Naps reliably estimate nocturnal sleep spindle density in health and schizophrenia

Mylonas, Dimitrios; Tocci, Catherine; Coon, William G.; Baran, Bengi; Kohnke, Erin; Zhu, Lin; Vangel, Mark; Stickgold, Robert; Manoach, Dara S.

doi:10.1111/jsr.12968

Cited by 21 publications

(16 citation statements)

References 14 publications

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“…Spindles were automatically detected at every electrode during non-rapid eye movement sleep (NREM; Stage 2 + SWS) sleep using a modification of a previously validated detector to account for inter-individual differences in the peak frequency of slow and fast spindles (Wamsley et al, 2012; Mylonas et al, 2019). As a first step, slow and fast spindle peaks were identified through inspection of the NREM sleep power spectrum.…”

Section: Methodsmentioning

confidence: 99%

“…Spindles were detected on each channel by applying a thresholding algorithm to the extracted wavelet scale in the range corresponding approximately to 12 -15Hz (center frequency 13.5Hz). A spindle was detected whenever the wavelet signal exceeded a threshold of 9 times the median signal amplitude (as opposed to 4.5 times the mean in the original algorithm) of all artifact-free epochs for a minimum of 400 milliseconds (Mylonas et al, 2019). Our main metric of focus was spindle density (spindles per minute) in NREM sleep (stage 2 and SWS) based on previous work showing correlations between spindle density and declarative memory consolidation (Gais et al, 2002;Cox et al, 2012).…”

Section: Sleep Spindle Detectionmentioning

confidence: 99%

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Sleep spindles preferentially consolidate weakly encoded memories

Denis

Mylonas

Poskanzer

et al. 2020

Preprint

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Sleep has been shown to be critical for memory consolidation, and recent research has demonstrated that this consolidation effect is selective, with certain memories being prioritized for strengthening. Initial strength of a memory appears to be one metric the brain uses to prioritize memory traces for sleep-based consolidation, but the role of consolidation-mediating cortical oscillations, such as sleep spindles and slow oscillations, has not been explored. Here, N=54 participants studied pairs of words to three distinct encoding strengths, with recall being tested immediately following learning and again six hours later.N=36 had a two-hour afternoon nap opportunity following learning, whilst the remaining (n=18) remained awake throughout. Results showed a selective benefit of sleep on memory, with sleep preferentially consolidating weakly encoded items (p=.003). The magnitude of this effect (d=0.90, 95%CI=0.29-1.50) was similar when compared to a previous study examining the benefits of a full night of sleep (d=1.36, 95% CI=0.59-2.12). Within the nap group, consolidation of weakly encoded items was associated with sleep spindle density during slow wave sleep (r=.48, p=.003). This association was present when separately examining spindles coupled (r=.41, p=.013), and uncoupled (r=.44, p=.007) with slow oscillations. Memory was significantly better in individuals who showed an amount of slow oscillation-spindle coupling that was greater than what would be expected by chance (p=.006, d=1.15).These relationships were unique to weakly encoded items, with spindles not correlating with memory for intermediate or strong items. This suggests that sleep spindles facilitate selective memory consolidation, guided in part by memory strength. Significance statementGiven the countless pieces of information we encode each day, how does the brain select which memories to commit to long-term storage? Sleep is known to aid in memory consolidation, but less research has examined which memories are prioritized to receive this benefit. Here, we found that compared to staying awake, sleep was associated with better memory for weakly encoded information. This suggests sleep helps to rescue weak memory traces from being forgotten. Sleep spindles, a hallmark oscillation of nonrapid eye movement sleep, mediates consolidation processes. We extended this to show that spindles selectively facilitated consolidation of weakly encoded memories. This provides new evidence for the selective nature of sleep-based consolidation and elucidates a physiological correlate of this preferential benefit.

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Section: Methodsmentioning

confidence: 99%

Section: Sleep Spindle Detectionmentioning

confidence: 99%

Sleep spindles preferentially consolidate weakly encoded memories

Denis

Mylonas

Poskanzer

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…There is a need for further high-quality experimental studies utilising well-powered, accurate and practical methods involving early course psychosis patients to explore the structure of sleep. For instance, recent research has shown afternoon naps to be correlated with nocturnal spindle density in schizophrenia patients; highlighting an alternative method for assessing the spectral content of sleep (Mylonas et al, 2019).…”

Section: Clinical and Research Implicationsmentioning

confidence: 99%

Sleep disturbances and the At Risk Mental State: A systematic review and meta-analysis

Clarke

Chisholm

Cappuccio

et al. 2021

Schizophrenia Research

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“…Sleep spindles were automatically detected at frontal and central electrodes during NREM sleep using a previously-validated wavelet based detector (35,39,40). As a first step, individualized fast and slow spindle peak frequencies were identified through visual inspection of the NREM sleep power spectrum (using both frontal and central electrode sites, with PSD estimated using the same procedure described above).…”

Section: Sleep Spindlesmentioning

confidence: 99%

Sleep Power Spectral Density and Spindles in PTSD and Their Relationship to Symptom Severity

et al. 2021

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Sleep disturbances are common in post-traumatic stress disorder (PTSD), although which sleep microarchitectural characteristics reliably classify those with and without PTSD remains equivocal. Here, we investigated sleep microarchitectural differences (i.e., spectral power, spindle activity) in trauma-exposed individuals that met (n = 45) or did not meet (n = 52) criteria for PTSD and how these differences relate to post-traumatic and related psychopathological symptoms. Using ecologically-relevant home sleep polysomnography recordings, we show that individuals with PTSD exhibit decreased beta spectral power during NREM sleep and increased fast sleep spindle peak frequencies. Contrary to prior reports, spectral power in the beta frequency range (20.31–29.88 Hz) was associated with reduced PTSD symptoms, reduced depression, anxiety and stress and greater subjective ability to regulate emotions. Increased fast frequency spindle activity was not associated with individual differences in psychopathology. Our findings may suggest an adaptive role for beta power during sleep in individuals exposed to a trauma, potentially conferring resilience. Further, we add to a growing body of evidence that spindle activity may be an important biomarker for studying PTSD pathophysiology.

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Naps reliably estimate nocturnal sleep spindle density in health and schizophrenia

Cited by 21 publications

References 14 publications

Sleep spindles preferentially consolidate weakly encoded memories

Sleep spindles preferentially consolidate weakly encoded memories

Sleep disturbances and the At Risk Mental State: A systematic review and meta-analysis

Sleep Power Spectral Density and Spindles in PTSD and Their Relationship to Symptom Severity

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