Biology subjects

Jaramillo, V.

Publications and source records attributed to Jaramillo, V..

14 recordsLinked to original sources

bioRxiv2026

REM Sleep Iota Oscillations Across the Lifespan

Iota oscillations are a newly discovered marker of wakefulness and rapid eye movement (REM) sleep. So far, iota in REM sleep has only been reported in the surface electroencephalography (EEG) of a small sample of young adults and in intracranial recordings of epileptic patients. Here, we investigated the presence of these oscillations in a large dataset (N=937) of high-density sleep EEG recordings from individuals 7 to 70 years old. We found that iota spectral peaks during REM sleep were between 25 and 40 Hz, slightly faster than in wake (25-35 Hz). Iota power was significantly associated with REM sleep architecture, increasing with both REM duration and across progressive sleep cycles. Iota peaks were observed in individuals of all ages, although the prevalence decreased gradually with age, from 88% in children to 44% in older adults. Most iota spectral peak properties (frequency, amplitude, timing, topography) likewise shifted with age. The most striking effect, however, was in bandwidth, such that children had narrow iota peaks, older adults had broad iota peaks, and 20-30 year olds could have either. It remains unclear whether narrowband and broadband iota are functionally equivalent. On shorter time scales (< 1 year), iota properties remained stable across measurements. Analyses of a separate dataset of monozygotic and dizygotic twins revealed high heritability of all iota peak properties except bandwidth. Overall, these results establish iota as a genetically determined trait-like marker of REM sleep with unique age-related changes. Iota oscillations open new avenues to investigate the interaction between sleep, genetics, development, and aging.

neuroscience↗

bioRxiv2026

Hippocampal stimulation timed to memory reactivation shapes human sleep oscillatory dynamics and consolidation

Memory consolidation during sleep depends on the precisely timed coordination of hippocampal reactivation with cortical slow oscillations and spindles. In humans this coupling has been characterised correlationally, while causal investigations have required intracranial stimulation in restricted patient cohorts or used non-invasive approaches targeting cortical regions, often obscuring the underlying sleep rhythms. Here we stimulated the human hippocampus during sleep for the first time, applying temporal interference stimulation to the left hippocampal head either concurrently with or prior to induced memory reactivation. Stimulation concurrent with reactivation reduced associative memory forgetting relative to mistimed stimulation and enhanced fast spindle amplitude, preserving the association between slow oscillation-spindle coupling and memory. This behavioural benefit was mediated by a distributed, left-lateralised set of spindle and coupling features. Non-invasively engaging deep hippocampal circuits during sleep offers both a means to probe human memory and a scalable basis for intervention where consolidation fails.

neuroscience↗

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

A universal dynamic routing architecture governs the flow of human cortical activity

Behaviour requires distributed neural processing to be flexibly integrated and segregated, which in turn demands that information be dynamically routed across the brain. However, whether a unifying principle governs the routing of neural activity remains unknown. Here, we report that the flow of cortical activity is directed through canonical routing modes that are conserved across individuals, robust to variations in age, frequency band, brain state, and even the presence of neurodegeneration. These modes are constructed from the divergence and vorticity of the time-varying unit-phase vector field derived from electroencephalogram (EEG) recordings. We show that the canonical routing modes are flexibly combined to generate distinct, state- and function-dependent flow architectures that remain consistent across individuals. Disruption to the routing mode dynamics mechanistically links structural abnormalities and cognitive impairment in Alzheimers disease. Together, these canonical routing modes provide a unified framework for describing, modelling, and predicting the dynamic integration and segregation of macroscopic brain activity underpinning behaviour.

neuroscience↗

bioRxiv2025

Tracing infant sleep neurophysiology longitudinally from 3 to 6 months: EEG insights into brain development

