The origin of biological clocks | Science News
(Note: Carrying our sleep research on student sleep patterns seems to be as valid as research on the sleep patterns of cats).
Other evaluation points
When we lose sleep and are given the opportunity to make it up we only catch up on a small proportion of it. This suggests that not all sleep is needed. Why therefore would we need non-essential sleep?
Amino acids are not stored in the body and only remain in the bloodstream for about eight hours before being broken down or excreted. As a result we would expect protein synthesis to stop half way through a night’s sleep. This would explain why deep sleep occurs in the first half of a night’s sleep. Of course this also assumes that we eat just prior to going to sleep!
Oswald (1980) and Hartman (1984) built on the theory to include restoration during REM sleep. They believe that REM is for restoration of the brain. Stern & Morgane (1974) believed that neurotransmitter levels within the brain may be restored during REM sleep. The young brain is growing and developing at its fastest rate so young children, especially babies sleep for much longer than adults. In the newborn about 9 hours a day is spent in REM compared to about 2 hours in adults.
Note: restoration theories of sleep make cognitive sense since we suffer so many unpleasant consequences when deprived of sleep
It is important to remember that this seeks to explain the biological state of REM sleep and makes no mention of the psychological state of dreaming. Therefore it is not to be used in a question that asks for theories of dreaming.
Research in support of restoration theories
The most obvious support comes from aspects of the sleep deprivation studies to be discussed in the next section. First some other evidence:
The Tick-Tock of the Biological Clock - Scientific American
Tying all of this together (wall to wall AO2)
Insomnia is a complex disorder and probably results from an interaction of many factors. Spielman and Glovinsky (1991) suggest the predisposing, precipitating, perpetuating model to explain the onset and maintenance. This is similar to the diathesis-stress model we saw in abnormality at AS but takes it a crucial stage further… let me explain:
Predisposing: refers to the genetic or biological component or any other underlying issue such as personality which makes the onset of the disorder more likely.
Precipitating: refers to factors that trigger a period of insomnia. This could be environmental such as uncontrollable noise or a hot spell in the summer. It could be a period of physical illness perhaps resulting in pain or in need of medication. More likely it will be a period of stress or anxiety.
In addition insomnia requires a perpetuator, since the insomnia usually continues long after the precipitator has been sorted out.
Perpetuating: During the insomnia patients have suffered anxiety due to inability to sleep and have learned to associate various nighttime habits and even the bedroom and the bed itself with sleeplessness. After the stress has been lifted this negative association still exists and as a result so does the insomnia.
Treatments for insomnia usually concentrate on the perpetuating factors and attempt to improve sleep hygiene. Often insomnia leads to habits that create poor sleep hygiene. Inability to sleep at night often results in patients taking afternoon naps to compensate. Tiredness results in less exercise and patients often resort to alcohol to help trigger sleep. All of these need to be discouraged to improve hygiene and help break the perpetuating cycle.
Sleeping pills (usually benzodiazepines) that were so popular in the seventies are no longer prescribed in such massive numbers. Patients become dependent on the drugs and suffer even worse insomnia when they stop taking them.
Apnoea (properly obstructive sleep apnoea (OSA)) is brief pauses in breathing resulting in a suspension of the movement of gases between the lungs and the air. This is brought about by a blockage preventing oxygen entering the lungs. NB: Gaseous exchange within the alveoli of the lungs and cellular respiration continue as normal. This reduction of air movement is called hypopnoea).
Clinically speaking, apnoea occurs when breathing ceases for ten seconds or more at least ten times per hour and results in a drop in blood oxygen saturation and/or a 3 second or greater alteration in the EEG (electro-encephalogram). Apnoea is not an issue during waking hours since there is sufficient muscle tone to keep the air passages open.
The brain, aware of the drop in oxygen levels wakes the person to unblock the obstruction and this waking is often accompanied by a loud snore!
Apnoea can be relatively mild or severe. The level is assessed using the API (apnoea/hypopnoea index) which does exactly what it says on the tin… it measures the number of apnoeas and hypoapnoeas per hour. Fewer than ten such events per hour is likely to cause few problems and will probably go unnoticed by the patient.
Diagnosis and assessment of severity often requires an overnight stay in hospital with the patient attached to a polysomnograph. This measures EEG, EMG, chest movements, airflow through the nose and mouth, pulse rate and blood oxygen levels…oh yes and often video footage of the patient snoring and waking!
Anything that restricts airflow through the throat can cause OSA.
Pretty much as you’d expect: these include tiredness and deficits in cognitive functions. Macey et al (2002) believes that repeated starvation of oxygen causes damage to the neurons of the brain.
Childhood OSA can result in an inability to concentrate, poor memory and attention span and lowered IQ as well as poor performance at school.
Being a morning or an evening person is partly dependent on your own internal clock. Take this quiz to see if you are classified as a morning or evening person. Developed for the 2000 Holiday Lectures on Science, Clockwork Genes: Discoveries in Biological Time.