Infradian Rhythms

Circadian Rhythms

Ultradian Rhythms

Infradian Rhythms

• Rhythms that have a period greater than 24hrs but less than 1 year, example: Monthly Cycles

• Menstrual Cycle (regulate ovulation: to produce and discharge eggs from an ovary)

Pituitary gland releases hormones FSH (follicle stimulating hormone) & LH (luteinizing hormone) Stimulate a follicle in 1 ovary to ripen egg & release oestrogen.

Once egg is ripened, bursting follicle releases progesterone

Lining of womb/increase blood supply prepare for pregnancy … no pregnancy? Levels of pro. falls lining sheds

21 men. Temp. and mood measured over periods (varying

49-102 days) Found occurring changes of body temp. and biased ratings of morning alertness. Cycle length approx. 20 days (Empson, 1977) – historical validity?

Approx. 28 days

Infradian Rhythms

• Seasonal Affective Disorder (SAD)

Infradian rhythms don’t need to be monthly, it can be once a year rhythm/cycle.

Some people suffer from SAD (depressive condition) They become depressed during winter and recover during summer.

Causes of this depression??

Research shows…

Melatonin (hormone) released by pineal gland when it becomes dark. This hormone may be related to chronic depression.

A02

• Menstrual cycle controlled by the release of hormones under the control of the _ _ _ _ _ _ _ _ _ _ _ _ _ _

• But can be controlled by other factors… Research shows when a no. of women live together & don’t take oral contraceptives, tend to menstruate at same time.

• Russell et al. 1980 – What did he find?

• SAD led to effective therapies. Phototherapy: strong lights to decrease (typo in book) _ _ _ _ _ _ _ _ _

• Studies have found this hormone level is changed by phototherapy.

• Murphy et al. (1993) – phototherapy suppresses it.

Question Time

1. What is Infradian rhythms?

2. Process of the menstrual cycle?

3. What did Empson (1977) find?

4. What does SAD stand for?

5. What hormone is released when it gets dark?

6. What therapy is used effectively to treat SAD?

7. What did Murphy et al (1993) find?

Circadian Rhythms

24hr cycle. Controlled by your biological ‘clock’ which changes every day according to environmental time cues. Also regulates other aspects of daily behaviour like temperature and our sleep-wake cycle.

• Sleep-wake Cycle (What happens when your clock is allowed to be ‘free running’? – free of external cues)

Aschoff & Wever (1976) – ppt. in underground ww2 bunker. No environmental time cues (sunlight) Found most ppt. displayed C. Rhythms between 24-25 hrs.

Alter Environmental cues?

Folkard et al. (1985) – 12 ppt. In ‘temporal isolation unit’ for 3 weeks with any light or time cues. All agreed to sleep when clock said 11.45pm and wake at 7.45am. Clock did run normally but slowly became faster. When indicating 24hrs but actually only 22hrs.

Only 1 ppt. rhythm changed to the 22hr regime, rest went back to normal rhythms – showing strong free running rhythm (not affected by environment cues)

Circadian Rhythms

• Temperature

Core body temp. rises to highest at about 4pm and falls about 1ºC over the next 12hrs to a low point at 4am.

Research studies have found…

Certain cognitive (mind) behaviours vary with this temp. rhythm, example:

Folkhard et al. (1977) – tested memory recall (12/13 yr olds) and found long term recall after a week was best when learned to recall material at 3pm rather than 9am.

A02• Sleep-wake Cycle. In all studies, ppt. are isolated from

variables like daylight but not artificial lighting: dim lighting has no affect? Czeisler et al. (1999) changed ppt. _ _ _ _ _ _ _ _ _ rhythms down to 22hrs and up to 28hrs using dim lighting.

• Individual Differences: 1. Cycle Length: can vary anywhere from 13-65hrs (Czeisler et al. 1999) 2. Cycles onset; individuals appear to be innately different terms of when their C. Rhythms reaches its peak. (everyone got different C. rhythms) E.g. Duffy et al. (2000) – found what?

• Temperature. Changes of body temp. cause improvements in cognitive performance? But there is a causal relationship.

• Giesbrecht et al. (1993): cold water, worse perf.

• Wilkinson et al. (1964): + body temp. some improvements.

• Wright et al. (2002): high temp. = increased physiological arousal = improved perf.

Applications of this research?

Chronotherapeutics

How timing affects drug treatment (taking aspirin)

Best time to study? Morning & early evenings (most alert)

Question Time

1. What is Circadian Rhythms?

2. What did Aschoff & Wever (1976) find?

3. What did Folkard et al. in 1977 find? (Temperature)

4. What variable did actually affect Circadian rhythms?

5. What did Duffy et al. (2000) find?

6. What evidence is there to support a causal relationship between temperature and cognitive performance?

Ultradian Rhythms• Sleep Stages. Within the sleep section of the circadian

cycle, there is another rhythm: Ultradian Rhythms. A cycle of NREM (non-rapid eye movement) and REM sleep over the sleep period.

• NREM sleep (4 stages) 1/2: shallow into deep/slow wave sleep (SWS) (3/4). One way to identify these stages is using electroencephalograph (EEG) machine. Progression through the stages is seen by decreasing freq. and increasing size.

• REM sleep: fast, desynchronized EEG = awake state• Cycle continues throughout night: SWS gets shorter,

REM slightly longer.

• Sleep cycle lasts about 60min in early infancy (why babies cry at night?) and increases to 90min in adolescence…

Rhythms which span less than 1 day

Ultradian Rhythms

• Basic rest-activity Cycle.

90min sleep cycle within a 24hr circadian cycle. So there must be a 90min ‘clock’ ticking during the day as well as at night. = BRAC

• Friedman & Fisher (1967) – observed eating and drinking behaviour in a group of mental patients over periods of 6hrs – finding a clear n cycle in eating & drinking.

AO2

• Sleep Stages. One issue with _ _ _ _ _ _ _ _ studies is the thought that REM sleep is linked to dreaming. People have awoken during REM sleep (paradoxical sleep) often to report dreams but this isn't always the case.

• Basic rest-activity cycle. The ___min cycle is a form of timing to ensure that biological processes in the body happen at the same time.

E.g. Orchestra (Circadian Rhythm) …

… Needs a Conductor (BRAC)

Question Time1. What is Ultradian Rhythms? Cycle of what?

2. How many stages are there? What is happening in each?

3. What is an EEG?

4. REM Sleep is characterised by what?

5. What does BRAC stand for?

6. What did Friedman and Fisher find?

7. What is REM sleep usually linked to?