Psychology Paper 3 Notes:
Biology of Sleep
Biological rhythms:
Regular patterns of physiological, behavioral, or cognitive activity. They are divided into:
Circadian
= biological rhythms with a cycle length of 24 hours.
Example: body temperatures in humans & the sleep-waking cycle
➔ It makes sense for the body’s physiological processes to be turned into the
sleep-waking cycle so that energy is provided when needed.
➔ The Suprachiasmatic Nucleus (SCN) and the pineal gland in the brain control this
important biorhythm.
◆ The SCN is situated in the hypothalamus and has an inbuilt rhythm.
◆ The SCN is directly linked to the retina in the eye
◆ So, light activity affects the SCN, which regulates the circadian rhythm
Key Study: Siffre (1975)
Procedure:
- He spent 6 months in an underground cave with no access to natural light
- With the absence of this critical zeitgeber, biological rhythms become what is
called free running (a term used to describe biological rhythms in the absence of
external zeitgebers)
- The cave was artificially lit and could be turned on or off depending on whether he
was sleeping or awake, on his command
- He could sleep and eat when he wanted to
- A variety of psychological functions were recorded, including body temperature,
heart rate, blood pressure, and of course his sleep and waking cycle.
Key findings:
- Siffres's waking circadian rhythm extended from the normal 24 hours to between
25-32 hours - meaning his days became longer.
- When it was time for him to leave the cave, he thought he was only on the 151st
day rather than the 179th.
- His body temperature circadian rhythm was more stable. It only extended to 25
hours.
- One outcome of this was that his sleep-wake cycle became
desynchronized from his body temperature rhythm.
- In the absence of environmental zeitgebers such as light, our endogenous
pacemakers or body clocks can still regulate biological rhythms. However, this
regulation is not perfect, so the rhythms are not perfectly turned into the 24-hour
, cycle.
This study suggested that humans use natural light (exogenous zeitgebers) to regulate a
24-hour circadian sleep-wake cycle, demonstrating the importance of light for this
circadian rhythm.
Cons: Pros:
- Methodological issues: This was - Study support: a study on Aschoff
only done once, and only on Siffre. and Wever found that the
Therefore, the information can only sleep-waking cycle of the students
be generalised and taken with was kept in an underground bunker
caution. with similar conditions of Siffre.
- Caused ethical issues: he suffered Although the general picture is
from depression. It can't be done supported, it can't be generalized,
again. and also, these students weren't in
the cave for as long as Siffre was.
Key case study: Stephen and Zucker (1972)
Procedure:
- They investigate the effects of a damaged SCN on circadian rhythms.
- There were two controlled groups of rats in the laboratory
- The first group had a controlled routine where they were given 12 hours of
light followed by another 12 hours of darkness.
- The other group was the group with the broken SCN
- They recorded the amount of water they drank and the level of activity they
performed
Findings:
- They found that the control group had higher levels of activity and water
consumption than the group with the broken SCN. This is because they believe
that damage to the SCN eliminates the normal circadian patterns of drinking and
activity.
- They concluded that the SCN is one of the key pacemakers in the brain controlling
circadian rhythms.
Cons: Pros:
Methodological issues: Controlled study:
- Stephen and Zucker also damaged - Unlike Siffre’s study, this one was a
other parts of the hypothalamus to more scientific and controlled study
show that this did not affect of endogenous pacemakers. And
circadian rhythms. However, the because it was done on a rat, it
surgical method that was used was easier to control and monitor
caused 11 out of the original 25 to than if it were to be done on a
survive. There is still a possibility human.
that the severity of the operation
might have affected the rat's
behavior.
- The study also used rats, which
raises the issue of the lack of
generalizing from rats to humans.
, That is why it can only be
confirmed if the study was done on
humans
Infradian
= biological rhythms with a cycle length of more than 24 hours.
- This is the menstrual cycle (more than one day, a 28-day cycle)
Example: the menstrual cycle, hibernation & SAD. Rhythms with a periodicity of a year are
sometimes referred to as ‘circannual’.
➔ The control of hibernation must involve both external zeitgebers and endogenous
pacemakers that control the infradian rhythm, even in the absence of external
zeitgebers.
