Spindles are highly heritable as identified by different spindle detectors

Abstract

Study Objectives Sleep spindles, a defining feature of stage N2 sleep, are maximal at central electrodes and are found in the frequency range of the EEG (sigma 11-16Hz) that is known to be heritable. However, relatively little is known about the heritability of spindles. Two recent studies investigating the heritability of spindles reported moderate heritability, but with conflicting results depending on scalp location and spindle type. The present study aimed to definitively assess the heritability of sleep spindle characteristics. Methods We utilized the polysomnography data of 58 monozygotic and 40 dizygotic same-sex twin pairs to identify heritable characteristics of spindles at C3/C4 in stage N2 sleep including density, duration, peak-to-peak amplitude, and oscillation frequency. We implemented and tested a variety of spindle detection algorithms and used two complementary methods of estimating trait heritability. Results We found robust evidence to support strong heritability of spindles regardless of detector method (h 2>0.8). However not all spindle characteristics were equally heritable, and each spindle detection method produced a different pattern of results. Conclusions The sleep spindle in stage N2 sleep is highly heritable, but the heritability differs for individual spindle characteristics and depends on the spindle detector used for analysis.

Sex and Pubertal Differences in the Maturational Trajectories of Sleep Spindles in the Transition from Childhood to Adolescence: A Population-Based Study

“…were not available at both time points, which precluded topographical analysis of spindle metrics in the cross-sectional and longitudinal trajectories for either the entirety of the 6 to 21 life-course or in the transition from ages 5-12 to ages 12-22. However, spindle activity has been shown to be best quantified at central derivations (Goldschmied et al, 2020), assuring the reliability of our findings. Finally, although we were able to calculate the percent of fast spindles, MSS software did not allow estimating the density, power, or peak frequency of fast and slow spindles separately, thus, future studies are necessary to determine the age-related trajectories of those specific characteristics.…”

“…Additionally, not all subjects had available central derivations with contralateral referencing and spectral analyses for those subjects were conducted using the central derivations with ipsilateral referencing used at the time of the PSG (only 122 in cross-sectional analyses and 167 in longitudinal analyses in the present study). Among the subset of records that had both contralateral and ipsilateral channels, we found excellent concordance in both the cross-sectional (Guadagni et al 2019(Guadagni et al , 2020Goldschmied et al, 2020). In brief, the fast Fourier transform (FFT) was applied to 1-second epochs with the window advancing every 0.2 seconds (5 windows/second).…”

“…Power S in each 1-second epoch was divided by the 30 th percentile of power S in all 1-second epochs within each 30-second epoch (power S ratio). A spindle was identified when the power S ratio was >3 for 5 consecutive epochs provided the ratio decreased to <1.5, or power S decreased to <20% of peak power S (whichever was higher) within 5 seconds (Goldschmied et al, 2020). Presumptive spindles were deleted if they occurred during arousals and if the power S ratio within the presumptive spindle was less than the ratios of alpha and beta powers to their respective reference values (30 th percentile in the 30-second epoch).…”

Signal quality and power spectrum analysis of remote ultra long‐term subcutaneous EEG

“…Nocturnal power spectra showed a peak in the sigma range, as a correlate for sleep spindles seen on visual inspection 28 . It is interesting to note that sigma peaks (and spindles) appear clearer in subjects with a vertical or oblique implantation, which likely captures more midline cerebral activity where sleep spindles often predominate in amplitude.…”

Signal quality and power spectrum analysis of remote ultra long-term subcutaneous EEG

“…Sigma is the frequency correlate of sleep spindles. 28 It is interesting to note that sigma peaks appear clearer in subjects with a vertical or oblique implantation, which likely captures more midline cerebral activity where sleep spindles often predominate in amplitude. Interestingly, a sigma peak is seen in the second (more vertical) implantation of S01 (S01_2), but not in the first, horizontal / temporal implantation.…”