Differences in electroencephalographic non-rapid-eye movement sleep slow-wave characteristics between young and old mice

Abstract

Changes in sleep pattern are typical for the normal aging process. However, aged mice show an increase in the amount of sleep, whereas humans show a decrease when aging. Mice are considered an important model in aging studies, and this divergence warrants further investigation. Recently, insights into the network dynamics of cortical activity during sleep were obtained by investigating characteristics of individual electroencephalogram (EEG) slow waves in young and elderly humans. In this study, we investigated, for the first time, the parameters of EEG slow waves, including their incidence, amplitude, duration and slopes, in young (6 months) and older (18–24 months) C57BL/6J mice during undisturbed 24 h, and after a 6-h sleep deprivation (SD). As expected, older mice slept more but, in contrast to humans, absolute NREM sleep EEG slow-wave activity (SWA, spectral power density between 0.5–4 Hz) was higher in the older mice, as compared to the young controls. Furthermore, slow waves in the older mice were characterized by increased amplitude, steeper slopes and fewer multipeak waves, indicating increased synchronization of cortical neurons in aging, opposite to what was found in humans. Our results suggest that older mice, in contrast to elderly humans, live under a high sleep pressure.

Reassessing the validity of slow-wave dynamics as a proxy for NREM sleep homeostasis

“…δ1 SWs ( Fig. 2G; left) resembled what has been previously described in rodents and humans as a multipeak SW (Panagiotou et al, 2017. Conversely, the profile of δ2 SWs was uniformly sinusoidal (right; Fig.…”

“…Raw EEG signals at 200Hz were imported into Matlab (v. 2018, Mathworks Inc.), in addition to sleep/wake scores. EEG were then filtered for δ spectrum (Chebyshev type-II 0.5-4.5 Hz, bandstop at 0.1 and 10 Hz), similar to others (Freyburger et al, 2017, Panagiotou et al, 2017, Massart et al, 2014. To detect slow-waves, a custom-made Matlab algorithm was employed, based on zero-crossings and wave reconstruction closely following others (Freyburger et al, 2017.…”

“…Time-domain analysis, quantifying other aspects SWs, have yielded new insights into their functional significance (Carrier et al, 2011, Freyburger et al, 2017, Vyazovskiy et al, 2009, Massart et al, 2014. For example, increases and decreases in SW slopes and changes to waveform profiles, are believed to reflect a recalibration of neuronal connections that strengthen during preceding waking (Fattinger et al, 2014, Panagiotou et al, 2017, Vyazovskiy et al, 2011, Tononi and Cirelli, 2006.…”

Chronic high‐caloric diet modifies sleep homeostasis in mice

“…On the day of the surgery, control animals ( n = 11) weighed on average 30.7 g (±0.8), whereas HCD fed animals ( n = 9) weighed 47.6 g (±0.8), showing a 65% increase in body weight compared with controls ( p < 0.0001). Under deep anesthesia (Ketamine 100 mg/kg; Xylazine 10 mg/kg; and Atropine 1 mg/kg), EEG recording screws (placed above the somatosensory cortex and cerebellum) and electromyogram (EMG) electrodes (placed on the neck muscle) (Plastics One, Roanoke, VA, USA) were implanted as described previously (Deboer et al., ; Panagiotou, Vyazovskiy, Meijer, & Deboer, ). The wire branches of all electrodes were set in a plastic pedestal fixed to the skull with dental cement.…”

Do Older Adults Need Sleep? A Review of Neuroimaging, Sleep, and Aging Studies

“…By contrast, chronological age was inversely related to REM duration, N2 duration, and N3 duration (slow wave sleep). Interestingly, in rodent models, older mice show greater slow wave activity than younger mice [8], and some human subjects researchers argue that N3 only declines with aging because EEG amplitude declines (guidelines dictate that slow waves be scored only if amplitude is > 75 mV) [1]. However, in studies of aging humans, quantitative EEG analyses have demonstrated that the incidence, frequency, slope, and density of slow waves are altered in older age [9, 10].…”