➔ In the human physical disorder, Seasonal Affective Disorder (SAD) is a form of
depression that regularly affects vulnerable people in the winter months, so they eat
more and sleep more. In this sense, it is an infradian rhythm of itself.
◆ Research into its treatment has found that for SOME sufferers, brief exposure
to bright light first thing in the morning can be effective against SAD.
◆ One effect of light is to suppress the activity of melatonin (secreted from the
pineal gland), which has a central role in the sleep-waking cycle. This is why
darkness increases melatonin activity, hence the desire to sleep more.
Evaluating infradian rhythms:
Reinberg:
The menstrual cycle is, to some extent, governed by external zeitgebers (external factors).
- Reinberg examined a woman who spent three months in a cave with only a small
lamp to provide light.
- Reinberg stated that her menstrual cycle shortened from the usual 28 days to only
25.
- This result suggests that the lack of light (an external zeitgeber) in the cave
affected her menstrual cycle, and therefore, this demonstrates the effect of external
factors on infradian rhythms
- However, a con of this is that it was only done on one woman, so it is hard to
generalize this information to other women.
Terman:
Evidence supports the role of melatonin in SAD.
- Terman found that the rate of SAD is more common in Northern countries where
the winter nights are longer.
- He found that SAD affects roughly 10% of people living in New Hampshire
- And only 2% of residents in Southern Florida.
- These results suggest that SAD is in part affected by light (external zeitgebers) that
results in increased levels of melatonin
- However, a con of this study is that Terman didn’t take into consideration the living
standards during the winter in these countries, therefore, the limited exposure to
light could not be what caused their SAD.
, Ultradian
= biological rhythms that have a cycle length of less than 24 hours.
Example: the alternation between REM / NREM (Rapid Eye Movement & Non Rapid Eye
Movement) sleep at night (repeats every 90 minutes).
● During a night's sleep, we move systematically through different phases of sleep.
From light non-rapid eye movement sleep to deep NREM sleep, then back up to light
NREM sleep and into a phase of rapid eye movement (REM) sleep.
● The control of this cycle involves the Suprachiasmatic nucleus (SCN) and the pineal
gland as the SCN is a group of neurons in the hypothalamus that controls the Pineal
gland and it’s release of melatonin.
A complete sleep cycle goes through the four stages of NREM sleep before entering REM
(stage 5) and then repeating. Research using EEG has highlighted distinct brain wave
patterns during the different stages of sleep
1. Stages 1 & 2 are ‘light sleep’ stages. During these stages brainwave patterns
become slower and more rhythmic, starting with alpha waves and progressing to
theta waves
2. Stages 3 & 4 are ‘deep sleep’ or slow wave sleep stages, where it is difficult to wake
someone up. This stage is associated with slower delta waves.
3. Finally, stage 5 is REM (or dream) sleep. Here the body is paralyzed (to stop the
person from acting out their dream) and brain activity resembles that of an awake
person.
This cycle is offered more than once every 24 hours. However, another ultradian rhythm is
appetite or meal patterns in humans. Most humans eat three meals a day and appetite rises
and falls because of food consumption.
Tucker et al:
A negative of ultradian rhythms is that there are individual differences when studying sleep
cycles in people hence making it difficult to investigate the patterns.
- Tucker et al found significant differences between participants in terms of the
duration of each stage, particularly stages 3 and 4.
- This demonstrates that there may be innate individual differences in ultradian
rhythms. Meaning that it is worth focusing on these differences during
investigations into sleep cycles.
+ This study was carried out in a controlled lab setting, which meant that the
differences in sleep patterns could not be attributed to situational factors, but only
to biological differences between participants.
Randy Gardener:
This case study suggests the flexibility of ultradian rhythms.
- Randy stayed awake for 264 hours. Experiencing numerous problems like blurred
vision and disorganized speech.
- After the experience, Randy slept for just 15 hours, and over several nights he
recovered only 25% of his lost sleep.
- Interestingly he recovered 70% of stage 4 sleep, 50% of his REM sleep, and very little
of the other stages.
- These results highlight the large degree of flexibility in terms of the different stages
within the sleep cycle and the variable nature of this ultradian rhythm.
- However, a con of this is that he was the only person to have conducted this study
therefore his findings can't be generalized to the rest of the population as sleep cycles
differ from person to person.
