L11 - Ultradian And Infradian Rhythms

Question 1

What are Ultradian Rhythms?

Answer 1

• Span less than 24 hours
• e.g human sleep stages between REM and NREM every 90 minutes
• Each stage shows a distinct EEG pattern. Deep sleep has slow brainwaves and breathing&heart rate decreases.
• During the fifth stage (REM), EEG looks like an awake person and dreaming occurs
• The 90 min cycle is referred to as the Basic Rest Activity Cycle (BRAC), and is continued when awake.
• During the day, we move from a state of alertness into a state of physiological fatigue.
• The human mind can focus for ~90 mins but towards the end, the body runs out of resources resulting in less concentration, fatigue and hunger

Question 2

Evaluation of Ultradian Rhythms

Answer 2

+ Elite violinist were studied and had practised for 90 minutes each session. Violinists frequently napped to recover with the best violinists napping more. The same pattern was found with athletes, chess players and writers.

• A psychologist suggests individual differences are biologically determined which affect the Ultradian Rhythm. Ppts were studied over 11 days and nights in a lab. The researchers assessed sleep duration, time taken to fall asleep and the amount of time in each sleep stage. There were differences in all.

Question 3

What are Infradian Rhythms?

Answer 3

• Span for longer than 24 hours
• E.g Menstrual cycle which has variations from 23-36 day cycles.
• Hormones regulate the menstrual cycle.
• Ovulation occurs half ways through the cycle when oestrogen is highest.
• After ovulation, progesterone increases for possible implantation

Question 4

Evaluation of Infradian Rhythms

Answer 4

+ Can affect behaviour. Women express a preference for feminised male faces when choosing a long term partner, but show a preference for masculinised faces during ovulation.

• Menstrual cycle is governed by other things too. E.g when several women live together, their menstrual cycles synchronise.
  One study took sweat from one group of women and rubbed onto the upper lip of another group of women and their menstrual cycles became synchronised. Suggesting synchronising is affected by pheromones.

Pheromones - chemical substance produced/released into the env by an animal which affects the behaviour of others of the same species