Supercharismatic nucleus(SCN) is the pacemaker of the sleep wake cycle Generates its own biological clock via protein synthesis It is connected to the optic chiasm so receives input about the light levels which also regulates the rhythm(exogenous zeitgebers) It is connected by neural pathways to the pineal gland, so electrical stimulation of the SCN is passed to the pineal gland causing it to release melatonin Melatonin is inversely proportioned to light Melatonin influences the production of serotoninA Accumulates in the raphe nuclei in the hindbrain, near the pons, and stimulates the shutting down of the RAS (reticular activating system), This is closely linked with brain activity. So serotonin could be the switch to start sleep.

Noradrenalin accumulates in the locus coeruleus in the pons and if this area is damaged, noradrenalin levels fall and REM sleep is impaired. This led him to conclude that different areas of the brain and the corresponding neurotransmitters controlled the two types of sleep, NREM and REM. The raphe nuclei and its serotonin pathway controls NREM sleep; the locus coeruleus and noradrenalin pathway control REM sleep. Noradrenalin is also a biochemical involved in the nature of sleep, linked with REM Sleep The nature of sleep is more so complex More neurotransmitters than just serotonin and noradrenalin e.g. Acetyl choline are involved Debate about the function of adenosine(builds up during day and broken down during the night) suggests that it causes drowsiness preparing our brains for sleep

Stage 115mins – EEG = alpha waves EOG = slow rolling eye movements EMG = reduced muscle tension Stage 220mins – EEG = theta waves, spindles and K complexes EOG = little eye movement EMG = muscles relaxed Stage 315mins – EEG = delta waves, spindles EOG and EMG are the same as stage 2 Stage 430mins – EEG = delta waves(SWS) EOG and EMG show very little activity Stage 510mins – EEG = beta waves, very active(REM) EOG = rapid eye movement EMG = paralysed

Cycle 11,2,3,4,3,2,5 Cycle 22,3,4,3,2,5 Cycle 32,5 Cycle 42,5 Cycle 52,5 EEGs EOGs EMGs have been used to distinguish the stages and cycles of sleep. EEG readings are normally used to distinguish the sleep stage as the frequency and amplitude differ depending on the stage. Artificiality of the sleep laboratory. A significant weakness is that such physiological measures are gathered in a sleep laboratory, where the artificial conditions and the fact that research participants are wired up to machines may affect sleep patterns. The sleep laboratory is reductionist as it does not reflect the range of factors that can influence sleep in real life. The research lacks mundane realism and as a consequence the findings may lack generalisability to real-life sleep patterns and so ecological validity may be lacking. Consequently, the meaningfulness of the findings may be limited.

By determining the effects of sleep deprivation we can begin to look at functions of sleep and therefore the nature of sleep The individual experiences constant wakefulness Limited research has been done large scale due to the lack of volunteers Case studies are the most common research method Stayed awake for 8 days The effects of this included delusions and hallucinations Stayed awake for 11 days Effects included disorganised speech, blurred vision, and a small degree of paranoia

Meta-analysis by Hüber-Weidman reviewed sleep-deprivation studies Common effects of sleep deprivation(6nights). Distress, a strong desire to sleep, periods of micro-sleep, delusions 6 th night, “sleep deprivation psychosis” depersonalisation, loss of identity, and difficulty in coping with environmental demands and other people Showed that rats also die if deprived of sleep for over 4 weeks. other effects included overeating Man who had brain damage, couldn’t sleep and couldn’t function and eventually died Rare condition. Person stops sleeping at middle age and dies within 2 years SHOWS HOW IMPORTANT PARTS OF THE BRAIN ARE TO SLEEP SUGGESTS THAT GENES MAY HOLD A PREDISPOSITION TO INSOMNIA UNIVERSAL EFFECTS OF INSOMNIA SUGGEST MORE BIOLOGICAL CAUSE THAN PSYCHOLOGICAL

Reduction in the normal amount of sleep, or reduction in a particular type of sleep (REM/NREM) REM sleep deprivation in cats. Cats were placed on a flowerpot in a tank of water. They were able to sleep without falling off during NREM but fell off as soon as they entered REM due to the loss of muscle tone during the paralysis of REM sleep. Continued REM deprivation proved fatal. Deprived participants of either NREM or REM sleep to test the difference in the effects REM deprivation = severe (increased aggression and poor concentration) Greater need to catch up on this attempts to enter REM sleep doubled Sleep - normal the participants spent much longer than in REM sleep = REM rebound effect

Participants could reduce their total night’s sleep by 2 hours and reported feeling fine. Follow-up study participants gradually reduced their total amount of sleep over a period of 2 months, At the end they slept for only 4 hours per night and reported no adverse effects. Rats suffered physiological distress when partially deprived of sleep, breakdown of normal bodily controls

