SLEEP

Dement and Kleitman (1930’s) Qu. How do we measure sleep? Electro-encephalogram (Head) Electro-oculogram (Eye) Electro-myogram (Neck)

EEG TODAY

Brain Waves and Sleep Stages

Qu. What are the sleep stages? 1 2 3 4 5 6 7 Awake Hours of sleep REM EEG stages

Qu. What is different about infant and old people sleep patterns?

Qu. Why do we Sleep? Restoration Model = Sleep allows us to recharge our bodies and recover from fatigue Evolutionary/circadian rhythm model Sleep’s main purpose is to increase a species’ chances of survival Cognitive model = Sleep is necessary for the consolidation of memory and mental functioning.

Sleep deprivation experiments; Peter Tripp radio DJ sleep deprived self for 200 hours. Randy Gardner - sleep deprived for 264 hours under supervision of sleep researcher Dement

Sleep deprivation effects I.Q drop - about 60 studies have confirmed that one hours loss of sleep leads to a 1-point drop in IQ. Qu. If you skip two hours sleep a night for a week to cram in more revision, how many IQ points will you have dropped? 15 x points - your STM is very poor, you cannot think in complex ways and you loose your flexible thinking for creative answers - you are on auto-pilot.

REM Rebound - Dement Rebound phenomena Following sleep deprivation, we recover much of our lost sleep but there is some segregation of recovery of different types of sleep. Following selective SWS or REM deprivation, there is selective recovery

RESTORATION OR ADAPTION? Jim Horne (1999) asks…… Qu. If the body can repair itself under a wakeful state, what is the main purpose of sleep, physiological repair or neurotransmitter recovery? Qu. If REM is for neurotransmitter recovery, why do infants spend 50% of their sleep in REM, but by the first year they have half of that (when most learning occurs)?

RESTORATION THEORIES? Horne (1999) - asks; Qu. What is the point of falling unconscious? Qu. Is sleep is purely restorative, why are there so many variations of sleep patterns across species?

Evolutionary/circadian rhythm model Sleep’s purpose = increase the chances of survival Species sleep patterns are different due to…. BRAIN DEVELOPMENT BODY SIZE Ecological niche

Qu. Can you explain these differences? Qu. Do all animals sleep? Mammal Hrs of sleep/day Giant Sloth Tree Shrew Cat, Hamster Mouse, rat, squirrel Hedgehog Humans, rabbit, pig Cow, Goat, Elephant Horse, Roe deer 20 15 14 13 10 8 3 2 All mammals and birds sleep. Qu. Can you explain these differences?

Qu. Do whales sleep? Apparently so

Fish, reptiles and amphibians have periods of ‘inactivity’ Qu. Do fish sleep? Apparently so Fish, reptiles and amphibians have periods of ‘inactivity’

SWS and REM sleep patterns in mammals

Meddis, (1975) - Predation theory Sleep has evolved to help species adapt to threats. Patterns of sleep diversify across species due to environmental threats posed, leading to; Sleep pattern? Large predators = Small vulnerable animals = Animals who cannot see in the dark =

Lions can do little else but sleep for up to 2 x days after a large kill

Webb, (1982) - Hibernation theory Sleep evolved to conserve energy Hibernation necessary when food resource are low.

Qu. What would happen to the sleep patterns of animals who can function at night?

Qu. What would happen to sleep patterns of animals who can’t hunt at night?

Energy consumption issues? Marine mammals do not show REM sleep, perhaps because relaxed muscles are incompatible with the need to come to the surface to breathe. In dolphins and birds, only one brain hemisphere enters SWS at a time— the other remains awake.

Evolutionary critiques? Qu. Can these ideas be tested? Qu. Does sleep serve the same function for all species? Qu. Is sleep an ‘adaptive process’? Qu. What happens if we are deprived of sleep?

COGNITIVE THEORIES Empsom and clark (1970) Sleep - especially REM sleep - facilitates the reinforcement of information in memory. Qu. What would happen if you were deprived of REM sleep during revision? Qu. How would you prove the theory right?

REM and COGNTITION Cortex hippocampus Strickgold (1999) found that PET scans reveal a high level of activity between these two structures during sleep. SWS - activity is one way REM - info flows other way

Strickgold (1999) Method: Students taught a visual discrimination task (learning to spot things in their peripheral vision). They had to do 25 sets in the evening, and another 25 sets in the morning - measured overall improvement. Some were allowed to sleep normally, others were sleep deprived - some SWS, others REM sleep. Results: Normal sleep - improved performance 40% Deprived SWS sleep - Improved 28% Deprived REM sleep - improved only 18%

CONCLUSION?