1. Recalling and Forgetting Dreams: Theta and
Alpha
Oscillations during Sleep Predict Subsequent
Dream Recall
BY: Cristina Marzano, Michele Ferrara, Federica
Mauro, Fabio Moroni, Maurizio Gorgoni, Daniela
Tempesta, Carlo Cipolli, and Luigi De Gennaro
PowerPoint By: Nirav Patel

2. BACKGROUND
• Journal of Neuroscience
• May 4, 2011

3. BACKGROUND

4. BACKGROUND
• Beta: 15-30 Hz
• Alpha: 9-14 Hz
• Theta: 4-8 Hz
• Delta: 1-3 Hz

5. BACKGROUND
• Electroencephalography (EEG): Records electrical
activity on the scalp
• Polysomnography (PSG): records eye movements
and other bodily functions during sleep
• brain mechanisms underlying dreaming unknown
• how dreams are encoded is unknown
– Dreams not directly accessible
• Rely on spontaneous or provoked awakenings

6. BACKGROUND
• Speculate episodic memory (memory for
episodes in life)
– Encoded in declarative memory (memories that
can be consciously recalled) during sleep

7. BACKGROUND
• In learning task, successful memory formation
= spike in theta wave (4-8 Hz) oscillation
• Frontal theta oscillations during encoding
predict recall
• Theta waves mediate interactions between
prefrontal cortex and medial temporal lobe in
memory encoding

8. HYPOTHESIS
• 1) A higher frontal theta activity should be
associated with the awakening from REM
sleep followed by successful dream recall
compared to those with recall failure
• 2) A successful recall after awakening from
NREM stage 2 should be associated with a
lower alpha power compared with
awakening with no dream recall

9. METHODS
• 65 university students (35 males, 30 females)
• Criteria
– no other sleep, medical, or psychiatric disorder
(as assessed by a 1 week sleep log and a clinical
interview)
– a habitual sleep time between 12:00 A.M. and
8:00 A.M.
– normal sleep duration and schedule
• 7.5 hours of sleep every night

10. PROCEDURE
• Spend 2 nights in sleep lab
– 1st night is used for adaptation
– 2nd night actual recording of data
• PSG indicates what stage of sleep they’re in
– start sleeping at 12:00AM and are awakened 7.5
hours later
• awakened from NREM stage 2 sleep (n=35)
• awakened from REM sleep (n= 30)
– After 5 minutes without stage shift

11. PROCEDURE
• 20/35 awoken from NREM stage 2 recalled
dreams
• 20/30 awoken from REM sleep recalled
dreams
– NREC = non recallers
– REC = recallers

12. PROCEDURE
• One way ANOVAs on REC and NREC groups for PSG
variables after awoken from REM and stage 2 sleep
– TST: total sleep time
– WASO: Wakefulness after sleep onset
– SEI: Sleep efficiency index

13. RESULTS
• No significant difference in PSG measures of
sleep stage at awakening (REM/stage 2)
and dream recall (success/failure).
– stage of awakening did not affect success or
failure of dream recall

14. RESULTS
• Last 5 minutes of sleep before awakening from
REM sleep is dominated by theta wave (4-8
Hz) oscillations

15. RESULTS
• EEG power values for REC and NREC, through
the course of REM sleep, are similar except in
the range of theta waves (4-8 Hz)

16. RESULTS
• Topographic distribution of EEG power shows
a significant difference only for the theta
power: REC showed higher power values than
NREC subjects

17. RESULTS

18. RESULTS
• EEG power values for REC and NREC, through
the course of NREM stage 2 sleep, are similar
except in the range of alpha waves (9-14 Hz)

19. RESULTS
• Looking across all electrodes number of dreams
recalled after morning awakening was
associated positively with the amount of theta
activity in REM sleep (top) and negatively with
alpha activity in stage 2 (bottom)
– Rho Values: correlation values btw/ # of dreams
recalled and, theta activity (top), and alpha activity
on bottom
• positive rho values indicate the presence of a positive
correlation, and vise versa

20. RESULTS

21. Discussion
• Results provide clear EEG evidence that
stage-specific cortical brain oscillations in the
5 min of sleep before morning awakening are
predictive of a successful dream recall.
• A higher frontal theta activity, after
awakening from REM sleep, as well as a
lower alpha activity of the right temporal
area after awakening from stage 2 NREM
sleep predicts successful dream recall

22. THE END