The Nature of Sleep

Links to the Specification Develop a critical understanding of the nature of sleep – what happens during sleep and its possible function.

Past Exam Questions Outline the nature of sleep (8 marks)

Organisation By the end of this topic you should be able to: Describe the stages of sleep and the distinction between different types of sleep. Describe the different stages of sleep and comment on research that has explored each stage. By the end of this topic you should be able to: Describe the stages of sleep and the distinction between different types of sleep. Describe the different stages of sleep and comment on research that has explored each stage.

Independent Work/Reaching the A* Grade Complete all lecture notes and hand outs to a high standard. Complete ‘cut and stick’ activity on stages of sleep. Complete A4 sleep stages grid. Complete core reading – Dement and Kleitman (all students) Complete extension reading – Dement and Kleitman journal article (A*/A) Complete summary questions. Complete self-assessment marking activity (8 markers) Complete gap fill quiz. Complete all lecture notes and hand outs to a high standard. Complete ‘cut and stick’ activity on stages of sleep. Complete A4 sleep stages grid. Complete core reading – Dement and Kleitman (all students) Complete extension reading – Dement and Kleitman journal article (A*/A) Complete summary questions. Complete self-assessment marking activity (8 markers) Complete gap fill quiz.

Key Terms ElectroencephalographySlow Wave SleepAlpha Waves Rapid Eye MovementSleep SpindlesDelta Waves DesynchronisationTheta WavesBrain Waves Visual ImageryThalamusCortex Paradoxical SleepFrequencyMetabolic Rate

Siamese Twins – Do they have the same sleep patterns? 1970s Lenard and Schulte studied the sleep patters of a pair of German Siamese twins co- joined at the head. They had extensive connections between their blood supplies but separate EEG recordings. They had different sleep/wake cycles. Sadly they died aged 21 during surgery. 1970s Lenard and Schulte studied the sleep patters of a pair of German Siamese twins co- joined at the head. They had extensive connections between their blood supplies but separate EEG recordings. They had different sleep/wake cycles. Sadly they died aged 21 during surgery.

Stages of Sleep

Wakefulness and sleep = circadian rhythm But within sleep portion = ultradian rhythm 5 stages of sleep 1 st four stages = NREM sleep 5 th stage = REM sleep One sleep cycle goes through all five stages and lasts 90 mins. Most people have 5 cycles of sleep per night. Wakefulness and sleep = circadian rhythm But within sleep portion = ultradian rhythm 5 stages of sleep 1 st four stages = NREM sleep 5 th stage = REM sleep One sleep cycle goes through all five stages and lasts 90 mins. Most people have 5 cycles of sleep per night.

How do we measure activity during sleep?

Electroencephalographs (EEGs) Measure electrical activity or brain waves Electro-oculograms (EOGs) Measure eye movement Electromyograms (EMGs) Measure muscle movement and have been used to distinguish between the stages of sleep.

How do we measure activity during sleep? Self-reports – keeping a record of sleep patterns and dreams. Useful for collecting information that could not be collected in another way. Accuracy? Observations – patterns and directions of eye movements can be recorded and related to stages. Noise and distractions can be controlled in sleep labs to increase reliability but they are artificial so reduce validity. Self-reports – keeping a record of sleep patterns and dreams. Useful for collecting information that could not be collected in another way. Accuracy? Observations – patterns and directions of eye movements can be recorded and related to stages. Noise and distractions can be controlled in sleep labs to increase reliability but they are artificial so reduce validity.

EEG Readings EEG readings are normally used, as frequency and amplitude differ depending on each stage.

Stages of Sleep Aserinsky and Kleitman (1953) divided sleep into 2 main classes: Slow Wave Sleep and REM Sleep.

Stage 1 A bit like deep relaxation, with lowered heart rate, muscle tension and temperature. It’s easy to wake people up. Alpha brain waves (frequency of between 8-12 cycles per second) Hypnogogic state – may experience hallucinatory images. A bit like deep relaxation, with lowered heart rate, muscle tension and temperature. It’s easy to wake people up. Alpha brain waves (frequency of between 8-12 cycles per second) Hypnogogic state – may experience hallucinatory images.