1.Sleep is critical for brain plasticity during early development, yet the individual maturation of sleep neurophysiology in infancy remains poorly characterized. In particular, slow wave activity (SWA) has emerged as a key marker of both cortical maturation and experience-dependent plasticity. Understanding the regional dynamics of sleep neurophysiology early in life could yield critical insights into neurodevelopmental health. We conducted a longitudinal high-density EEG study in 11 healthy infants (3-6 months) assessing non-rapid eye movement (NREM) sleep. We analyzed the maturation of SWA (0.75-4.25 Hz), theta power (4.5-7.5 Hz), and sigma power (9.75-14.75 Hz) across scalp regions and examined their association with behavioral development. From 3 to 6 months, SWA increased maximally in occipital regions, while theta power exhibited a global increase. Sigma power, initially concentrated centrally, dispersed towards frontal regions. Greater power increases over frontal regions correlated with higher motor (theta) and personal-social skill scores (sigma) at 6 months. These findings establish a framework for typical infant sleep EEG maturation, highlighting frequency-specific and regionally distinct developmental patterns. This study provides the first longitudinal evidence that early changes in sleep EEG topography reflect individual developmental trajectories, supporting its utility as a non-invasive and yet precise biomarker for early identification of atypical neurodevelopment at preverbal ages.

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↗

bioRxiv2025

The Infraslow Fluctuation of Sigma Power During Sleep in Young Individuals with Schizophrenia

A reduction in sleep spindles, a major electrophysiological characteristic of Non-Rapid Eye Movement sleep, has been suggested as a potential biomarker of schizophrenia. While research has primarily focused on the spindle quantity, recent studies have begun to explore their temporal dynamics throughout the night. In healthy individuals, sleep spindles fluctuate on an infraslow [~]50-second timescale, alternating between phases of high and low spindle activity. This fluctuation is referred to as the infraslow fluctuation of sigma power (ISFS), which is modulated by noradrenergic activity from the locus coeruleus and linked to the organization of arousal and memory reactivation processes during sleep. Given the known deficit in sleep spindles, dysregulation of noradrenergic activity, and impairments in sleep maintenance and memory in schizophrenia, this study investigates the ISFS in sleep electroencephalography data from individuals with either Childhood-Onset Schizophrenia (COS; N = 17) or Early-Onset Schizophrenia (EOS; N = 11), aged 9 to 21 years, alongside age- and sex-matched healthy controls (N = 56). The presence and strength of the ISFS were reduced in both COS and EOS groups compared to controls, particularly in central-parietal electrodes. No significant differences in these features of the ISFS were found between the two clinical groups, despite group differences in sleep spindle density and clinical characteristics. These findings suggest that the ISFS is observable but reduced in young patients with schizophrenia and support the notion that the timing of sleep spindles may inform pathomechanistic models of the disorder, as well as future diagnostic approaches and interventions.

neuroscience↗

bioRxiv2024

The Infraslow Fluctuation of Sigma Power During Sleep: Links to Markers of Arousal and Memory Reactivation Across Development

Sleep is both a state of disconnection from the environment and a critical period for restoration. But how does sleep balance responsiveness with the protection of key functions? The infraslow fluctuation of sigma power (ISFS)--the clustering of sleep spindles over 10-100 seconds--is thought to regulate this trade-off in rodents. However, the organization of arousal and memory reactivation markers within the human ISFS and its conservation in younger ages remain unclear. This study characterizes the ISFS from childhood to young adulthood (N = 154; ages 8-26), examining its relationship with functional markers. Results indicate that the ISFS is present across all ages, with frequency, variability, and strength increasing from early to late adolescence. Notably, markers of arousal and memory reactivation are organized within the spindle-rich ISFS peak. The consistent presence and organization of the ISFS suggest it is intrinsic to sleep, with adolescence marking a dynamic window. These insights may guide interventions to promote healthier sleep across development.

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↗

bioRxiv2024

Wake EEG oscillation dynamics reflect both sleep need and brain maturation across childhood and adolescence

