Sleep Flashcards
What are the differences between REM and NREM sleep?
REM sleep -> Rapid eye movements + brain is active
- Where most dreams happen
- Associated with Emergent Stage 1 EEG
NREM sleep -> Deeper sleep
- Initial stage 1, stage 2 + stage 3
- NREM 3 often referred to as slow-wave sleep (SWS)
What are the different sleep stages and the physiological characteristics unique to each stage?
REM sleep - Emergent stage 1 EEG
- High frequency/low voltage waves
- Loss of core-muscle tone
- Cerebral activity (e.g, O2 consumption, blood flow + neural firing) increases to waking levels
- Increase in variability in ANS activity (e.g. in pulse, blood pressure + respiration)
- Decrease in visual cortex, motor cortex + dorsolateral prefrontal cortex
NREM sleep - Initial stage 1, stage 2 + stage 3
- Deeper stages are characterised by lower frequency/higher voltage brain waves measured by EEG
Stage 2 NREM sleep
- appearance of k-complexes (sharp wave associated with inhibition of neuronal firing) and sleep spindles (rapid burst of higher frequency brain waves that last at least half a second)
How has research improved our understanding of dreaming?
- External stimuli can be incorporated into dreams
-> e.g. a study where ppts were lightly sprayed with later during REM sleep, many of them reported water-related content in their dreams - We dream in real time
-> when ppts are awakened during the onset of REM sleep, they are relatively accurate in reporting the duration of time they have been in REM sleep - Everyone dreams
- Sexual content is not necessarily associated with sexual arousal
-> Penile erections commonly assumed to be indicative of dreams with sexual content. However, erections are no more complete during dreams with frank sexual content than during those without it (Karacan et al, 1966). Even babies have REM-related penile erections - Sleepwalking has no particular association with REM sleep
What are the competing theories of sleep and what are the strengths and weaknesses of each theory?
Recuperation hypothesis:
-> Argues that sleep is important if not essential for physiological functioning
-> being awake disrupts homeostasis, sleep is required to restore it
- Restore energy levels
- Clear toxins
- Maintains homeostasis
- Consolidates memories
Adaptation hypothesis:
-> Suggests we do not need to sleep, but it is adaptive in relation to conservation of resources and less likely to lead to accident, predation, or injury
-> It suggests like sex, we are highly motivated to sleep, but we do not need it to stay healthy
- Association between vulnerability to predation and sleep duration
- Sleep is not a higher-order human function
- Analogous to hibernation
What are zeitgebers and what are the various types?
- Environmental cues (such as light-dark cycle) that control the timing of circadian rhythms
examples:
- Modified effects of food, social interaction, temperature and physical activity
- Jet lag and shift work -> subjects individuals to phase advance or phase delays - can cause fatigue
What are the effects on sleeping when there are no environmental cues?
- In absence of environmental cues, circadian cycle is maintained albeit on a slightly longer cycle
Free running rhythms -> circadian cycles in absence of environmental cues
Free running period -> average duration of this daily cycle - do not have to be learned
Individuals in lab environments experience internal desynchronisation -> when body temp cycle and free running periods decouple
What is the function of the SCN and how does it regulate circadian rhythms?
- Suprachiasmatic nuclei (SCN)
- Part of the hypothalamus
- Regulates our circadian rhythm
- Controls activity in other brain areas
- Is trained by optical detection of light dark cycles
What is the key research that isolated the SCN as a circadian clock and how did it affect the subjects?
Evidence for role of SCN by Richter (1967) -> found lesions in this area disrupted circadian cycles of eating, sleeping and activity in rats
- Does not change sleep duration
- When SCN was transplanted from fetal hamsters (mutant 20- hour cycle) to hamsters who had their 25-hour circadian cycles disrupted by SCN lesions, this restored their circadian cycle - to 20 hours
- When SCN was transplanted from normal hamsters, the 25-hour cycle was restored in the lesioned population
How does development affect circadian rhythm?
Adolescent sleep behaviour (social jet lag)
- Occurs across cultures
- Between species
- Result of increased sex hormones experienced during adolescence
- Predicts poorer grades and well-being in evening types (night owls)
- More likely to engage in impulsive risky behaviour
What is the role of melatonin in sleep?
