Dreaming in different stages of sleep

Question 1

Similarities between NREM and REM dreams

Answer 1

Foulkes, 1962

• Subject has emotion
  
  • 50% REM; 32% NREM
• Others have emotion
  
  • 55% REM; 31% NREM
• Clear visual imagery
  
  • 80% REM; 62% NREM

Nielsen 2000

• Used to think there was a bigger difference between the amount of dreams in REM vs. NREM sleep bc of definitions we used (thought-like dreams didn’t count)

Sols 2000

• Forebrain produces REM and NREM dreams
• 10-30% NREM dreams are indistinguishable from REM dreams
• if REM is interrupted, dreaming can still occur

Question 2

Similarities between daydreams and dreams

Answer 2

Foulkes & Fleisher, 1975

• People awake and relaxed, daydreaming
• Was the dream content involuntary? 20%
• Was the dream a hallucination? (Did they believe it was real?) 19%

Showing it’s possible to have sleep-like dreams while still awake. Cognitive view that acknowledges the similarities between REM and NREM dreams.

Question 3

Sleep onset dream complexity

Answer 3

Foulkes, 1965

• Alpha waves, REM (relaxed) - daydreams with self-participation 62%
• Alpha slow eye movement (drifting in & out of stage 1) - 78%
• Stage 1 sleep - 83%
• Stage 2 sleep - 97%
• individual differences - some more likely than others

Question 4

Length of REM and NREM dreams

Answer 4

Antrobus, 1983

• difference between REM and NREM dreams is length (no. words in recall), not content

Stickgold et al., 2001

• Woken in different sleep stages or cued to recall dream after waking on their own; measure total recall count (no. words)
• Woken
  
  • REM ~75 words
  • NREM ~40 words
• Spontaneous wake
  
  • REM became longer (~100 words) but NREM remained the same
• REM length affects dream length but not NREM length
• REM dream length correlates with NREM dream length

Question 5

Reason for lower total recall count for NREM dreams

Answer 5

Conduit et al., 2004

• we produce the same amount of dreams in NREM as in REM but don’t remember them
• Presented tones in stage 2 or REM sleep
• P has to respond with eye movement while still asleep
• recollection of tone significantly less from stage 2 (65%) than REM (100%)
• Amount of times P’s successfully respond to the tone correlates with dream recall frequency

Question 6

Memory sources of dreams

Answer 6

Cavellero (1993)

• P’s woken, tape record dream recall, playback before going back to sleep
• make associations between dream content and waking life - what’s the source of the dream?
• 3 categories
  
  • strict episode - it happened in real life
  • abstract self-reference - e.g. music they like
  • semantic knowledge - e.g. places they know
• REM dreams, 1/3 have episodic sources
• NREM higher rate
• Sleep onset dreams higher rate again
• REM dreams more original than NREM and sleep onset dreams

Question 7

Thought/hallucination dreams

Answer 7

Fosse, Stickgold & Hobson, 2001

• Deeper sleep –> dreams less likely to be thought-like, more likely to be hallucinations
• NREM dreams are more thought-like than REM dreams, which are more hallucinatory

Question 8

Emphasising the difference between REM and NREM dreams

Answer 8

Nielsen 2000

• hypothesised covert REM processes
• operate at sleep onset and 11mins before and after REM sleep
• can be triggered by noisy environments

Hobson 2000

• Dream recall, especially vivid dreams, more likely in REM
• Controlling for dream length (in words) is invalid because the key difference between REM and NREM dreams is length
  
  • REM dreams are longer in words because you need more words to describe them due to vividness and complexity

Question 9

Model of consciousness

Answer 9

Hobson et al., 2000

• 3 dimensions
  
  • activation
  • input of stimuli (internal or external)
  • mode of procesing
• REM sleep
  
  • high activation
  • internal input
  • high acetylcholine
• NREM
  
  • neutral
• Wake
  
  • high activation
  • external input
  • high norepinepherine and serotonin

Question 10

Dreams in narcolepsy

Answer 10

Fosse, 2000

• High activity and bizarreness but aren’t reflective of it - don’t spot bizarreness
• Suggests dream bizarreness is produced by brain neurochemistry rather than activity - different neurochemistry for REM and NREM sleep

Question 11

Controlling for sleep time for REM and NREM dreams

Answer 11

Takeuchi et al., 2011

• 40mins sleep, 40mins awake, go back to sleep
• Equal chance of going into REM or NREM sleep
• REM dream recall usually is after longer sleep time than NREM, so this method is a more valid comparison
  
  • Dream occurrence related to amount of REM sleep in sleep onset rapid eye movement periods (SOREMPs) and amount of wake in NREM periods
  • REM and NREM dreams had same bizarreness but REM dreams higher clarity, vividness and activity
• Suggests NREM and REM dreams are produced by different mechanisms… BUT REM processes could be spilling over into NREM?