Stage 2 EEG shows slower and larger waves. Theta waves – 4-8 Hz Short bursts of high frequency sleep spindles. Little activity in EOG. K-Complexes – brains response to external stimuli (lasts about 20 mins) EEG shows slower and larger waves. Theta waves – 4-8 Hz Short bursts of high frequency sleep spindles. Little activity in EOG. K-Complexes – brains response to external stimuli (lasts about 20 mins)

Sleep Spindles and K-Complexes

Stage 3 Sleep deepens “descending the sleep staircase” EOG and EMG similar to stage 2 but EEG long, slow delta waves (1-5Hz) with some sleep spindles. Sleep deepens “descending the sleep staircase” EOG and EMG similar to stage 2 but EEG long, slow delta waves (1-5Hz) with some sleep spindles.

Stage 4 Largest, slowest waves of all, because it’s the deepest stage of sleep. Very hard to wake someone. Very little activity in EOG and EMG. Metabolic function is generally low but an increase in growth hormone. Sleep walking/talking and night terrors. Largest, slowest waves of all, because it’s the deepest stage of sleep. Very hard to wake someone. Very little activity in EOG and EMG. Metabolic function is generally low but an increase in growth hormone. Sleep walking/talking and night terrors.

REM Sometimes called paradoxical sleep. Low level EMG. Beta activity 13-30Hz Hard to wake someone but EEG shows brain is very active. Body is paralysed preventing us from acting out our dreams. Sometimes called paradoxical sleep. Low level EMG. Beta activity 13-30Hz Hard to wake someone but EEG shows brain is very active. Body is paralysed preventing us from acting out our dreams.

Dement and Kleitman (1957) 9 participants. 61 nights in a sleep laboratory. Showed similarity in their sleep cycles. 2 distinct kinds of sleep – REM and NREM which alternated during a night’s sleep. Average 92 min NREM and REM rhythm. When woken from REM sleep, dreaming was reported 79% of the time. When woken from NREM sleep, dream recall fell to under 7%. 9 participants. 61 nights in a sleep laboratory. Showed similarity in their sleep cycles. 2 distinct kinds of sleep – REM and NREM which alternated during a night’s sleep. Average 92 min NREM and REM rhythm. When woken from REM sleep, dreaming was reported 79% of the time. When woken from NREM sleep, dream recall fell to under 7%.

Contrasting characteristics of SWS and REM SWS Sensory information is restricted from entering consciousness by the thalamus. Helps to maintain sleep. Move towards conserving energy e.g. heart rate and blood pressure. REM Motor regions of the cortex stimulated. Why don’t we get up and walk around? Despite excitation of the motor cortex the motor neurons are inhibited. State of temporary paralysis, except the eyeballs!!!

Jouvet (1969) Found that the control of REM and NREM lies in the ascending reticular formation ( a network of millions of neurons buried deep in the brain).

How did he find this out? Jouvet used techniques such as lesioning and electrical stimulation of the brain.

Brain Structure Jouvet found control of sleep in two areas: Non-REM – Raphe Nuclei REM – Locus Coeruleus Jouvet found control of sleep in two areas: Non-REM – Raphe Nuclei REM – Locus Coeruleus

Neurotransmitters Jouvet also found that certain neurotransmitters were involved in different stages of sleep. Non REM – Serotonin REM - Noradrenaline Jouvet also found that certain neurotransmitters were involved in different stages of sleep. Non REM – Serotonin REM - Noradrenaline

Progress Check Quick Questions: 1.Summarise the four stages of SWS. 2.Give a limitation of using EEG recordings. 3.Summarise Dement and Kleitman’s study. 4.Summarise the differences between SWS and REM sleep. Quick Questions: 1.Summarise the four stages of SWS. 2.Give a limitation of using EEG recordings. 3.Summarise Dement and Kleitman’s study. 4.Summarise the differences between SWS and REM sleep.

Progress Check Stretch and Challenge Question: Are people responsible for crimes committed whilst sleep walking? Stretch and Challenge Question: Are people responsible for crimes committed whilst sleep walking?