1An objective measure of brain maturation is highly insightful for monitoring both typical and atypical development. Slow wave activity, recorded in the sleep electroencephalogram (EEG), reliably indexes age-related changes in sleep pressure as well as deficits related to developmental disorders such as attention-deficit hyperactivity disorder (ADHD). We aimed to determine whether wake EEG measured before and after sleep could index the same developmental changes in sleep pressure, using data collected from 163 participants 3-25 years old. We analyzed ageand sleep-dependent changes in two measures of oscillatory activity, amplitudes and density, as well as two measures of aperiodic activity, offsets and exponents. We then compared these wake measures to sleep slow wave amplitudes and slopes. Finally, we compared wake EEG in children with ADHD (N=58) to neurotypical controls. Of the four wake measures, only oscillation amplitudes consistently exhibited the same changes as sleep slow waves. Wake amplitudes decreased with age, decreased after sleep, and this overnight decrease decreased with age. Furthermore, wake amplitudes were significantly related to both sleep slow wave amplitudes and slopes. Wake oscillation densities decreased overnight in children but increased overnight in adolescents and adults. Aperiodic offsets decreased linearly with age, decreased after sleep, and were significantly related to sleep slow wave amplitudes. Aperiodic exponents also decreased with age, but increased after sleep. No wake measure showed significant effects of ADHD. Overall, our results indicate that wake oscillation amplitudes, and to some extent aperiodic offsets, behave like sleep slow waves across sleep and development. At the same time, overnight changes in oscillation densities independently reflect some yet-unknown shift in neural activity around puberty.

neuroscience↗

bioRxiv2021

An Infant Sleep Electroencephalographic Marker of Thalamocortical Connectivity Predicts Behavioral Outcome in Late Infancy

Infancy represents a critical period during which thalamocortical brain connections develop and mature. Deviations in the maturation of thalamocortical connectivity are linked to neurodevelopmental disorders. There is a lack of early biomarkers to detect and localize neuromaturational deviations, which can be overcome with mapping through high-density electroencephalography (hdEEG) assessed in sleep. Specifically, slow waves and spindles in non-rapid eye movement (NREM) sleep are generated by the thalamocortical system, and their characteristics, slow wave slope and spindle density, are closely related to neuroplasticity and learning. Recent studies further suggest that information processing during sleep underlying sleep-dependent learning is promoted by the temporal coupling of slow waves and spindles, yet slow wave-spindle coupling remains unexplored in infancy. Thus, we evaluated three potential biomarkers: 1) slow wave slope, 2) spindle density, and 3) the temporal coupling of slow waves with spindles. We use hdEEG to first examine the occurrence and spatial distribution of these three EEG features in healthy infants and second to evaluate a predictive relationship with later behavioral outcomes. We report four key findings: First, infants EEG features appear locally: slow wave slope is maximal in occipital and frontal areas, whereas spindle density is most pronounced frontocentrally. Second, slow waves and spindles are temporally coupled in infancy, with maximal coupling strength in the occipital areas of the brain. Third, slow wave slope, spindle density, and slow wave-spindle coupling are not associated with concurrent behavioral status (6 months). Fourth, spindle density in central and frontocentral regions at age 6 months predicts later behavioral outcomes at 12 and 24 months. Neither slow wave slope nor slow wave-spindle coupling predict behavioral development. Our results propose spindle density as an early EEG biomarker for identifying thalamocortical maturation, which can potentially be used for early diagnosis of neurodevelopmental disorders in infants. These findings are complemented by our companion paper that demonstrates the linkage of spindle density to infant nighttime movement, framing the possible role of spindles in sensorimotor microcircuitry development. Together, our studies suggest that early sleep habits, thalamocortical maturation, and behavioral outcome are closely interwoven. A crucial next step will be to evaluate whether early therapeutic interventions may be effective to reverse deviations in identified individuals at risk. HighlightsO_LISlow waves and spindles occur in a temporally coupled manner in infancy C_LIO_LISlow wave slope, spindle density, and slow wave-spindle coupling are not related to concurrent behavioral development C_LIO_LISpindle density at 6 months predicts behavioral status at 12 and 24 months C_LIO_LISlow wave slope and slow wave-spindle coupling are not predictive of behavioral development C_LI

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bioRxiv2021

Bedtime to the brain: How infants sleep habits intertwine with sleep neurophysiology

