Sleep restriction over several days does not affect long-term recall of declarative and procedural memories in adolescents.
OBJECTIVE
There is broad evidence that sleep as opposed to waking facilitates the consolidation of both declarative and procedural memory. The current study addressed the question whether different extents of sleep restriction after learning would impair long-term memory consolidation in adolescents.


METHODS
Eighty-eight healthy adolescents were randomized to five different sleep protocols with 9, 8, 7, 6 or 5 h of time in bed for four consecutive nights under controlled conditions that excluded daytime sleep. Declarative (word-pair task) and procedural memory (mirror tracing task) encoding was assessed prior to the sleep restriction protocol. Recall was assessed after two recovery nights following the sleep protocol and 4 weeks later.


RESULTS
Sleep diaries and actigraphy data demonstrated that the participants closely followed the sleep protocols. There were no differences in demographic parameters or memory encoding at baseline. In contrast to the initial prediction, restriction of nocturnal sleep over four consecutive nights had no significant impact on declarative or procedural memory consolidation. Polysomnographic monitoring after sleep restriction demonstrated a high preservation of the amount of slow wave sleep in the restricted conditions.


CONCLUSIONS
The results suggest that adolescents show a high resilience of memory consolidation to substantial sleep curtailment across four nights that might be promoted by increased sleep intensity under conditions of sleep restriction.
Department of Psychiatry and Psychotherapy, University Medical Center Freiburg, Germany. UVoderholzer@Schoen-Kliniken.de
Ulrich
U
Voderholzer
Hannah
H
Piosczyk
Johannes
J
Holz
Nina
N
Landmann
Bernd
B
Feige
Barbara
B
Loessl
Marta
M
Kopasz
John Peter
JP
Doerr
Dieter
D
Riemann
Christoph
C
Nissen
D056044:Actigraphy; D000293:Adolescent; D003071:Cognition / Q000502:physiology; D004569:Electroencephalography; D006801:Humans; D007858:Learning / Q000502:physiology; D008499:Medical Records; D057567:Memory, Long-Term / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology*; D017286:Polysomnography; D012892:Sleep Deprivation / Q000503:physiopathology*