psychology sleep SIS

sleep wake cycle

daily sleeping + waking periods create a variety of sleep patterns. sleep patterns are rhythms of sleep + waking so steady that they continue for many days

circadian rhythm

A 24-hour internal clock in our brain that regulates the cycles of alertness + sleepiness by responding to light changes in our env’t

explanation of circadian rhythm

• the central circadian clock in your brain, tells you when it is time for sleep

• it triggers pineal gland to release melatonin

• body’s internal clocks also in sync w/cues in the env’t

• light, darkness + other cues help determine when you feel awake or drowsy

adolescent circadian rhythm

biological + behavioural changes shift circadian rhythm which results in preference for later bed + wake up times

impacts of shift in circadian rhythm

• daytime sleepiness: early wake ups causes chronic sleep debt + tiredness

• mood + mental health: linked to stress, anxiety + depression

• academic performance: dec conc + mem due to lack of sleep

• physical health: impacts immunity, growth + overall wellbeing

key changes in circadian rhythm

• delayed release of melatonin: is released 1-2 hours later compared to adults, leading to later on set

• longer circadian period: sleep wake cycle lengthens beyond 24 hrs, making early sleep times harder

• inc sleep needs: require 8-10 hours but often do not get due to late sleep + early school starts

• inc evening alertness: feel more awake during evening due to delayed shift

2 process model of sleep regulation

• S represents build up + relief of sleep pressure

• sleep pressure accumulates while awake + dissipates while asleep

• process C represents circadian rhythm which promotes wakefulness + sleepiness

• sleep onset occurs when S is high + C is low, making both alignments crucial for feeling sleep at night + awake during day

build up of adenosine

• adenosine is the primary driver of sleep pressure

• our neurons burn ATP while we are awake. as ATP breaks down, adenosine levels in brain inc

• high adenosine inhibits wake promoting neurons, making us feel progressively sleepier

sleep deprivation

the condition of not getting sufficient sleep

light in the environment as a cause of sleep deprivation

• being exposed to bright lights at nighttime can dec the on set of melatonin production

• this can disrupt the sleep wake cycle

rapid eye movement

a type of sleep characterised by brain waves w/high frequency + low amplitude; the muscles in the body are in a state of paralysis + dreams may be experienced

non rapid eye movement

a type of sleep that is broken into 4 stages; where the sleeper falls deeper + deeper into sleep as the stages progress; characterised by relaxation of muscles, a slowing of physiological functioning + brainwaves that dec in freq + inc in amp

N1 sleep state

• transition from wakefulness; easily awakened

• alpha brain waves, low to med in amp, med to high in freq

• theta waves appear as stage progresses

N1 heart rate

• H.R slows

• breathing becomes irregular

N1 eye movement

• slow, rolling eye movement

N1 length + muscle tension

• 1 to 7 muns

• muscle tension dec; may have twitches

N2 sleep state

• true sleep on set; harder to wake but still can be by loud noise

• high prevalence of theta wave activity

N2 heart rate

continues to slow

N2 eye movement

no eye movement

N2 length + muscle tension

• 10 to 25 mins

• body temp drops

• relaxed muscles

N3 sleep state

• slow wave, very hard to wake

• if woken, will wake in confusion + may not remember the noise

• delta waves in high amp + low freq

• theta waves continue but delta appear

N3 heart rate

slowest + most regular

N3 eye movement

no eye movement

N3 length + muscle tension

• 20 to 40 mins

• very relaxed

• physical repair + growth

REM sleep state

• difficult to wake

• dreaming

• brain activity that appears like wakefulness

• no visual info is transmitted to the brain

REM heart rate

• beats fast

• breathing irregular + rapid

REM eye movement

rapid eye movements

REM length + muscle tension

• 10 to 60 mins

• muscles paralysed

sleep hygiene

healthy sleep habits or behaviours to optimise getting to sleep when desired + achieving the quantity + quality of sleep required for good mental health + wellbeing

limit screen time before bed to improve sleep hygiene

• avoid using 30 to 60 mins before bed

• blue light suppresses melatonin + engaging w/devices can mentally stimulate brain, making it harder to sleep

• research shows using bright screens for over an hour in evening delays melatonin release + inc alertness

keeps devices out the bedroom to improve sleep hygiene

• make room a screen free zone

• removing TV’s + pones from bedroom helps eliminate distractions + prevents sleep disruption from late night notis

• also trains brain to associate bed w/sleep

use night mode if you use screens to improve sleep hygiene

• turn on night mode or blue light filters if you must use devices

• these settings dec blue light emission + dim display, which can lessen melatonin suppression

• best practise is to unplug devices well before bed to allow mind to unwind

effect of restricting mobile phone use on sleep, arousal, mood + working memory

He et al, 2020

aim of he et al

to assess the effects of restricting mobile phone use before bedtime on sleep, pre-sleep, arousal, mood + working memory.

participants in he et al

38 university students with poor sleep quality + bedtime mobile phone use

• randomised to either an intervention group where they were instructed to avoid using phone 30 mins before bed or control group where they had no instructions

• 19 in each group

method to he et al

Thirty-eight participants were randomised to either an intervention group, where members were instructed to avoid using their mobile phone 30 minutes before bedtime, or a control group, where the participants were given no such instructions. Sleep habit, sleep quality, pre-sleep arousal + mood were measured using the sleep diary, the Pittsburgh sleep quality index, the Pre-sleep Arousal Scale + the Positive and Negative Affect Schedule respectively. Working memory was tested by using the 0-,1-,2-back task

findings of he et al

No significant diff between groups observed at baseline. these diffs observed

• Reduced sleep latency (~12 mins faster).

• Inc sleep duration (~18 mins longer)

• Improved overall sleep quality (better PSQI scores).

• dec cognitive + somatic pre-sleep arousal.

• Inc positive affect, dec negative affect.

• Improved working memory (accuracy and reaction times on 1- + 2-back tasks).

sleep latency

the time it takes to transition from wakefulness to sleep. Most healthy adults fall asleep within 10 to 20 minutes.  

contribution of he et al to psych

• Provides causal evidence linking bedtime phone use to poor sleep quality.

• Highlights pre-sleep arousal as a key mechanism.

• Offers practical behavioural strategies to improve mental health + cognitive performance.

• Supports research on sleep hygiene interventions.

limitations of he et al

• Small sample size (38 participants) limits generalizability.

• Relied on self-reported measures (e.g., PSQI, sleep diaries) instead of objective tools.

• Participants were motivated to red phone use (possible bias).

• Short-term (4 weeks); long-term effects unknown.

• Conducted on Chinese university students only

• Ethical issues minimal but close monitoring of phone use may raise privacy concerns