Infradian And Ultradian Rythms

Question 1

Seasonal affective disorder treatment

Answer 1

• If a lack of sunlight creates depression in some people, phototherapy has been found to be an effective treatment.
• 96 patients randomly assigned with winter SAD to one of three bright-light treatments that are about 10 to 20 times brighter than ordinary indoor lights.
• Patients either got an hour and a half of bright light in the morning, an hour and a half in the evening, or a morning placebo of two deactivated negative-ion generators.
• After three weeks, significantly more people in the morning light treatment group than in the placebo group showed significantly more complete or near-complete remission of their symptoms.
• The response to evening light was also better than placebo, but not at a level of significance.
• Importantly, Eastman’s group found that effective phototherapy fostered full remission of
depression.

Question 2

Ultradian rythms

Answer 2

Take less than 24 hours
E.g. the Sleep Stages cycle

Question 3

Infradian rythms

Answer 3

•Take longer than 24 hours
-E.g. the menstrual cycle

Question 4

Evaluation of infradian and ultradian rythms

Answer 4

– Confounding variables in synchronisation of menstrual cycle studies.
– Argument that there are many factors that may affect change in a women’s menstrual cycle including stress and exercise which act as confounding variables.
– This means that any pattern seen in research is no more than would have been expected to occur by chance.
– In addition, research typically involves small sample sizes.
– •Practical application for SAD
– One of the most effective treatments for SAD is a lightbox that stimulates very strong light in the morning and evening.
– It is thought to reset the melatonin levels in people with SAD.
– This relieved symptoms in up to 60% of sufferers.
– Therefore, research into infradian rhythms may have cost benefits for society.
– •However, much of the research of the effects of pheromones is derived from animal studies.
– For example, that sea urchins release pheromones into the surrounding water so other urchins in the colony will simultaneously eject.
– Therefore, animal research is of limited application to human behaviour and pheromone research.

Question 5

Sleep stages

Answer 5

The sleep cycle follows a ultradian rhythm of 90 minutes where
we move between NREM sleep and REM sleep.

Kleitman (1969) described this movement through the stages as the Basic Rest and Activity Cyle(BRAC). He also suggested that we move through a similar cycle of altertness and fatigue during the day. For example research suggest that we can concentrate for approximately 90 minutes before we begin to lose concentration and begin to feel hungry and fatigued.

– REM sleep, on the other hand, is marked by intense brain activity and is a much more
active period of sleep than non-REM.
This stage is heavily regulated by the brainstem (McCarley et al., 1995), which is the region of the brain that connects the cerebrum with the spinal cord. It consists of the midbrain, medulla oblongata, and the pons.
– REM sleep occurs after the brain passes through stages one, two, three and four, it typically occurs approximately every 90 minutes (McCarley et al., 1995).
– During REM sleep, brain activity increases, voluntary muscles are inhibited, and rapid eye movements and dreams occur.