Neuroscience of Consciousness

Sleep microarchitecture is defined by brief electrophysiological events such as K-complexes(KCs), which are traditionally interpreted as discrete oscillatory phenomena involved in sleep maintenance, sensory gating, and cortical down-states. However, electroencephalography(EEG) also contains aperiodic, broadband activity that reflects non-oscillatory population dynamics and varies systematically across sleep stages. Because KCs are large, low-frequency transient waveforms, they also manifest across a broader frequency range, which creates a bidirectional measurement problem in which discrete events and aperiodic activity are difficult to disentangle. This is because aperiodic dynamics alone can generate fluctuations that resemble KCs, while conversely, the KC waveform itself can inflate the low-frequency end of the spectrum, steepening the fitted exponent even when the underlying aperiodic state is unchanged. These confounds blur what constitutes a real KC and a real aperiodic change in the presence of a KC. A KC-locked change in the aperiodic exponent could therefore reflect a genuine cortical state shift, a measurement artifact from the waveform biasing the spectral fit, or both. Here, we use time-resolved spectral parameterization of overnight sleep EEG to characterize aperiodic dynamics around expert-annotated KCs, with a series of controls designed to separate genuine aperiodic state changes from waveform artifacts. A component of the KC-locked aperiodic change survives these controls, suggesting that KCs are accompanied by a genuine shift toward a higher-exponent, inhibition-dominated cortical state. These findings establish aperiodic activity as a meaningful index of state dynamics during KCs and highlight measurement confounds that any event-locked spectral analysis of large transients must consider.

Communication between the brain and cardiovascular system is increasingly recognized as a fundamental determinant of health, yet the mechanisms coordinating neural and cardiac rhythms remain poorly understood. Sleep provides a unique physiological state for investigating neurovisceral integration because cortical slow oscillations (SOs), thalamocortical sleep spindles, and autonomic activity undergo profound reorganization during non-rapid eye movement (NREM) sleep. We analyzed overnight high-density electroencephalography and electrocardiography recordings from 30 healthy adults and quantified interactions among SOs, sleep spindles, cardiac R-peaks, heart rate variability (HRV), spectral slope, and Lempel-Ziv complexity. To assess integrated brain-heart coordination, we developed a Joint Phase-Amplitude Coupling (JPAC) metric that quantifies the corelation between SO phase-dependent modulation of spindle amplitude and cardiac timing. SO-spindle coupling showed the expected fronto-central distribution but was not significantly related to autonomic or cortical state markers. In contrast, SO-R-peak coupling and JPAC systematically tracked physiological state. Stronger JPAC was associated with higher high-frequency HRV, steeper spectral slopes, and lower neural complexity, indicating enhanced coupling during synchronized, parasympathetically dominated NREM sleep. These findings demonstrate coordinated organization of cortical, thalamocortical, and cardiac rhythms within a common oscillatory framework and identify NREM sleep as a state and potential treatment target of large-scale neurovisceral integration.

When we appreciate visual art, we often take our time: We visit museums or galleries and deliberately engage with artworks and their meaning. Yet, our liking might at least partly be shaped by incidental encoding of the artworks' visual features, a process initially independent from sustained engagement. Here, we show that liking for visual art can be predicted from rapid and automatic responses in the visual brain. We recorded EEG responses while participants viewed 999 artworks from the Vienna Art Picture System (VAPS), which features complex artworks that span different categories and art styles. Artworks were shown with a 300ms stimulus-onset-asynchrony (150ms on, 150 off), and participants responded to occasional target images. Using representational similarity analysis, we predicted the geometry of neural representations from the artworks' similarity in liking (based on ratings from a different group of observers), while simultaneously controlling for similarities in other properties (category, art style, valence, arousal, and familiarity). Crucially, neural responses emerging within the first 150ms were robustly connected to liking, even though the task did not afford any liking judgments. Strikingly, this early neural correlate of liking was also observed in a second experiment, in which we presented the same 999 artworks with a 50ms stimulus-onset-asynchrony. Our results show that even under ultra-fast presentation conditions, automatic neural responses rapidly indicate liking. While fully appreciating an artwork may still need deliberate and prolonged engagement, the perceptual basis of whether we like or dislike an artwork seems to be laid in a split second.

