Area of study Three States of consciousness

1. Area of study ThreeStates of consciousness Sleep Chapter 8

2. Sleep: a regularly occurring altered state of consciousness that typically occurs spontaneously and is primarily characterised by a loss of conscious awareness. • FACT #1: Over a lifetime, we spend about 1/3 of our time asleep. If you live to 75 yrs that’s 25 yrs worth of sleep!

3. METHODS USED TO STUDY SLEEP • Sleep Laboratories • -areas often attached to hospitals where patients with sleeping disorders can be diagnosed and treated • -typically set up as little bedrooms • -patients or research participants can be woken at various stages to describe particular experiences

4. Sleep labs cont. • Lab fitted with a number of devices to monitor and record various physiological responses during the night • Advantage: measurements can be made without waking the person

5. EEG: device that detects, amplifies and records the electrical activity that is spontaneously generated by the brain (brain waves)-Different patterns indicates different stages of sleep • Electroencephalograph (EEG)

6. Electromyograph (EMG) • EMG: device used to detect, amplify and record the electrical activity of the muscles • -enables measurement of muscular tension, tone & activity

7. Electro-oculogram (EOG) - EOG: is a device for measuring eye movements or eye positions by detecting, amplifying and recording electrical activity in eye muscles that control eye movements

8. STAGES OF SLEEP • Over a course of a typical nights sleep, we experience two distinct states of sleep. • -NREM sleep: non rapid eye movement sleep • -REM sleep: rapid eye movement sleep • They occur in a continuous cycle, with one following the other.

9. In adults, one cycle of NREM sleep lasts about 70-90 mins, and consists of four distinct stages. • A period of REM sleep follows each period of NREM sleep. The time we spend in REM sleep tends to increase as the night progresses.

10. Generally, a complete sleep cycle lasts from 80-120 mins, and we go through this cycle approx. 4-5 times across 8 hrs of sleep.

11. NREM SLEEP • Approx. 80% of sleep time is spent in this stage • The first half of the night has more NREM sleep than the second half • During NREM, the brain is active, but not as active as during REM sleep/NWC.

12. Body undergoes recovery; repairing body tissue, removing wastes and replenishing neurotransmitters • Fact #2: Research has shown that after a day of strenuous physical activity, an individual will spend more time than on average in NREM sleep.

13. Four different stages • Sleeper progresses from the lightest stage of sleep to the deepest stage, and back again to the lightest stage • Every stage of sleep is identifiable by a distinct brain wave pattern

14. Each brain wave can be distinguished by the number of brain waves (frequency) and the intensity of the brain waves (amplitude) • Low frequency= slow brain wave activity troughs=low amplitude • High frequency= fast brain wave activity peaks=highs amplitude

15. When we fist go to sleep and begin to relax the brain emits alpha waves • Alpha waves: high frequency and medium amplitude waves. • Tip: alpha=awake!! • The transition period from being awake to asleep is referred to as a hypnogogic state • Characterised by slow rolling eye movements. 1-2 mins long. May experience flashes of colour, feelings of floating, jerks, dreamlike images, sense of falling

16. NREM STAGE 1 • Occurs when we drift in & out of true sleep • Lose awareness of self & surroundings, but are aware of faint sounds • Physiological changes: lower level of bodily arousal (decreased heart rate, respiration & muscle tension) • Duration: 5-10mins

17. NREM STAGE 1 • Brain waves: decrease in alpha waves and production of theta waves. • Alpha= high frequency, medium amplitude • Theta= irregular medium frequency, high & low amplitude

18. NREM STAGE 1 • Special characteristics: • -hypnic jerk: when part of the body goes into a spasm, as a result of the muscles relaxing • -if woken from this stage, we may deny having been asleep at all!

19. NREM STAGE 2 • -Light stage of sleep • - point at which “we are are truly asleep” • Body movements lessen, breathing becomes regular, blood pressure and temperature fall & heart rate decreases further

20. NREM STAGE 2 • Lasts for about 10-20 min • Brain still responds to both internal & external stimuli • About half way through this stage, we are only responsive to loud or strong stimuli, which indicates a deepening sleep • Response is indicated by the appearance of K-Complexes

21. K-Complexes: low frequency, a slightly higher amplitude waves that occur in response to a stimulus • Brain waves: mainly theta waves, but lower in frequency and higher in amplitude than the theta waves in stage 1. Appearance of sleep spindles, which lasts for one second.

