Lesson 12 - Ultradian rhythms

Question 1

What are ultradian rhythms?

Answer 1

These are rhythms that occur more than once within 24 hours, like the stages of sleep

Question 2

Stages of sleep

Answer 2

Stages of sleep alternate between REM (Rapid Eye Movement) and NREM (Non Rapid Eye Movement)

Stages 1-2: These are the light sleep stages. Brain waves are slower and more rhythmic, starting with alpha and progressing to theta waves

Stages 2-4: These are the deep sleep stages and it is more difficult to wake. This is more associated with delta waves, which is slower than alpha and theta waves.

Stage 5: This is REM sleep. The body is paralysed to stop the person acting out their dream, and the brain waves resemble that of an awake person (theta waves).

Repeats every 90 minutes.

Question 3

Dement and Kleitman (1957)

Answer 3

AIM: They wanted to investigate the changes in brain activity throughout sleep

METHOD

• 7 adult males and 2 adult females took part. The study went on for up to 61 nights
• They were asked the report to the lab before bed and they were hooked up to an EEG. It took a recording of them for the whole night
• They were asked to not consume caffeine for the day before their sleep was investigated.
• They were woken up at different stages by the sound of a bell 🔔
• They were woken up up to 6 times
• They were woken up around 5-15 minutes into their REM sleep and were asked to record into a machine whether they had a dream and what they could remember.

FINDINGS

• All participants experienced REM sleep every night
• When woken in REM sleep, there were high incidences of dream recall, but not when woken in other stages
• Brain activity was different in very vivid dreams compared to less clear dreams

Question 4

Strengths of ultradian rhythms

Answer 4

• Dement and Kleitman provides a strong case for ultradian rhythms in the sleep cycle
• Ericsson et al (2006) found evidence for the Basic Rest Activity Cycle (BRAC) proposed by Kleitman. They studied a group of violinists and found that 90 minutes was the maximum amount of time for practice and found this trend across many professions, like athletics. Many took a nap after. This shows that ultradian 90-minute rhythms occur when awake as well, and fatigue occurs towards the end.

Question 5

Weaknesses of ultradian rhythms

Answer 5

Tucker et al (2007) found individual differences in sleep patterns which can be genetic or biological in cause. They measured sleep duration, time taken to fall asleep and the amount of time in each stage over 11 days and nights and found individual differences in all characteristics. We must be cautious about how we generalise findings as some people sleep in different cycles.