Biology subjects

Whitmore, N. W.

Publications and source records attributed to Whitmore, N. W..

4 recordsLinked to original sources

bioRxiv2025

Slow wave stimulation using a smartwatch improves sleep quality

BackgroundSlow-wave sleep is critical for sleep quality, cognitive function, and mood. Slow-wave entrainment (SWE) via rhythmic sensory stimulation can enhance slow-wave activity. However, existing implementations rely on EEG systems, thereby limiting accessibility and scalability. Consumer smartwatches offer an opportunity to deliver SWE in home settings without EEG hardware. ObjectiveThis study evaluated whether smartwatch-delivered sensory stimulation applied during smartwatch-estimated deep sleep elicits acute changes in frontal slow-wave EEG activity during home sleep, and whether individual differences in neural responsiveness to stimulation are associated with next-day behavioral and sleep measures. MethodsIn a randomized crossover design, participants recruited offline from the Boston area slept at home for two nights while wearing a consumer smartwatch for stimulation delivery and a portable EEG headband for neural recording. On a single night, participants received block-wise auditory, vibrotactile, or combined stimulation, guided by an automated on-watch sleep-staging model based on heart rate and motion. On the other night, no stimulation was delivered. Event-related changes in frontal delta (1-4 Hz) power were quantified relative to pre-stimulation baselines. Sleep disruption, subjective sleep quality, mood, and cognitive performance were assessed using questionnaires and a computerized Trail Making Test emailed to participants and completed online. ResultsInitiation of sensory stimulation was associated with significant increases in frontal delta power relative to pre-stimulation baseline and matched non-stimulation blocks.Stimulation blocks exhibited lower disruption rates than non-stimulation blocks, suggesting improved sleep stability during stimulation periods. No significant group-level differences were observed between stimulation and non-stimulation nights on measures of sleep quality, mood, or cognition. However, across participants, larger stimulation-evoked increases in delta power were associated with more favorable next-day subjective sleep and mood ratings and fewer clicks to complete the Trail Making Test. 68/93 participants were stimulated overnight. ConclusionsSmartwatch-based slow-wave entrainment delivered during home sleep can elicit reproducible delta EEG responses without sleep disruption. Individual differences in neural responsiveness to stimulation were associated with next-day behavioral measures, suggesting that wearable-based SWE may represent a scalable and accessible approach for improving sleep health. Trial RegistrationThe experiment was retrospectively registered at ISRCTN (registration number pending)

neuroscience↗

bioRxiv2022

Improving Memory via Automated Targeted Memory Reactivation during Sleep

A widely accepted view in memory research is that previously acquired information can be reactivated during sleep, leading to persistent memory storage. Recently, Targeted Memory Reactivation (TMR) has been developed as a technique whereby specific memories can be reactivated during sleep using a sensory stimulus linked to prior learning. TMR can improve various types of memory, raising the possibility that it may be useful for cognitive enhancement and clinical therapy. A major challenge for the expanded use of TMR is that experimenters must manually control stimulation timing and intensity, which is impractical in most settings. To address this limitation, we developed the SleepStim system for automated TMR in the home environment. SleepStim includes a smartwatch to collect movement and heart-rate data, plus a smartphone to emit auditory cues. A machine-learning model identifies periods of deep non-REM sleep and triggers TMR sounds within these periods. We tested whether this system could replicate the spatial-memory benefit of in-lab TMR. Participants learned the locations of objects on a grid, and then half of the object locations were reactivated during sleep over three nights. In an experiment with 61 participants, the TMR effect was nonsignificant but varied systematically with stimulus intensity; low-intensity but not high-intensity stimuli produced memory benefits. In a second experiment with 24 participants, we limited stimulus intensity and found that TMR reliably improved spatial memory, consistent with effects observed in laboratory studies. We conclude that SleepStim can effectively accomplish automated TMR and that avoiding sleep disruption is critical for TMR benefits.

neuroscience↗

bioRxiv2022

Sleep Disruption Selectively Weakens Reactivated Memories

A widely accepted view in memory research is that recently stored information can be reactivated during sleep, leading to memory strengthening. Two recent studies have shown this effect can be reversed in participants with highly disrupted sleep. To test whether weakening of reactivated memories can result directly from sleep disruption, in this experiment we varied the intensity of memory reactivation cues, such that some produced sleep arousals. Prior to sleep, participants (local community members) learned the locations of 75 objects, each accompanied by a sound naturally related to that object. Location recall was tested before and after sleep, and a subset of the sounds were presented during sleep. Reactivation with arousal weakened memories, unlike the improvement typically found. We conclude that reactivated memories can be selectively weakened during sleep, and that memory reactivation may strengthen or weaken memories depending on additional factors such as concurrent sleep disruption. Statement of RelevanceThe results of this study have implications for both human health and basic psychology. Sleep disorders like apnea are associated with memory problems; our results suggest a possible mechanism where frequent arousal may disrupt the naturally occurring reactivation of memory in sleep. These results also highlight the importance of avoiding brief sleep disruption for good sleep hygiene. Finally, we raise the possibility that reactivation with sleep disruption could be used therapeutically to weaken distressing memories. Our observation that memories can also be either weakened or strengthened by sleep reactivation has implications for understanding the mechanisms of memory consolidation. In particular, we suggest that sleep memory reactivation may be a reconsolidation-like process with memory restabilization required after reactivation. Our findings also suggest avenues for future experiments; such as using sleep disruption to study the time course of memory reactivation.

neuroscience↗

bioRxiv2021

Targeted Memory Reactivation of Face-Name LearningDepends on Ample and Undisturbed Slow-Wave Sleep

Face memory, including the ability to recall the name of a familiar person, is often crucial in social interactions, and like many other memory functions, it may rely on sleep. We investigated whether targeted memory reactivation during sleep could improve associative and perceptual aspects of face memory. Participants studied 80 face-name pairs, and then a subset of spoken names was presented unobtrusively during a daytime nap. This reactivation preferentially improved recall for those face-name pairs, as modulated by two factors related to sleep quality. That is, the memory benefit was positively correlated with the duration of stage N3 sleep (slow-wave sleep) and with the extent to which cues presented during SWS did not produce a sleep disruption indexed by increased alpha-band electroencephalographic activity in the 5 seconds after a cue. Follow-up analyses showed that a memory benefit from presenting spoken names during sleep was evident in participants with high amounts of SWS or with low amounts of sleep disruption. We conclude that sleep reactivation can strengthen memory for specific face-name associations and that the effectiveness of reactivation depends on uninterrupted N3 sleep.

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