Enhanced Memory Consolidation Via Automatic Sound Stimulation During Non-REM Sleep.
Introduction
Slow-wave sleep (SWS) slow waves and sleep spindle activity have been shown to be crucial for memory consolidation. Recently, memory consolidation has been causally facilitated in human participants via auditory stimuli phase-locked to SWS slow waves.


Aims
Here, we aimed to develop a new acoustic stimulus protocol to facilitate learning and to validate it using different memory tasks. Most importantly, the stimulation setup was automated to be applicable for ambulatory home use.


Methods
Fifteen healthy participants slept 3 nights in the laboratory. Learning was tested with 4 memory tasks (word pairs, serial finger tapping, picture recognition, and face-name association). Additional questionnaires addressed subjective sleep quality and overnight changes in mood. During the stimulus night, auditory stimuli were adjusted and targeted by an unsupervised algorithm to be phase-locked to the negative peak of slow waves in SWS. During the control night no sounds were presented.


Results
Results showed that the sound stimulation increased both slow wave (p = .002) and sleep spindle activity (p < .001). When overnight improvement of memory performance was compared between stimulus and control nights, we found a significant effect in word pair task but not in other memory tasks. The stimulation did not affect sleep structure or subjective sleep quality.


Conclusions
We showed that the memory effect of the SWS-targeted individually triggered single-sound stimulation is specific to verbal associative memory. Moreover, the ambulatory and automated sound stimulus setup was promising and allows for a broad range of potential follow-up studies in the future.
['Leminen|Miika M|MM|', 'Virkkala|Jussi|J|', 'Saure|Emma|E|', 'Paajanen|Teemu|T|', 'Zee|Phyllis C|PC|', 'Santostasi|Giovanni|G|', 'Hublin|Christer|C|', 'Müller|Kiti|K|', 'Porkka-Heiskanen|Tarja|T|', 'Huotilainen|Minna|M|', 'Paunio|Tiina|T|']
D000161:Acoustic Stimulation D000328:Adult D005260:Female D006801:Humans D007858:Learning D008297:Male D000069077:Memory Consolidation D012890:Sleep D012895:Sleep, REM D013016:Sound D011795:Surveys and Questionnaires
memory slow-wave sleep EEG acoustic stimulation auditory-evoked K-complex.