Biology of Sleep
Biological rhythms:
Regular patterns of physiological, behavioral, or cognitive activity. They are divided into:
Circadian
= biological rhythms with a cycle length of 24 hours.
Example: body temperatures in humans & the sleep-waking cycle
➔ It makes sense for the body’s physiological processes to be turned into the
sleep-waking cycle so that energy is provided when needed.
➔ The Suprachiasmatic Nucleus (SCN) and the pineal gland in the brain control this
important biorhythm.
◆ The SCN is situated in the hypothalamus and has an inbuilt rhythm.
◆ The SCN is directly linked to the retina in the eye
◆ So, light activity affects the SCN, which regulates the circadian rhythm
Key Study: Siffre (1975)
Procedure:
- He spent 6 months in an underground cave with no access to natural light
- With the absence of this critical zeitgeber, biological rhythms become what is
called free running (a term used to describe biological rhythms in the absence of
external zeitgebers)
- The cave was artificially lit and could be turned on or off depending on whether he
was sleeping or awake, on his command
- He could sleep and eat when he wanted to
- A variety of psychological functions were recorded, including body temperature,
heart rate, blood pressure, and of course his sleep and waking cycle.
Key findings:
- Siffres's waking circadian rhythm extended from the normal 24 hours to between
25-32 hours - meaning his days became longer.
- When it was time for him to leave the cave, he thought he was only on the 151st
day rather than the 179th.
- His body temperature circadian rhythm was more stable. It only extended to 25
hours.
- One outcome of this was that his sleep-wake cycle became
desynchronized from his body temperature rhythm.
- In the absence of environmental zeitgebers such as light, our endogenous
pacemakers or body clocks can still regulate biological rhythms. However, this
regulation is not perfect, so the rhythms are not perfectly turned into the 24-hour
, cycle.
This study suggested that humans use natural light (exogenous zeitgebers) to regulate a
24-hour circadian sleep-wake cycle, demonstrating the importance of light for this
circadian rhythm.
Cons: Pros:
- Methodological issues: This was - Study support: a study on Aschoff
only done once, and only on Siffre. and Wever found that the
Therefore, the information can only sleep-waking cycle of the students
be generalised and taken with was kept in an underground bunker
caution. with similar conditions of Siffre.
- Caused ethical issues: he suffered Although the general picture is
from depression. It can't be done supported, it can't be generalized,
again. and also, these students weren't in
the cave for as long as Siffre was.
Key case study: Stephen and Zucker (1972)
Procedure:
- They investigate the effects of a damaged SCN on circadian rhythms.
- There were two controlled groups of rats in the laboratory
- The first group had a controlled routine where they were given 12 hours of
light followed by another 12 hours of darkness.
- The other group was the group with the broken SCN
- They recorded the amount of water they drank and the level of activity they
performed
Findings:
- They found that the control group had higher levels of activity and water
consumption than the group with the broken SCN. This is because they believe
that damage to the SCN eliminates the normal circadian patterns of drinking and
activity.
- They concluded that the SCN is one of the key pacemakers in the brain controlling
circadian rhythms.
Cons: Pros:
Methodological issues: Controlled study:
- Stephen and Zucker also damaged - Unlike Siffre’s study, this one was a
other parts of the hypothalamus to more scientific and controlled study
show that this did not affect of endogenous pacemakers. And
circadian rhythms. However, the because it was done on a rat, it
surgical method that was used was easier to control and monitor
caused 11 out of the original 25 to than if it were to be done on a
survive. There is still a possibility human.
that the severity of the operation
might have affected the rat's
behavior.
- The study also used rats, which
raises the issue of the lack of
generalizing from rats to humans.
, That is why it can only be
confirmed if the study was done on
humans
Infradian
= biological rhythms with a cycle length of more than 24 hours.
- This is the menstrual cycle (more than one day, a 28-day cycle)
Example: the menstrual cycle, hibernation & SAD. Rhythms with a periodicity of a year are
sometimes referred to as ‘circannual’.
➔ The control of hibernation must involve both external zeitgebers and endogenous
pacemakers that control the infradian rhythm, even in the absence of external
zeitgebers.
