biological rhythms: ultradian rhythms

Question 1

what are ultradian rhythms?

Answer 1

a type of biological rhythm with a frequency of more than one cycle in 24 hours

Question 2

describe the cycle of sleep

Answer 2

• 5 distinct stages
• spans approximately 90 minutes
• continues throughout the course of the night
• each stage is characterised by a different level of brain which can be monitored using an EEG

Question 3

describe stages 1 of sleep

Answer 3

• light sleep where a person may easily be woken
• brain waves are high frequency and have short amplitude
• alpha waves

Question 4

describe stage 2 of sleep

Answer 4

• alpha waves contiue
• occasional random changes in pattern called sleep spindles

Question 5

describe stages 3 and 4 of sleep

Answer 5

• known as deep sleep or slow wave sleep (SWS)
• brain waves are delta waves with lower frequency and higher amplitude
• difficult to wake someone at this point

Question 6

describe stage 5 of sleep

Answer 6

• REM sleep
• body is paralysed yet brain activity closely resembles that of the awake brain
• brain produces theta waves
• eyes occasionally move around, thus rapid eye movement
• dreams are most often experienced during REM sleep but may also occur in deep sleep

Question 7

EEGs and sleep

Answer 7

• EEGs are used to measure brainwaves in controlled laboratories
• this enables researchers to describe the changes in neural activity during sleep
• digitalised computer images of brainwaves have replaced paper printouts in the last few years as the technology has become more sophisticated
• participants are usually required to arrive at the lab having missed a night’s sleep so they are able to go to sleep relatively quickly

Question 8

what is the basic rest-activity cycle? (BRAC)

Answer 8

• kleitman (1969) suggested a similar 90-minute rhythm cycle that continues during the day
• characterised by a period of alertness followed by a spell of physiological fatigue
• this recurs during the course of the day

Question 9

evidence for BRAC

Answer 9

• anecdotal evidence supports the existence of BRAC such as the frequent observation that students find it difficult to concentrate for periods longer than 90 minutes at a time
• in a widely-cited study of prodigious violinists, ericsson et al. (1993) found the best performers tended to practice for 3 sessions during the course of the day, each session lasting no more than 90 minutes and there being a break between each to ‘recharge’

Question 10

evaluation: improved understanding of age-related changes in sleep

Answer 10

• sleep scientists have observed that SWS reduces with age
• growth hormone is mostly produced during SWS so this is reduced in older people
• cauter et al. (2000) suggested that the resulting sleep deficit may explain various issues in old age, such as reduced alterness
• to increase SWS, relaxation and medication may be used
• this suggests that knowledge of ultradian rhythms has practical value

Question 11

evaluation: significant variation between people

Answer 11

• tucker et al. (2007) found large differences between participants in terms of the duration of each sleep stage, particularly stages 3 and 4
• tucker et al. suggests that these differences are likely to be biologically determined
• this makes it difficult to describe ‘normal sleep’ in any meaningful way

Question 12

evaluation: the sleep lab

Answer 12

• benefits of conducting studies of sleep in lab settings is that extraneous variables can be controlled
• researcher can exclude temporary variables such as noise or temperature that may affect sleep
• however, lab studies involve being attached to complicated machinery, leading participants to sleep in a way that does not represent their ordinary sleep patterns