Lecture 1

Question 1

Describe reasons why sleep is important

Mignot and Nath

$$

COG

Walker et al 2002 - ML 10am, 10pm –.-% improve

corr between Xand what stage of sleep?

Killenger et a.,2011 balloon analog risk task (subjective perception) - caffiene gum

Ellenbogen et al - interference declarative (I + sleep = >)

MH

Johnson et al (2006) YAs lifetime prevalance of sleep disturbance and Psych disorders > inc rate of maj depress in insomnia - PR =3.8 vs those with no sleep complaints

Jansson-Frojmark & Lindblom (2008)

odds of developing A= _.– D= -.–

PH

Immunity Cohen et al 2009 rhinovirus

Endocrine changes Speigal et al 2004 constant protocol

st Onge 2014 5day of 4 or 9 hr SD and effect on craving cal food

CM

Reimund (1999) - FR

Knutson et al (2007) - FFI

Rechtschaffen et al (1987) - rats 5-33 days (BUT Naidoo et al., 2005)

Answer 1

Adaptive Role

• Mignot (2008) - NREM and REM maintained in strong ecological pressures
• Nath et al - universal

Financial Cost

• $50 million from UK economy/ annum

Cognitive Functioning -

• Sleep enhances non-declarative memory
  
  • Motor Learning (Walker et al 2002)
    
    • improvements only seen after sleep in subjects trained in morning or night
      
      • 10 am (no sig imp after 12hrs of wake)
      • 10 pm 20.5% improvement
      • Correlations between performance imporvment and N2 in last quater o the night
  • Risk Taking
    
    • Man-made disasters
    • Balloon Analog Risk Task
    • (Killenger et al., 2011)
    • Assesses risk-taking behaviour
      
      • exploded more balloons the longer they were awake and became more impulsive
      • Self-reported perception of risk-taking did not follow the BART
      • Caffeine (gum) prevented these increases in risky behaviours
  • Declarative memory
    
    • Ellenbogen et al –
      
      • word recall after interfering word list
      • 12 hours break before testing with or without interfering new word list
      • subjects with interference who slept remembered > pairs than those who did extra manipulation of interference work list uncovers the importance of sleep
      • able to show the importance and performance improvements compared to prolonged wakefulness

Mental health

• Johnson et al (2006)
  
  • Assessment of lifetime prevalence of sleep disturbance and psychiatric disorders in YAs
  • also found greatly increase rate of major depression in those with insomnia
    
    • PR =3.8 vs those with no sleep complaints
• Jansson-Frojmark & Lindblom (2008)
  
  • 1498ppts and 1 year follow up question
    
    • odds of developing insomnia
      
      • A=4.27
      • D = 2.28
  • Effect of I at baseline
    
    • A=2.3
    • D=3.51

Physical Health

• Immune
  
  • Cohen et al ()
    
    • 14 days after rhinovirus
    • 2.94 more likey to get a coldwith those sleeping <7hours
• Endocrine changes
  
  • Spiegal et al () constant protocal 10 hrs 4hrs Leptin dec Ghrelin inc in the morning

Cellular maintaince

• Reimund (1999)
  
  • clears accumulation of NT substances free radicals within the brain
• Knutson et al (2007)
  
  • FFI a rare genetic disorder = SSD cause brain degeneration
• Rechtschaffen et al (1987)
  
  • Rotated a disk when test rats started to fall asleep to keep them awake for 5-33 days o Rats suffered skin lesions, ataxia, motor weakness loss of EEG amplitude and death 3/8 died
  • Could be a result of the stress of the procedure – which are important to control for (Naidoo et al., 2005).
  • See Zurich gentle handling procedure though.

Question 2

What is the sleep cycle? What are the main polysomnographic features that distinguish between the different stages of sleep? (S) (2012) (2014)

Answer 2

• the sleep cycle contains four stages
• N1, N2, N3 and REM
• each cycle is 90-100 mins there are 4-5 cycles per night
• Carskadon and Dement
  
  • in the young adult:
    
    • SWS dominates the NREM portion of the sleep cycle towards the first 3^rd of the night.
    • REM episodes are longest in the last 3rd. brief periods of wake tend to intrude later in the night, near REM sleep transitions, but don’t usually last long enough to be remembered in the morning.
• PSG can be used to distinguish the stages
  
  • N1 =
    
    • reduction in alpha activity (amplitude)
    • increase in theta waves,
    • vertex sharp waves
    • aka drowsy sleep.
    • About 5% of sleep.
  • N2 =
    
    • short bursts of sleep spindles
    • increase in amplitude and decrease in frequency forming events called K complexes.
    • About 45-55% of sleep.
    • Muscular activity occurs but EMG signals will decrease and conscious awareness of external environment
  • N3 –
    
    • characterized by delta wave – slow wave sleep this is the stage where parasomnias occur, so PSD may show muscle artefacts indicative of sleep walking talking night terrors etc.
    • About 25% of sleep.
      
      • The time spent in SWS is proportional to prior sleep deprivation
  • REM sleep =
    
    • increase in beta waves, like waking EEG – muscle atonia but eye display rapid eye movement as the eyes are controlled by brainstem –
    • muscle atonia measured using electrodes near chin.
    • About 25% of sleep.

Question 3

what is the sleep cycle in a normal young adult

Carskadon & Dement

Answer 3

Carskadon and Dement
in the young adult:

SWS dominates the NREM portion of the sleep cycle towards the first 3rd of the night.

REM episodes are longest in the last 3rd. brief periods of wake tend to intrude later in the night, near REM sleep transitions, but don’t usually last long enough to be remembered in the morning.

Question 4

what factors can modify the sleep cycle?

Answer 4

Carskadon & Dement -

Multiple factors modify the sleep cycle, e.g.

1. age – cyclic alternation is about 60 mins in newborns, vs. 90 mins in adults.
   
   • SWS decreases markedly with age – in >60 year olds, may not be present at all.
   • REM proportion as a % of total sleep is maintained well into healthy old age.
   • Declines markedly in the case of organic brain dysfunctions in the elderly – suggests maybe a role in executive functions
2. Extremes in temperature modify REM sleep – mammals have minimal ability to thermoregulate during REM.
   
   • Can’t shiver/sweat much as we’re paralysed.

Question 5

What is rapid eye movement sleep, how can it be identified and how does it differ from other sleep stages?

Answer 5

• characterized by:
  
  • vivid and often bizarre, illogical thought content, which is internally generated.
  • phasic eye-movements and muscle atonia (paralysis).
• It occupies around 15-25% of sleep
• some regional brain areas are as metabolically active as during wakefulness.
• The muscle atonia during REM prevents us from acting out our dreams;
• when this mechanism fails this is exactly what patients with REM-sleep behaviour disorder (RBD) do.
• It differs to other stages of sleep as there is low amplitude mixed Hz (wakelike) EEG
  
  • Beta waves similar to wakefulness – and low chin EMG tone due to muscle atonia – ocular artefacts due to REM
• It occupies the second half of the night
• very similar to awake record but sharper fragmented activity
• Carskadon and Dement
  
  • REM sleep EEG is desynchronised (resembling waking) as opposed to NREM which has a synchronous cortical EEG pattern.
  • Muscles are atonic and dreaming is common. Can be identified through the EEG pattern, or also using other elements of PSG e.g. electrooculography can measure the rapid eye movements, electromyography can measure the muscle atonia.
• With EOG, electrodes pick up activity of the eyes in virtue of the electropotential difference between the cornea and the retina (the cornea is positively charged relative to the retina).

Carskadon and Dement – there is dream recall after approximately 80% of REM arousals. It’s an activated brain in a paralysed body.