time begins to decrease by about 27 minutes per decade into a person’s eighties.
Sleep Keeps Us Safe
*Sleep prevents some animals from being active during parts of the day when they are the least safe from predation
*For example, the horse is a heavily preyed upon animal in the wild, and it generally sleeps out in the open. Consequently, wild horses sleep as little as 1 to 2 hours per day. Rabbits are also frequent prey, but because they have burrows in which to hide, they sleep much more than the horse.
Sleep Restores Our Bodies
*Sleep, particularly NREM, helps restore our bodies and conserve energy.
*Individuals who are deprived of NREM sleep will rebound or attempt to make up for this deprivation during their next opportunity to sleep.
*increased physical demands during the day correlate with a need for increased amounts of sleep the following night, reinforcing the role of NREM in the restoration of the body. Runners competing in ultramarathons add a surprisingly modest 20 to 30 minutes to their sleep the following night
*Human forebrain metabolic activity is greatly reduced during NREM sleep compared to waking
*In mice exposed to social stress, sleep had a restorative effect in reducing anxiety (Yu et al., 2022).
Memories Are Consolidated During Sleep
*The acquisition of new information and recall of stored information occur during waking, while consolidation occurs primarily during sleep
*The waking acquisition of new information produces unstable memories that are easily forgotten. Sleep offers an opportunity to consolidate memories without the distraction of massive amounts of new, incoming informationThe weak memories formed during the day can be strengthened, sorted, discarded, or embedded within existing memories.
*NREM sleep plays a key role in consolidation for those that do, such as your memories for the facts you’re reading in this chapter
REM FUNCTIONS IN THE BODY
*REM is associated with both the weakening and strengthening of synapses. It is possible that the familiarity or novelty of information determines whether the relevant synapses are strengthened or weakened
RECONSOLIDATING MEMORIES
*Memory becomes open for Modification
*The memory must undergo reconsolidation to become stable once more.
Sleep and Emotional Regulation
*Emotional events impact the next night’s sleep, and the quality of a night’s sleep impacts the emotions experienced the next day.
*Following sleep deprivation, people are more reactive to negative stimuli and under-responsive to positive stimuli.
*REM sleep might function to tone down or regulate the emotional associations of a memory
*One suggestion is that NREM plays a role in the extinction of fear
Why Do We Dream?
*Dreams are not synonymous with sleep stages. Brainstem lesions can abolish REM sleep, but the affected individuals still report dreams upon waking. Fore- brain lesions can abolish dreaming without reducing REM
*REM dreams are lengthy, complicated, vivid, and story-like, providing us with the sense of firsthand expe- rience with the events taking place. In contrast, NREM dreams are short episodes characterized by logical single images and a relative lack of emotion
*Common dreams content
*being chased, falling, flying, appearing naked, being unable to find a restroom, being frozen with fright, and taking exams for which one is unprepared
HYPOTHESES AND THEORIES
*The activation-synthesis theory of dreaming, arguing that the content of dreams reflects ongoing neural activity PGO waves
*evolutionary model, stipulating that animals evolved the ability to integrate sensory experience with stored memories during REM sleep rather than while awake, called evolutionary model of dreaming
*the threat simulation hypothesis, dreaming is viewed as a way to simulate escape from threat- ening situations
SLEEP TERRORS VS NIGHTMARES
NIGHTMARES
*REM Dream wuth disturbing events
*Nightmares are often mistaken for sleep terrors, but
Nightmares Content for Individuals without sight Content!
*being hit traffic
*Falling on the ground
*Being followed
*70% contain Negative emotional content!
###THREAT SIMULATION HYPOTHESIS
*Lucid dreaming associated
More activity in the **dorsolateral pre- frontal cortex **than is typically present in REM sleep
SLEEP TERRORS
NREM ,3 Hours prior!
Disoriented, Frigtened and Inconsolable
Mental imager is rare
There is usually no memory of the sleep terror the next