More Severe Insomnia Complaints in People with Stronger Long-Range Temporal Correlations in Wake Resting-State EEG

Abstract

The complaints of people suffering from Insomnia Disorder (ID) concern both sleep and daytime functioning. However, little is known about wake brain temporal dynamics in people with ID. We therefore assessed possible alterations in Long-Range Temporal Correlations (LRTC) in the amplitude fluctuations of band-filtered oscillations in electroencephalography (EEG) recordings. We investigated whether LRTC differ between cases with ID and matched controls. Within both groups, we moreover investigated whether individual differences in subjective insomnia complaints are associated with LRTC. Resting-state high-density EEG (256-channel) was recorded in 52 participants with ID and 43 age- and sex-matched controls, during Eyes Open (EO) and Eyes Closed (EC). Detrended fluctuation analysis was applied to the amplitude envelope of band-filtered EEG oscillations (theta, alpha, sigma, beta-1, beta-2) to obtain the Hurst exponents (H), as measures of LRTC. Participants rated their subjective insomnia complaints using the Insomnia Severity Index (ISI). Through general linear models, we evaluated whether H, aggregated across electrodes and frequencies, differed between cases and controls, or showed within-group associations with individual differences in ISI. Additionally, we characterized the spatio-spectral profiles of group differences and associations using non-parametric statistics. H did not differ between cases with ID and controls in any of the frequency bands, neither during EO nor EC. During EO, however, within-group associations between H and ISI indicated that individuals who experienced worse sleep quality had stronger LRTC. Spatio-spectral profiles indicated that the associations held most prominently for the amplitude fluctuations of parietal theta oscillations within the ID group, and of centro-frontal beta-1 oscillations in controls. While people suffering from insomnia experience substantially worse sleep quality than controls, their brain dynamics express similar strength of LRTC. In each group, however, individuals experiencing worse sleep quality tend to have stronger LRTC during eyes open wakefulness, in a spatio-spectral range specific for each group. Taken together, the findings indicate that subjective insomnia complaints involve distinct dynamical processes in people with ID and controls. The findings are in agreement with recent reports on decreasing LRTC with sleep depth, and with the hypothesis that sleep balances brain excitability.

Decline of long-range temporal correlations in the human brain during sustained wakefulness

“…Differences in signal power and signal-to-noise ratio may potentially also help to reconcile some perhaps contradictory findings. In a recent study, larger LRTCs associated with higher insomnia complaints were observed within groups of insomnia patients and control subjects and interpreted as a sign of being closer to criticality 51 . Interestingly, no LRTC differences were observed between control and insomnia patient groups.…”

Insomnia Severity in Adults with Autism Spectrum Disorder is Associated with sensory Hyper-Reactivity and Social Skill Impairment

“…Insufficient activation of the subcortical caudate nucleus of the brain is considered key to hyperarousal (Stoffers et al 2014 ) and has been consistently reported in fMRI studies in ASD (Turner et al 2006 ). A recent post-mortem study in ASD (Adorjan et al 2017 ) suggested involvement of reduced caudate interneuron density in the excitation/inhibition disbalance—also implicated in insomnia (Colombo et al 2016a , b ; Van der Werf et al 2010 ). Next to the involvement of subcortical structures, individual differences in brain connectivity have also been implicated in one’s typical quality of sleep.…”

Long-Range Temporal Correlations of Patients in Minimally Conscious State Modulated by Spinal Cord Stimulation

“…Insomnia has also been found to be related to LRTCs. Individuals who experienced worse sleep quality tended to have stronger LRTCs during wakefulness ( Colombo et al, 2016 ). Furthermore, the LRTCs could be controlled by engaging an intrinsic neuroregulation through a closed-loop neuro-feedback stimulation–the LRTCs were found to be stronger during stimulation ( Zhigalov et al, 2016 ).…”

“…(3) The fluctuation function F ( l ) and window length l were transformed into a logarithmic coordinate, and LSM was used to estimate the linear trend and slope α of the fitted line. α is also commonly referred to as the Hurst scaling exponent H ( Colombo et al, 2016 ) or the DFA exponent ( Krzeminski et al, 2017 ). The DFA exponent of the original EEG was abbreviated as DFAE original .…”

“…The GDFAE describes the robust correlation characteristics of a time series ( Colombo et al, 2016 ). When GDFAE =0.5, the signals are white noise with no autocorrelation.…”