Anticipatory neurophysiological activity before unpredictable emotional events has been reported for decades, but the effects are small, difficult to replicate, and obtained almost exclusively in stripped-down laboratory paradigms. Whether they reflect genuine predictive processes or methodological artifacts remains debated; one rarely tested possibility is that such settings mute it. We examined anticipation in an immersive virtual reality (VR) driving simulation whose collision outcomes were assigned by a quantum random number generator, while EEG, photoplethysmography (PPG), EMG, EOG and inertial (IMU) signals were recorded from a single wireless dry-electrode headset built into the VR display. Sixteen participants passively observed 120 driving sequences ending in a collision or no collision. Length-matched pre- and post-stimulus windows were analysed identically with mass-univariate hierarchical general linear models under permutation cluster correction, plus machine-learning classification across held-out participants. Two post-stimulus clusters differentiated the conditions, the largest peaking at 451.6 ms (d = -1.35), with broadband power modulation robust to baseline modelling, decoded from held-out participants with up to 93.8% accuracy. No time-domain effect or decodable information preceded stimulus onset, but a broadband spectral difference did, surviving preregistered controls for expectation bias (run length), time-on-task build-up and ocular or facial-muscle artifact: directionally consistent in 13 of 15 participants, with pre- and post-stimulus power coupled in all 16. Heart rate differentiated the conditions neither alone nor when added to the classifier. The study was preregistered; the BIDS-format data, analysis code and an open-source EEGLAB plugin are publicly available.

When objects are embedded in a complex lighting environment, the illumination they receive depends on their geometric relationship to the environment. We measured performance in an odd-one-out color constancy task, with objects rendered in complex lighting environments. Observers identified the odd object among four objects, with two rendered under each of two lighting environments, sampled from a wide range of object orientations and camera positions. Constancy was high. The presence of a surrounding context increased accuracy. Gloss provided no measurable benefit. We also tested a condition in which the global color impression provided misleading information about the lighting environment, but this impaired performance only slightly. These findings suggest that human color constancy remains robust even under complex lighting environments, contrary to predictions of many simple models of illuminant discounting.

Attentional selection not only increases behavioural performance and neural information for attended stimuli but, in some instances, induces changes in stimulus appearance. While reported appearance changes have mostly concerned the effects of attending to a particular spatial location, here we report a shift in appearance that occurs when attention is directed to one component of a stimulus rapidly alternating at a single spatial location. Our stimuli included two frames of different colors, which alternated at 3.75Hz or 7.5Hz. Participants reported the perceived dominance of one frame's color in the reference stimulus, by comparison with a target stimulus. We found that when one stimulus frame was more salient than the other, with a greater likelihood of capturing exogenous attention, there was an illusory perception that the frame was physically present for a greater proportion of time. When the frames were matched in salience, a task encouraging participants to endogenously direct their attention to one frame produced a smaller shift in appearance. Our results add to the body of literature demonstrating that attention can change appearance, in this case altering the appearance of attended versus unattended stimuli that are presented at the same spatial location. Furthermore, our results demonstrate that at the 'temporal transparent' alternation rate of 7.5Hz, where rapidly alternating stimuli are perceived as two translucent surfaces, attentional selection of one surface can account for the apparent paradox that feature conjunctions are perceived at stimulus alternation rates higher than predicted by the temporal limits of feature binding for other stimuli.