22. NREM STAGE 2 • Special characteristics: • -sleep spindles: brief bursts of high frequency brain waves. Last for one second and indicate when a person is truly asleep • -k-complexes • -still easily aroused from this stage • -People often say that they were only dozing or thinking

23. NREM STAGE 3 • Start of the deepest stage of sleep • Best called moderately deep sleep • Lasts for about 10 mins • Physiological processes continue to decrease • Extremely relaxed & unresponsive to external stimuli

24. NREM STAGE 3 • Reduction in brains electrical activity • Brain waves: delta waves appear. Make up 20-50% of brain waves recorded during this stage. • Delta=lower in frequency & higher in amplitude

25. NREM STAGE 3 • Special characteristics: • - slow wave sleep (SWS): marked by the appearance of delta waves • -generally begins within an hour of falling asleep & continues for approx 30 mins • -difficult to wake ppl & when awoken ppl report feeling groggy & disorientated

26. NREM STAGE 4 • When delta waves make up more than 50% of the EEG reading, ppl have moved into stage 4. • Very deep sleep • Physiological signs are similar to stage 3; however, muscles are so relaxed that we barely move

27. NREM STAGE 4 • In the first cycle of sleep, a person may spend 20 mins in this stage • but as the night progresses, ppl spend less and less time in stage 3 & 4. • Brain waves: delta waves dominate & are even slower & larger than those in stage 3

28. NREM STAGE 4 • Special characteristics: • - extremely difficult to wake • -will take up to 10 min to re-orient themselves if woken in this stage • -This is referred to as sleep inertia or drunkenness

30. NREM STAGE 4 • Special characteristics: • -stage may not occur at all in the sleep cycles close to the morning • -this has led to the belief that sleep before midnight is the most beneficial and rejuvenating • -sleep phenomena such as sleep walking, sleep talking & night terrors occur

31. NREM SLEEP • An individual will progress through the first 4 stages of sleep (NREM) in 45-60 min before regressing back to stage one again • Once the first full NREM cycle is complete, our body begins to respond as though we are waking up. This is a sign that we are waking up.

32. REM SLEEP • Period of rapid eye movement (REM): eyeballs move rapidly back & forth beneath closed eyelids • Body’s internal functioning is more active & less regular than in NREM • Heart rate is faster, blood pressure rises and breathing is quicker • However, sleeper is totally relaxed

33. REM SLEEP • May be some small muscle twitches in the face, fingers, toes but otherwise skeletal muscles are limb • Body shows few outward sign of movement: Paradoxical sleep • Paradoxical sleep: internally brain & body active, while externally the body appears calm & inactive

34. REM SLEEP • Although not known for sure, researchers believe that this paralysis stops us from acting out our dreams • Most dreaming occurs in REM • If woken during this stage, sleepers report having been dreaming 80% of the time • All ppl dream several times a night, although we may recall that we didn’t dream!

35. REM SLEEP • Dreaming also occurs during NREM, but is less frequent, less vivid, & less memorable. • Eye movements are unrelated to the content of dreams. • Some researchers believe that they are simply physiological movements that occur in response to random neural firing in the brain

36. REM SLEEP • However, the specific reason for the eye movements is still unclear. • A REM cycle occurs that occurs early in the night may only last a few mins, while a later REM period may last for up to an hr.

37. REM SLEEP • Brain waves: irregular, consisting of beta waves. • Beta: high frequency, low amplitude; similar to those produced during NWC.

38. REM SLEEP • Special characteristics: • -Paradoxical sleep • -some researchers believe that sleep plays an important role in assisting us with storing memories by strengthening newly made connections • -while unsure about the exact purpose of REM sleep, researchers believe that it serves some biological purpose.

39. REM SLEEP • Sleep characteristics: • -as demonstrated by individuals who catch up on missed REM sleep by increasing the time spent in this stage over subsequent sleep cycles. • -Possibly, REM sleep plays a role in the maturation of the nervous system.

40. STAGES OF SLEEP • Sleep cycles are highly individual & variable • A poor sleeper may spend less time on average in stage 4 and REM sleep • The amount of time spent in each stage of sleep also varies across the lifespan • Infants & children spend significantly longer period of time in REM sleep than adults