Sleep is to repair and recharge the brain and body through restoring energy resources, repair and growth of tissue cells and muscles, and replenishing neurochemicals. Oswald NREM and REM have different functions NREM – restores bodily processes REM – renews brain processes through protein synthesis Horne distinguished between core(stage 4 + REM) and optional(1-3) core is needed to replenishing the brain processes and replenishing the body can happen during relaxed wakefulness Only really need 5 hrs of sleep the rest is optional Sleep is adaptive serving the purpose of survival If it wasn’t adaptive then we would of expected it not to exist now Meddis sleep for protection, as we cannot perform normal tasks like that during the day therefore being immobile keeps us safe from predators Seigal sleep is used for energy conservation true of small mammals who have a high Volume : Surface area

Growth hormone is released during stage 4, which is needed for protien synthesis during body repair = support for Oswald NREM responsible for restoration of the body High brain activity during REM sleep(EEG) is support for the replenishing of the brains processes Babies’ sleep patterns are consistent with REM as a source of restoration(2/3 of the day is sleep, 8hrs being REM) = larger amount of activity in the developing brain linked to protien synth, needed for synaptic growth Patients how survive drug overdoses and patients who have extensive ECT = increase in REM(6-8 weeks the same time needed to replace half the brain protien) Randy Gardner slept for 15 hours. He recovered only about 25% of overall lost sleep, but 70% of stage 4 was recovered and 50% of REM. This is known as the (REM) rebound effect = support for Horne that stage 4 and REM are core sleep Research suggests that new neurons are in fact generated, for example in the hippocampus, during sleep, facilitated by exercise, unless this neurogenesis is blocked by stress or sleep deprivation and so supports the ideas of restoration through regeneration of the cells.

Shapiro et al. People who completed an “ultra marathon” of 57 miles slept about an hour and a half longer for 2 nights following the marathon, which supports restoration theory. Stern & Morgane - Restoration of the brain during REM sleep may rebalance the neurotransmitters = people on antidepressants show decreased REM = due to the fact that the drugs increase neurotransmitter levels therefore less need for REM sleep. Horne & Minard - we would expect increased activity to necessitate more sleep. F: participants exhausted by high activity fell asleep faster but not for longer, which contradicts Shapiro et al.’s (1981) findings.

Rechtstaffen Showed that rats also die if deprived of sleep for over 4 weeks. other effects included overeating Therefore the effects of sleep deprivation show that it is necessary for survival Allison et al. F: body size aren’t the only factors determining sleep, food quality is also a factor Predator/prey sleep patterns. The difference in predator/prey sleep patterns provides evidence that evolutionary forces are at work as predators (lions, tigers, etc.) sleep for much longer periods than prey (cattle, etc.). Metabolic rate and energy conservation support Siegel’s theory. Smaller animals such as squirrels and shrews sleep for much longer periods of the day than do larger animals. This is due to their high metabolic rate so sleep is a way of conserving energy, supporting Siegel’s theory. Further evidence is that cows sleep for only 3 hours per day because they have a low-energy diet, and so have little energy to conserve during sleep, and need to stay awake to eat.

Lack of energy conservation. Sleep provides little more energy conservation than behavioural inactivity According to Meddis sleep is for protection so we would expect sleep to be inconspicuous. However humans are loud sleepers and much research as gone into finding a cures to snoring

Human infants vary in their sleep patterns and do not have a set pattern at birth. =Brain is immature at birth, so the development of the rhythm could well be in line with early brain development and growth. Frequent night awakening is most common in babies from 4 to 12 months = their increasing knowledge that being awake is more interesting than being asleep = they have an increasing awareness that they are being separated from their primary caregiver Whatever the variations in baby and child sleep patterns, it is generally true that younger people sleep more than older ones. Babies = 50% of their sleep is in REM. Young adults = 20% of sleep in REM Elderly adults = 15% in REM.

Studied night waking in 100+ infants F: 3 months 46% were waking, 6 months 39%, 9 months 58%, 12 months 55%. The increase at 9 months and this could relate to the socio-emotional factors such as separation anxiety

One key change in sleep with age is the decrease in slow-wave sleep. Takes place twice, between 16 and 25 years and 35 and 50 years. It is not just the decrease in sleep that is the issue but the decrease in growth hormone and consequently growth and repair are also slowed. 149 healthy adult males(16-83 yrs old) Tracked over 14 years F: Loss of 27 minutes’ sleep per decade, little growth hormone, men over 45 years who had very little slow-wave sleep at all. Linked to a loss of muscle mass and the ability to exercise plus a tendency to obesity. A meta-analysis of 65 studies representing over 3500 healthy participants F: total time asleep and the percentage of slow-wave and REM sleep declined with age: whilst sleep latency and % of stages 1 and 2 sleep increased with age.

This napping in elderly people has been positively correlated with excessive daytime sleepiness and with depression.