Background: Pre-sleep intentions to react to stimuli during sleep affect sleep processes in spite of reductions in conscious awareness. Here, we compare influences of sounds presented during sleep (with and without intentions to react) with the effect of pre-sleep intentions on sleep (with and without sounds being present during sleep).
Methods: Twenty-six young, healthy participants spent two experimental nights in the sleep laboratory. On one night, they were instructed to react to sounds during sleep ("on call"); on the other night, not ("neutral"). Unknown to the subjects, sounds were presented at a low volume in both nights in one group. No sound was presented in any of the two nights in the other group.
Results: The instruction of being "on call" decreased objective sleep efficiency independently of sounds being present or not. In addition, event-related responses to sounds as well as slow-wave activity were reduced when being "on call".
Conclusions: Pre-sleep intentions to react impair sleep independently of sounds actually being present and influence brain responses to sounds during sleep. Our results highlight the importance of subjective relevance for reducing negative impact of external noise sources such as traffic or church bells.
Keywords: ERP; alarms; instructions; on call; replication; sleep.