Reactivating memories during sleep by odors: odor specificity and associated changes in sleep oscillations.
Memories are reactivated during sleep. Re-exposure to olfactory cues during sleep triggers this reactivation and improves later recall performance. Here, we tested if the effects of odor-induced memory reactivations are odor-specific, that is, requiring the same odor during learning and subsequent sleep. We also tested whether odor-induced memory reactivation affects oscillatory EEG activity during sleep, as a putative mechanism underlying memory processing during sleep. Participants learned a visuospatial memory task under the presence of an odor. During subsequent SWS, the same odor, a different odor, or an odorless vehicle was presented. We found that odor re-exposure during sleep significantly improves memory only when the same odor was presented again, whereas exposure to a new odor or the odorless vehicle had no effect. The memory-enhancing effect of the congruent odor was accompanied by significant increases in frontal delta (1.5-4.5 Hz) and parietal fast spindle (13.0-15.0 Hz) power as well as by an increased negative-to-positive slope of the frontal slow oscillation. Our results indicate that odor-induced memory reactivations are odor specific and trigger changes in slow-wave and spindle power possibly reflecting a bottom-up influence of hippocampal memory replay on cortical slow oscillations as well as thalamo-cortical sleep spindles.
University of Zurich, Switzerland.
Julia S
JS
Rihm
Susanne
S
Diekelmann
Jan
J
Born
Björn
B
Rasch
D000328:Adult; D058256:Brain Waves / Q000502:physiology*; D054022:Cerebrum / Q000502:physiology*; D003700:Delta Rhythm / Q000502:physiology; D004576:Electromyography; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D009812:Odorants; D012890:Sleep / Q000502:physiology*; D012903:Smell / Q000502:physiology*; D055815:Young Adult