Closed-loop auditory stimulation (CLAS) does not improve sleep or declarative memory in chronic insomnia

ObjectiveInvestigate whether auditory closed-loop stimulation (CLAS) applied during sleep could be beneficial for sleep and declarative memory in individuals with chronic insomnia. MethodsWe performed a randomized crossover sham-controlled study on 27 individuals with chronic insomnia to assess changes in sleep and declarative memory between a night with CLAS (i.e., 2-ON-OFF blocks auditory tones locked to slow wave up-states during NREM) and a SHAM night. We conducted assessments of memory (word paired-associate learning task) and sleep (morning questionnaire, polysomnographic recordings) during both nights. ResultsWe found that applying CLAS in a population of individuals with chronic insomnia led to an acute increase in SO amplitude after auditory stimulation. However, we found no beneficial effect of a single night of CLAS on subjective and objective sleep or declarative overnight memory performance. There was an association between the increase in SO density during CLAS with fewer markers of sleep fragmentation (i.e., sleep fragmentation index, arousals), suggesting interindividual differences in response to CLAS in chronic insomnia. ConclusionsCLAS stimulation applied during NREM sleep in individuals with chronic insomnia is feasible but did not show consistent effects on EEG markers of sleep regulation. A subgroup of individuals with insomnia may be more responsive to the impact of CLAS on sleep maintenance.