Sleep

C81BIO – Lecture 12

Dr. Mark Haselgrove

Overview of the lecture

(1)Measurement and stages of sleepPhysiological correlates of sleepSleep cycles and REM

(2) Theories of SleepComparative analysis of sleepEffects of sleep deprivation

(3) Areas of the brain involved in sleepHypothalamusReticular System

(4) Sleep DisordersNarcolepsyREM sleep without paralysis

(1) Measurement and Stages of Sleep

Three principle measures of sleep:

(i) Electro-encephalogram (Head)(ii) Electro-oculogram (Eye)(iii) Electro-myogram (Neck)

(1) Measurement and Stages of Sleep

Four stages of Sleep EEG:

Pre-sleep Alpha waves

Bursts of 8- to 12-Hz activity inlow-amplitude/high-frequency waves

Progressive: increase in amplitude decrease in frequency

Sleep Spindle – 1 to 2 s burst of12- to 14-Hz waves

K complex – Single large upward, then downwards deflection

(2) Theories of Sleep

Recuperation theories

- Being awake disrupts homeostasis

- Sleep restores this

e.g. sleep restores energy levels

Evolutionary theories

- Sleep is NOT a reaction to homeostatic disruption

- Sleep evolved (in humans) to prevent accidents and predation at night

- Sleep is like sex. We don’t need it to stay alive, but we are still motivated to have it!

(2) Theories of Sleep - Analysis

Sleep in animals

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. Fish, reptiles & amphibians have periods of inactivity too

- Large species differences in sleep: Not related to body size/ temperature

- Sloths hardly move, yet need 20 hrs/day

- Little/no Effect of exercise on sleep duration in humans (Youngstedt & Kline, 2006)

(2) Theories of Sleep - Analysis

Sleep in animals

- Not consistent with recuperation theories of sleep

- Evolutionary theories - Sleep related to: How vulnerable you are asleep Time spent eating/day

Lions can do little else but sleepFor 2 days after a kill

(2) Theories of Sleep - Analysis

Effects of sleep deprivation - Humans

- Recuperation theories predict that with sleep deprivation:

(1) Increases in physiological/behavioural disturbances(2) After deprivation, missed sleep must be regained

- Deprivation influences: Mood, physiological function,molecular function (Cirelli, 2006)

- Effects on Executive function: Assimilating changing informationUpdating plansReference memory(Curcio et al., 2006)

X

- But, people recover well after sleep deprivation (Dement, 1978):Randy Gardner – 260 hrs awake: 1st recovery night 14 hrs sleep

Then back to normal

(2) Theories of Sleep - Analysis

Effects of sleep deprivation - Humans

- REM sleep deprivation

- Preventing REM sleep makes the body want it more. (Webb & Agnew, 1967)

- Deprivation of REM sleep causes a transient rebound. (Brunner et al 1990)

- No cognitive or emotional effects however.

(2) Theories of Sleep - Analysis

Effects of sleep deprivation - Animals

- After several days, experimental rats died

- But, post-mortem revealed swollen adrenal glands, gastric ulcers and internal bleeding

- Result a consequence of stress and physical damage??

(3) Areas of the brain involved in sleep

(i) Hypothalamus

Studied the brains of those who had died from the virus encephalitis lethargica

- Victims who had difficulty sleeping: Damage to anterior region

- Victims who had difficulty staying awake Damage to posterior region

Constantin von Economo

Confirmed in lesion studies with animals (Saper et al., 2001)

(ii) Reticular System

(3) Areas of the brain involved in sleep

- Bremer (1936)

Cerveau isole transection = slow-wave sleep pattern

Encephale isole transection = Normal sleep-wake cycle

Thus, “wakefulness” area = somewhere in-between the two

- Mouzzi & Morgan (1949)

Stimulation of the reticular formation of sleeping cats woke them up.

(ii) REM sleep without core muscle atonia

(i) Narcolepsy

(3) Sleep Disorders

Relatively brief periods of sudden sleep

I was a halfback playing football, and after the quarterback received from the centre, he passed it to me and I’m supposed to go around and then cut back in. As I cut back in there is this big 280-pound tackle waiting so I, according to the rules, shoulder barged him…..

When I came to I was standing in front of our dresser and I had gotten out of bed and run and knocked lamps, mirrors and everything off the dresser, hit my head against the wall and my knee against the dresser

- Schenck et al. (1986)

Reading

Pinel, J. P.J. (2011) Biopsychology, Pearson. Chapter 14

Carlson, N. R. (2010) Physiology of Behavior, Allyn & Bacon. Chapter 9

Kalat, J. W. (2011) Biological Psychology, Thompson. Chapter 9

Next Time: Schizophrenia & Depression. In: Phys B1

Email: Mark.Haselgrove@nottingham.ac.uk