P SYCHOBIOLOGY OF A LTERED S TATES OF A WARENESS S LEEP (Text reference – pages 164 – 177)

Measurement of Arousal Level Electro-encephalogram (EEG) measures brain waves from the scalp coming from the cerebral cortex of the brain. Measurements are in cycles per second (cps) – also known as Hertz (Hz) Low Arousal Medium High Arousal

Measurement of Sleep - Polysomnography Psycho-physiological Measures 1. Electro-encephalogram (EEG) measures electro-cortical activity (“brain waves”) 2. Electro-oculogram (EOG) measures eye movement activity electrically 3. Electro-myogram (EMG) measures tonic muscle activity These three measures can determine the conventionally defined different states and stages of sleep.

See figures 5.10 & 5.11 (page 165)

Lack’s Sleep Laboratory

Michael Gradisar, PhD student, watching Flinders Sleep Lab PSG computer Deep Sleeper

Is 8 hours of solid sleep the ideal?

Sleep is more like a Roller Coaster Ride See Figure 5.12 on page 166

Perceptual Awareness during Sleep? Charles Shultz recognised an increasingly common phenomenon. Sleep blocks perceptual awareness. Learning during sleep is not possible. Students can fall asleep in class despite scintillating lessons.

Snoopy is entering which stage of sleep? A cat begins sleeping with its head upright and its paws underneath. But soon the cat drops on its side and its head rests on the floor. What do you think is happening to cause the change in position?

You may be surprised to learn that sleep-walking, or somnambulism, typically occurs during slow-wave sleep rather than REM. Why would sleep-walking be unlikely during REM? Lighter_side.html

1. Deep sleep (S4) decreases with age. 2. Light sleep and awakenings increase.

Sleep Homeostasis The longer one is awake and deprived of sleep, the stronger is the sleep drive or sleep propensity. The longer one is asleep, sleep drive lessens and sleep propensity reduces. Sleep homeostasis operates similarly to other drive mechanisms such as hunger/food (body weight is homeostatically controlled), thirst/water (hydration is maintained), temperature is regulated, etc. The “set point” for sleep is about 33% on the average or 8 hours out of 24. Water bucket analogy - The bucket steadily fills up with water while awake. Falling asleep opens a valve at the bottom and reduces water pressure, fast at first (deep sleep) and slower as the water reaches bottom (light sleep).

What is the effect of total sleep loss? World record is 11 days & nights. continuous increase of sleep propensity and fatigue deficits in performance tasks that require sustained attention over long periods (probably from micro-sleeps) no deficits in short duration, challenging tasks some emotional fluctuation hallucinations? probably REM sleep onset. Recovery sleep is longer than normal (3-5 hours longer on the first night and 2-3 hours longer on the second). Recovery sleeps bring a return to normal functioning despite not paying back the total sleep debt.

Can we get by on 6-7 hours sleep? Experiments have shown that after a few days, there is no further increase in subjective sleepiness. However, deficits on performance measures of attention continue to climb with continued restricted sleep. The “post-lunch dip” of alertness becomes prominent. General productivity probably suffers over the 18 hours of wakefulness. Is the extra two hours of wake time available counter balanced by less efficient behaviour when awake? Some suggestion that sleep restriction produces a mild stress. However, the greatest risk to health is probably not disease but falling asleep at the wheel of the car. Australian sea lions on Kangaroo Island seem to manage the feast to famine diet of fish which is opposite to the famine to feast on sleep.

Conclusions Sleep can be measured with polysomnography. Sleep states (eg. REM) were discovered and NonREM sleep was divided up into four stages by depth. The psychophysiology of REM sleep is very different than NonREM Sleep is not a constant state but more like a roller coaster with peaks spaced about 90 minutes apart. Deep sleep is prominent in the first 3-4 hours of the sleep period while lighter sleep and REM sleep is prominent later. Sleep is governed by a homeostatic mechanism. With aging depth of sleep decreases but does not impair daytime functioning. Sleep can be deprived or restricted but at the peril of overwhelming or insidious sleep propensity.

Written Summary You have been given a range of newspaper and journal articles relating to sleep to help broaden your understanding of the psychology of sleep. Remember that your text book has excellent information on pages Write a summary of “The Psychology of Sleep”. You may like to focus on a particular aspect such as –The stages of sleep in a typical night –Psychophysiology –How much sleep is enough? –Explaining your own pattern of sleep. You have two lessons to complete this