- Secretion promotes sleep
- Regulated by SCN but released by pineal gland
- Exogenous administration (e.g. pills) may assist sleep
- Melatonin rhythm shifts according to environment
What areas of the brain are involved in sleep and what function do they carry out?
Hypothalamus
Anterior hypothalamus:
- Promotes sleep
Posterior hypothalamus:
- Promotes wakefulness
Baron Constantin von Economo -> casualties during WW1 who had trouble sleeping had anterior damage, while those who had problems with excessive sleep (struggling to wake up) had damage in posterior hypothalamus
Reticular formation (RF)
-> important for sleep
- Several areas of RF control different aspects of REM sleep
- Cardiorespiratory changes, muscle relaxation, rapid eye movements, twitches of extremities
What are the potential causes of insomnia and their associated symptoms?
Insomnia (lack of sleep)
Causes:
- Iatrogenic medication intolerance
-> caused by increased tolerance to medication
-> Sleeping pills may work in short-term but tolerance builds up and larger doses are required to maintain efficiency - can lead to addiction as reliant on medication
- Sleep apnea
-> Patient stops breathing which causes awakening
-> more common in males, the overweight and the elderly
Periodic limb movement disorder (PLMD)
-> Involuntary twitching during sleep of which they are unaware
-> In contrast Restless limb syndrome (RLS) sufferers are aware of uneasiness in their limbs
What are the potential causes of hypersomnia and their associated symptoms?
Hypersomnia (excessive daytime sleepiness)
Narcolepsy:
- Neurological condition that affects ability to regulate sleep-wake cycles
-> symptoms: severe daytime sleeping with repeated daytime napping
Cataplexy:
- Individuals lose muscle tone, can be mild + force the person to rest, or more severe causing a collapse
Hypnagogic hallucinations:
- Dreamlike experiences during wakefulness
Sleep paralysis:
- Inability to move when falling asleep or waking
REM disorders:
- When REM sleep occurs without core-muscle atonia - can cause patient to sleepwalk + act out their dreams
Why do alcohol and caffeine disrupt sleep and what neurochemical processes underpin these effects?
Coffee:
- Blocks adenosine receptors
-> adenosine is a chemical that reduces wakefulness and increases sleepiness
-> eventually (8hrs) caffeine is broken down + the accumulated adenosine flood the brain areas associated with sleep + wakefulness, causing caffeine crash and individual to feel sleepy
Alcohol:
- Sedative
- Promotes serotonin (affects our mood) and GABA (major inhibitory neurotransmitter in brain)
-> GABA tends to reduce activity of the signal-receiving neuron - slows brain down
-> many drugs that enhance GABA’s actions in the brain cause sedation and intoxication that resembles the effects of alcohol
- Disrupts REM sleep -> sedates individual + sends them to sleep, quality of sleep is poor
What are the overall physiological and psychological effects of sleep deprivation and the associated risks involved?
Characteristics of sleep deprivation:
- Increased sleepiness
- Physiological + behavioural disturbances
- Worsen with continued deprivation
- Sleep regained after end of deprivation
Psychological effects:
- Important consequences for health
- Negative self-reported mood
- Poor performance on attention tests
- Performance on complex tasks less consistent
Physiological effects:
- Reduced body temp
- Increased blood pressure
- Decreased immune function
- Hormonal fluctuations
Compare and contrast the differing effects of sleep deprivation on cognitive function and the reasons why they affect cognitive behaviour differently?
Tasks that depend on prefrontal cortex are more affected by sleep deprivation than tasks that involve logical deduction of critical thinking
-> people tend to perform better on tasks that are intrinsically interesting to them
Executive function:
- Prefrontal cortex dependent
- Decreased performance + increased stress on lateral thinking (e.g. brainstorming)
- Working memory (encoding and consolidation) affected
- Attention, performance and psychomotor speed reduced
Logical deduction + critical thinking:
- Less affected
- Due to increased challenge and engagement
How does sleep deprivation affect NREM and REM sleep?