Adequate sleep is critical for development and facilitates the maturation of the neurophysiological circuitries at the basis of cognitive and behavioral function. Observational research has associated sleep problems in early life with worse later cognitive, psychosocial, and somatic health outcomes. Yet, the extent to which day-to-day sleep habits in early life relate to neurophysiology - acutely and long-term - remains to be explored. Here, we report that sleep habits in 32 healthy 6-month-olds assessed with actimetry are linked to fundamental aspects of their neurophysiology measured with high-density electroencephalography (hdEEG). Our study reveals four key findings: First, daytime sleep habits are linked to EEG slow wave activity (SWA). Second, habits of nighttime movement and awakenings from sleep are connected with spindle density. Third, habitual sleep timing is linked to neurophysiological connectivity quantified as Delta-coherence. And lastly, Delta-coherence at age 6 months predicts nighttime sleep duration at age 12 months. These novel findings widen our understanding that infants sleep habits are closely intertwined with three particular levels of neurophysiology: sleep pressure (determined by SWA), the maturation of the thalamocortical system (spindles), and the maturation of cortical connectivity (coherence). Our companion paper complements this insight in the perspective of later developmental outcomes: early thalamocortical connectivity (spindle density) at age 6 months predicts later behavioural status at 12 and 24 months. The crucial next step is to extend this concept to clinical groups to objectively characterize infants sleep habits "at risk" that foster later neurodevelopmental problems. HighlightsO_LIInfants habitual sleep behavior (actimetry) is linked with their sleep neurophysiology (EEG) C_LIO_LIHabits of daytime sleeping (naps) are related to slow wave activity C_LIO_LIInfants movements and awakenings at nighttime are linked to their sleep spindles C_LIO_LISleep timing (infants bedtimes) is associated with cortical connectivity in the EEG C_LI

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bioRxiv2019

Changes in cross-frequency coupling following closed-loop auditory stimulation in non-rapid eye movement sleep

The activity of different brain networks in non-rapid eye movement (NREM) sleep is regulated locally in an experience-dependent manner, reflecting the extent of the network load during wakefulness. In particular, improved task performance after sleep correlates with the local post-learning power increase of neocortical slow waves and faster oscillations such as sleep spindles and their temporal coupling. Recently, it was demonstrated that by targeting slow waves in a particular region at a particular phase with closed-loop auditory stimulation it is possible to locally manipulate slow-wave activity and interact with training-induced neuroplastic changes. Based on this finding, we tested whether closed-loop auditory stimulation targeting the up-phase of slow-waves over the right sensorimotor area might affect power in delta, theta and sigma bands and coupling between these oscillations within the circumscribed region. We demonstrate that while closed-loop auditory stimulation globally enhances power in delta, theta and sigma bands, changes in cross-frequency coupling of these oscillations were more spatially restricted. In particular, stimulation induced a significant decrease of delta-theta coupling in frontal channels, within the area of the strongest baseline coupling between these frequency bands. In contrast, a significant increase in delta-sigma coupling was observed over the right parietal area, located directly posterior to the target electrode. These findings suggest that closed-loop auditory stimulation locally modulates coupling between delta phase and sigma power in a targeted region, which could be used to manipulate sleep-dependent memory formation within the brain network of interest.

neuroscience↗

bioRxiv2017

Diurnal changes in glutamate/glutamine levels of healthy young adults assessed by proton magnetic resonance spectroscopy

Molecular and electrophysiological studies suggest that sleep ensures efficient functioning of the brain by maintaining synaptic homeostasis. The glutamate receptor -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA receptor) is involved in synaptic plasticity processes and it was shown that its expression changes across the sleep wake cycle. Moreover, animal studies have shown that glutamate levels are reduced during non-rapid eye movement (NREM) sleep and that the rate of the decrease is positively correlated with sleep EEG slow wave activity (SWA). In this study, we aimed to assess if proton magnetic resonance spectroscopy (1H-MRS) is sensitive to diurnal changes of glutamate + glutamine (GLX) in healthy young adults and if potential overnight changes of GLX are correlated to SWA. 1H-MRS spectra of 16 adult subjects were measured in the parietal lobe in the evening and in the subsequent morning using a 3T MRI scanner. The night between the scans was recorded with high-density EEG. Our results revealed a significant overnight reduction in GLX levels, whereas other metabolites did not show any significant change. Moreover, the decrease in GLX was positively correlated with the decrease of SWA in the course of the night. Our study demonstrates that quantification of diurnal changes in GLX is possible by means of 1H-MRS and indicates a relationship between changes in GLX and SWA, a marker that is closely linked to the restorative function of sleep. This relationship might be of particular interest in clinical populations in which sleep is disturbed.

neuroscience↗