➔ In the human physical disorder, Seasonal Affective Disorder (SAD) is a form of
depression that regularly affects vulnerable people in the winter months, so they eat
more and sleep more. In this sense, it is an infradian rhythm of itself.
◆ Research into its treatment has found that for SOME sufferers, brief exposure
to bright light first thing in the morning can be effective against SAD.
◆ One effect of light is to suppress the activity of melatonin (secreted from the
pineal gland), which has a central role in the sleep-waking cycle. This is why
darkness increases melatonin activity, hence the desire to sleep more.
Evaluating infradian rhythms:
Reinberg:
The menstrual cycle is, to some extent, governed by external zeitgebers (external factors).
- Reinberg examined a woman who spent three months in a cave with only a small
lamp to provide light.
- Reinberg stated that her menstrual cycle shortened from the usual 28 days to only
25.
- This result suggests that the lack of light (an external zeitgeber) in the cave
affected her menstrual cycle, and therefore, this demonstrates the effect of external
factors on infradian rhythms
- However, a con of this is that it was only done on one woman, so it is hard to
generalize this information to other women.
Terman:
Evidence supports the role of melatonin in SAD.
- Terman found that the rate of SAD is more common in Northern countries where
the winter nights are longer.
- He found that SAD affects roughly 10% of people living in New Hampshire
- And only 2% of residents in Southern Florida.
- These results suggest that SAD is in part affected by light (external zeitgebers) that
results in increased levels of melatonin
- However, a con of this study is that Terman didn’t take into consideration the living
standards during the winter in these countries, therefore, the limited exposure to
light could not be what caused their SAD.
, Ultradian
= biological rhythms that have a cycle length of less than 24 hours.
Example: the alternation between REM / NREM (Rapid Eye Movement & Non Rapid Eye
Movement) sleep at night (repeats every 90 minutes).
● During a night's sleep, we move systematically through different phases of sleep.
From light non-rapid eye movement sleep to deep NREM sleep, then back up to light
NREM sleep and into a phase of rapid eye movement (REM) sleep.
● The control of this cycle involves the Suprachiasmatic nucleus (SCN) and the pineal
gland as the SCN is a group of neurons in the hypothalamus that controls the Pineal
gland and it’s release of melatonin.
A complete sleep cycle goes through the four stages of NREM sleep before entering REM
(stage 5) and then repeating. Research using EEG has highlighted distinct brain wave
patterns during the different stages of sleep
1. Stages 1 & 2 are ‘light sleep’ stages. During these stages brainwave patterns
become slower and more rhythmic, starting with alpha waves and progressing to
theta waves
2. Stages 3 & 4 are ‘deep sleep’ or slow wave sleep stages, where it is difficult to wake
someone up. This stage is associated with slower delta waves.
3. Finally, stage 5 is REM (or dream) sleep. Here the body is paralyzed (to stop the
person from acting out their dream) and brain activity resembles that of an awake
person.
This cycle is offered more than once every 24 hours. However, another ultradian rhythm is
appetite or meal patterns in humans. Most humans eat three meals a day and appetite rises
and falls because of food consumption.
Tucker et al:
A negative of ultradian rhythms is that there are individual differences when studying sleep
cycles in people hence making it difficult to investigate the patterns.
- Tucker et al found significant differences between participants in terms of the
duration of each stage, particularly stages 3 and 4.
- This demonstrates that there may be innate individual differences in ultradian
rhythms. Meaning that it is worth focusing on these differences during
investigations into sleep cycles.
+ This study was carried out in a controlled lab setting, which meant that the
differences in sleep patterns could not be attributed to situational factors, but only
to biological differences between participants.
Randy Gardener:
This case study suggests the flexibility of ultradian rhythms.
- Randy stayed awake for 264 hours. Experiencing numerous problems like blurred
vision and disorganized speech.
- After the experience, Randy slept for just 15 hours, and over several nights he
recovered only 25% of his lost sleep.
- Interestingly he recovered 70% of stage 4 sleep, 50% of his REM sleep, and very little
of the other stages.
- These results highlight the large degree of flexibility in terms of the different stages
within the sleep cycle and the variable nature of this ultradian rhythm.
- However, a con of this is that he was the only person to have conducted this study
therefore his findings can't be generalized to the rest of the population as sleep cycles
differ from person to person.
