Biology subjects

Hebron, H.

Publications and source records attributed to Hebron, H..

5 recordsLinked to original sources

bioRxiv2026

Tonic REM sleep EEG components predict better mood, cognition and reduce cortical excitability overnight

Rapid Eye Movement (REM) sleep makes up approximately 20% of sleep in the adult human and is altered in psychiatric and neurodegenerative conditions. REM sleep comprises two substates, during which eye movements do (phasic REM) and do not (tonic REM) occur. Tonic REM makes up 70-90% of REM sleep but its role in regulating brain function, mood and cognition remain underexplored. We investigated how seven nights of insufficient sleep (6 h time in bed), compared to sufficient sleep, alter periodic and aperiodic components of the phasic and tonic REM sleep electroencephalography (EEG), in 542 sleep recordings of 36 young adults. Associations between phasic and tonic REM sleep EEG and mood, cognitive performance, and overnight changes in cortical excitability as indexed by 1/f spectral slopes were assessed. Insufficient sleep predominantly affected tonic REM EEG components, specifically the density of theta, the amplitude, density, and frequency of alpha oscillations and the 1/f slope in the 30 to 45 Hz range. These changes associated with mood and cognitive performances, and with overnight reductions in cortical excitability. These results provide evidence for a role of tonic REM sleep in regulating mood and counteracting cognitive deterioration and excitability changes associated with insufficient sleep.

neuroscience↗

bioRxiv2025

Aperiodic EEG Activity Provides a Linear, Bidirectional, and Spatially Uniform Marker of Subjective and Objective Vigilance in Humans, Both Within and Across States

1Vigilance is increasingly conceived as a continuum, ranging from full alertness to deep sleep. Despite its fundamental role in cognition, behaviour, and health, reliable physiological markers of vigilance remain limited, and clinical assessments often rely on subjective or time-consuming evaluations. Traditionally, vigilance has been estimated through visual inspection of the electroencephalogram (EEG), identifying recognizable oscillatory patterns like rapid, wakefulness-defining alpha waves ([~]10 Hz) and large slow waves ([~]1 Hz) which typify sleep. However, these oscillatory features often appear only intermittently and follow complex, non-linear trajectories across time, space, and frequency, limiting their utility for automated, continuous tracking of vigilance. Recent research has shifted attention to the non-oscillatory, or aperiodic, component of the EEG, which may follow simpler dynamics and offer a more robust index of brain state. Yet most studies often continue to use narrowly defined, discrete vigilance states and transitions in only one direction (e.g., from wakefulness to sleep), without jointly examining oscillatory and aperiodic activity. Here, we address these key gaps by evaluating the capacity of both oscillatory and aperiodic features of EEG power spectra, derived from high-density recordings, to predict vigilance as a continuous variable. Across three independent datasets, we consistently show that although oscillatory features reliably track changes in vigilance, they are unequivocally outperformed by aperiodic activity. Aperiodic features demonstrate a stronger, more linear, and spatially consistent relationship with both objective and subjective indices of vigilance, offering a more robust and scalable physiological marker of this fundamental feature of the brain. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=173 SRC="FIGDIR/small/673229v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@1c66d88org.highwire.dtl.DTLVardef@4126b0org.highwire.dtl.DTLVardef@152f10borg.highwire.dtl.DTLVardef@4f413f_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Lateralised modulation of posterior alpha oscillations by closed loop auditory stimulation during memory retention

Alpha oscillations have been implicated in the maintenance of working memory representations. Notably, when memorised content is spatially lateralised, the power of posterior alpha activity exhibits corresponding lateralisation during the retention interval, consistent with the retinotopic organisation of the visual cortex. Beyond power, alpha frequency has also been linked to memory performance, with faster alpha rhythms associated with enhanced retention. These findings position alpha oscillations as a promising target for neuromodulation. In this study, we demonstrate that although alpha frequency is not typically lateralised in a retinotopic manner during working memory retention, such lateralisation can be externally induced. Using alpha closed-loop auditory stimulation (CLAS), and leveraging the phase-dependent responsiveness of alpha oscillations to sound, we successfully modulated alpha frequency asymmetrically between the visual cortices. The extent of induced frequency lateralisation was associated with the behavioural asymmetry in task performance.

neuroscience↗

bioRxiv2024

Closed-loop auditory stimulation targeting alpha and theta oscillations during REM sleep induces phase-dependent power and frequency changes

BackgroundAlpha and theta oscillations characterize the waking human electroencephalogram (EEG) and can be modulated by closed-loop auditory stimulation (CLAS). These oscillations also occur during rapid eye movement (REM) sleep, but whether they can be modulated by CLAS is not known. ObjectiveInvestigate whether CLAS can modulate alpha and theta oscillations during REM sleep in a targeted phase-dependent manner. MethodsWe recorded high-density EEG during an extended overnight sleep period in 18 healthy young adults. Auditory stimulation was delivered during both phasic and tonic REM sleep in alternating 6 s ON and 6 s OFF windows. During the ON windows, stimuli were phase-locked to four orthogonal phases of ongoing alpha or theta oscillations detected in a frontal electrode (Fz). ResultsDuring ON windows, the four orthogonal phases of ongoing alpha and theta oscillations were targeted with high accuracy. Alpha and theta CLAS induced phase-dependent changes in power and frequency at the target location. Frequency-specific effects were observed for alpha trough (speeding up) and rising (slowing down) and theta trough (speeding up) conditions. These phase-dependent changes of CLAS were observed during both REM sleep substages, even though the amplitude evoked by auditory stimuli which were not phase-locked was very much reduced in phasic compared to tonic REM sleep. ConclusionsThis study provides evidence that faster REM sleep rhythms can be modulated by CLAS in a phase-dependent manner. This offers a new approach to investigate how modulation of REM sleep oscillations affects the contribution of this vigilance state to brain function. Highlights- REM sleep alpha and theta oscillations can be modulated using phase-locked CLAS - Phase-dependent changes in power and frequency are observed in the target area - Phase-dependent modulation occurs in phasic and tonic REM sleep Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=124 SRC="FIGDIR/small/582907v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@771baborg.highwire.dtl.DTLVardef@1b9b13corg.highwire.dtl.DTLVardef@22e85corg.highwire.dtl.DTLVardef@1c50edc_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

Perfect Timing: Effects of Auditory Stimulation on Alpha Oscillations During Wakefulness and the Transition to Sleep are Phase-dependent in Humans

Alpha oscillations play a vital role in managing the brains resources, inhibiting neural activity as a function of their phase and amplitude, and are changed in many brain disorders. Developing minimally invasive tools to modulate alpha activity and identifying the parameters that determine its response to exogenous modulators, is essential for the implementation of focussed interventions. We introduce Alpha Closed-Loop Auditory Stimulation (CLAS) as an EEG-based method to augment and investigate these brain rhythms in humans with specificity and selectivity, using targeted auditory stimulation. Across three independent studies, we demonstrate that CLAS alters alpha power, frequency, and connectivity in a phase, amplitude and topography-dependent manner. Using a single-pulse-CLAS evoked potentials approach we show that the effects of auditory stimuli on alpha oscillations and resulting evoked potentials can be explained within the theoretical framework of oscillator theory and a phase-reset mechanism. Finally, we demonstrate the functional relevance of our approach by showing that CLAS modulates sleep onset dynamics in an alpha phase-dependent manner.

neuroscience↗