PSYA3 - Sleep

CIRCADIAN RHYTHMS:

• Once every 24 hours
• SCN = internal body clock
• Increased light = increased melatonin

• Siffre - 61 days in cave. Sleep/wake cycle = 25hrs, but reached 48 hrs at one point
• Folkard et al - 12 RP's in isolation. Clock was secretly changed. Only one person's rhythm adapted. 
• Aschoff and Wever - WWII bunker. RP's had 25 hour cycle. 24 hour cycle when returned to normal. 

Ultradian Rhythms:

• More than once every 24 hours. 
• 5 stages of sleep (NREM, SWS, REM)
• 90 minute cycle, 5- times per night. 

• Friedman and Fisher - BRAC - Eating and drinking cycle. Study of psychiatric patients. 
• Dement and Kleitman - REM studies are restricted. Assumption of dreaming sleep. Dreaming can happen in NREM, and not always in REM. 

Infradian Rhythms:

• Less than once every 24 hours. 
• e.g. Menstrual cycle/male monthly cycle
• MENSTRUAL CYCLE: Pituitary glands release hormones which stimulate overy to ripen egg. Progestorone is released which causes increased blood flow. If no pregnancy, lining of womb is shed. 
• MALE MONTHLY CYCLE: Empson - 21 RP's. study over 49-102 days. Body temp and alertness varied over 20 days. 

• Russell et al - Sweat rubbed onto upper lip of another person. Menstrual cycles synchronised. 
• Dalton - Premenstrual Syndrome (physiological problem, psychological symptoms) associated with crime, suicide, accidents. Can be defence in court. 
• Seasonal Affective Disorder - Depression in winter. Melatonin and Serotonin released when dark. 

Endogenous Pacemakers:

• Hypothalamus received information about light, even when eyes are closed. 
• This synchronises the SCN, and sends signal to pineal gland to increase melatonin at night. 

• Morgan - Mutant hamsters with sleep cycles of 20hrs. SCn transplanted into normal hamsters - They showed mutant rhythms. 
• Folkard - Kate Aldcroft spent 25 days in a cave - sleep cycle was 30hrs. Temperature cycle was 24hrs. Therefore, desynchronsation has occured. 

Exogenous Zeitgebers:

• Entrainment - resetting the SCN with Exogenous Zeitgebers, e.g. light, temp., social cues. 

• DeCoursy et al - Destroyed SCN in chipmunks. They were more active at night, and were more likely to be killed. 
• Campbell and Murphy - Shone bright lights onto back of RP's knees. Circadian rhythms shifted, therefore artificial light does have an effect. 

Shift Work:

• Decreased alertness - 00:00-04:00 = low cortisol levels and low body temp. This is a circadian trough. 
• Sleep Deprivation - caused by distractions, light, noise, daytime sleep shorter than night. 
• Effects on health - Knutson et al - shift work for more thatn 15 years = heart disease risk.

• Solomon - Social disruption caused by shift work. Divorce rates are as high as 60%.
• Gold et al - Rotating shifts are worse - constant changes and disruption cause stress. 
• Bambra et al - Forward-rotating shifts are less damaging. 

Jet Lag:

• Symptoms - Loss of apetite, insomnia, depression, fatigue, nausea, disorientation. 
• Winter et al - SCN =1 day to adapt for every 1 hour of time change. 
• Recht et al - Baseball teams from west and east America.                                                      -East to west = Phase delay (won 44%). West to east = Phase advance (won 37%).

• Other factors - Bad sleep before travelling, travelling is tiring, noise, low-oxygen, noisy passengers
• Boivin et al - 31 men, 4 groups. Sleep cycle inverted for 3 days. When awake, exposed to dim lighting and then either:
• Group 1 - Very bright light. (Advanced 5hrs earlier)
• Group 2 - Bright light. (Advanced 3hrs earlier)
• Group 3 - Normal light. (Advanced 1hr earlier)
• Group 4 - Dim light. (Advanced 1hr later)
• Core body temp. was measured.