REM deprivation:
- Increased initiation frequency
- REM rebound -> the more deprived of REM sleep an individual is, the more they tried to enter that phase the following night
NREM deprivation:
- Limits the amount of time spent in NREM sleep
- Feel tired + drained even if slept for long time
Contrast + evaluate the differing theories as to why we need REM sleep
- REM is important to replenish cognitive functioning
such as memory consolidation or emotion
-> evidence gathered from REM deprived studies where ppts did not suffer any emotional or cognitive issues argues against this - NREM sleep difficult to maintain - takes a lot of resources to keep us in deep sleep
-> more of an evolutionary adaptive hypothesis
-> need NREM sleep for physical functioning
-> we switch to REM sleep to give our body a rest and to recover
What are the reasons underpinning the differences between short and long sleepers?
There are no differences
-> you need as much sleep as you need
-> can depend on lots of factors: your own circadian rhythm, metabolism, physical fitness, genetics etc.
Describe the relationship between sleep deprivation and sleep efficiency and how it affects SWS
- Individuals who are sleep deprived tend to become more efficient sleepers
- When ppts are sleep deprived, SWS (NREM stage 3 - deep sleep) is regained over subsequent nights
- 6hr sleepers get the same SWS as 8hr sleepers
- Little SWS during morning napping
- Waking during SWS (deep sleep) affects next day sleepiness
Describe the method and results of Friedmann and Mullaney’s sleep reduction research and the implications for mood, health + performance
Method:
Within subjects - ppts were asked to reduce sleep
- 8 ppts
- Reduced sleep by 30 mins every two weeks to 6.5 hours
- Three weeks to 5 hours
- Four weeks thereafter until they did not want to reduce sleep further
Results:
- Two ppts stopped at 5.5 hours, 4 at 5 hours and 2 at 4.5 hours
- Found increased SWS (slow wave sleep, deep sleep)
- Found increased sleep efficiency - ppts slept better
- Found reduced time to fall asleep
- Found reduced number of nightly awakenings
No effects on mood, health + performance
What are the physiological and psychological effects of microsleeps/napping and why is this an effective method of sleep reduction?
Ellen - became the first person to circumnavigate the globe solo
- Slept for an average of 5.5 hours a day
- Achieved with naps with an average duration of 36 mins
- Ellen had 891 naps over 94-day voyage
Avoided sleep deprivation
-> no physiological or psychological disturbances
-> reason is because napping has higher than normal recuperative properties
Why is sleep an important determinant for long-term health when compared to exercise and diet?
Interrupted or poor quality sleep has important consequences for health
- Good sleep improves brain performance, mood and health
- Not getting good quality sleep raises risk of diseases and disorders e.g. diabetes,
List the strengths and weaknesses of cross sectional research such as Tamakoshi & Ohno (2004) and Nikbakhtian et al (2021)
and how it relates to the research on sleep deprivation
Strengths:
- Quick + cost effective
- Large sample sizes - increase generalisability
-> Tamakoshi & Ohno (2004) study, gathered data from over 100,000 people
- Can detect correlations between variables (sleep deprivation and health)
-> Nikbakhtian et al (2021) looked at how sleep deprivation affects decision making + cognition
Weaknesses:
- Correlational so can’t establish causality - longitudinal studies needed to confirm these findings
-> These studies don’t prove that reducing sleep causes you to live longer
-> But provide strong evidence that sleeping less than 8 hours is not the risk to life + health
- Other factors may influence results (e.g. diet, stress, exercise etc.)
-> hard to isolate effects of sleep deprivation
List the 5 dimensions of sleep health and the implications they have for health
Duration (how many hours of sleep you get)
- Associated with obesity
Continuity (how often you did/didn’t wake up - maintaining sleep)
Timing (what time you go to bed)
- Associated with accidents
Alertness (ability to maintain wakefulness during day)
Quality (‘good’ or ‘poor’ sleep)
- All associated with mortality + heart disease
- All but alertness associated with metabolic syndrome + diabetes
- Duration, continuity + quality associated with hypertension
- Continuity + alertness associated with depression
- Duration + Alertness associated with impaired neuro-performance
How can we improve our sleep routines and how are biological processes implicated in these processes?
- Stick to sleep schedule
- Exercise
- Avoid caffeine or nicotine -> coffee blocks adenosine receptors leading to increased wakefulness + decreased sleepiness
- Avoid alcohol -> disrupts REM sleep as it promotes serotonin + GABA
- Avoid large meals
- Avoid medication
- Don’t nap after 5pm
- Relax before bed
- Take a hot bath before bed
- Gadget-free room
- Get 30 mins sun exposure
- Don’t lie in bed awake