Study Objectives: Sleep disturbances are common in youth with anxiety disorders, yet most prior work relies on subjective measures and does not capture underlying neural processes. We examined whether alterations in non-rapid eye movement (NREM) sleep oscillations are present in children with anxiety disorders and whether these features relate to internalizing symptoms and emotional functioning. Methods: Children aged 9-13 years with diagnosed anxiety disorders (ANX; n = 17) and typically developing non-psychiatric comparison participants (NC; n = 26) completed overnight polysomnography. Slow oscillations (SO) and slow and fast sleep spindles were characterized using validated automated detection algorithms. Participants also completed a pre-sleep emotional processing task, and parents provided standardized measures of youth mental health. Group differences and dimensional associations between NREM oscillations, internalizing symptoms, and behavioral indices of emotional processing were examined. Results: Sleep architecture did not differ between groups. Slow spindle duration was shorter in the ANX group. Across the full sample, shorter slow spindle duration was associated with greater internalizing symptoms, whereas higher SO density was positively associated with internalizing symptoms. Children in the ANX group exhibited greater facial emotional arousal and more frequent look-away behavior during the emotional processing task. Across participants, greater emotional arousal and look-away behavior were associated with shorter spindle duration during subsequent sleep. Conclusions: Specific features of NREM microarchitecture were associated with individual differences in internalizing symptoms and emotional functioning during early adolescence. These findings highlight the potential relevance of NREM oscillations for understanding developmental links between sleep and youth psychopathology.

Humans coordinate their actions while their bodies and brains synchronize in social interactions, yet how behavioral, physiological, and neural dynamics interact during interpersonal coordination remains largely unknown. We investigated how respiration and individual differences influence behavioral and inter-brain synchrony in a musical synchronization task, which requires precise temporal alignment. Eighty-eight individuals first produced a familiar melody at their most comfortable rate to measure their spontaneous production rate (SPR). They then synchronized the melody with a randomly assigned unfamiliar partner under natural (unpaced), instructed in-phase, and instructed anti-phase breathing conditions, while hyperscanning 64-channel electroencephalography (EEG), respiration, auditory-motor timing, and perceived social connectedness were recorded. Relative to natural respiration, both in-phase and anti-phase breathing increased inter-brain phase-locking and perceived social closeness but reduced behavioral synchrony; the instructed respiratory phase relationship was mirrored in their inter-brain relative phase. Differences in phase of respiratory cycles (inhalation and exhalation) also influenced coordination: Inhalation was associated with stronger inter-brain synchronization but less precise and stable behavioral coordination than was exhalation. Moreover, Individual differences influenced coordination: Partners with the faster SPR consistently preceded the slower partners and exhibited an alpha-band inter-brain phase advance in synchronization, whereas dyads with similar SPR showed greater behavioral synchrony and smaller inter-brain phase difference. Our findings identify respiration as a previously overlooked factor that organizes behavioral and neural synchronization, while individual intrinsic rhythms constrain how interacting partners align in time. Together, these findings reveal a dynamic interplay between the rhythms of the body and brain during human social interactions.

Objectives: Opioids disrupt sleep, but how repeated exposure reorganizes thalamocortical networks is unknown. We asked whether morphine alters sleep architecture, regional oscillations, and phase synchronization, and how exposure history modifies these effects. Methods: From mice, we analyzed cortical electroencephalogram (EEG), central medial thalamic (CMT) local field potentials (LFP), and electromyography (EMG) for 24h after the first and fourth injections of morphine and in abstinence, and quantified vigilance-state occupancy, spectral power, state-power correlations, and the weighted phase-lag index (wPLI), which minimizes volume conduction. Results: Morphine produced hyperlocomotion, wake promotion persisting with repeated exposure, non-rapid eye movement (NREM) sleep suppression, complete rapid eye movement (REM) sleep loss, and rebound sleep. Cortex and thalamus dissociated: in NREM sleep after the first injection, cortical delta and low-gamma power increased, while CMT delta, theta, alpha, and beta power decreased. NREM occupancy coupled more strongly to CMT delta and theta power after both injections, whereas cortical wake correlations in theta, alpha, and beta fell and reversed during abstinence. Overall synchronization was altered only in theta and alpha: corticocortical alpha synchronization decreased acutely, and repeated exposure reduced thalamocortical theta synchronization in wake and NREM sleep. During abstinence, sleep architecture and synchronization largely normalized while spectral and state-power abnormalities persisted alongside mechanical hypersensitivity. Conclusions: We found that morphine does not merely reduce sleep; it reorganizes it: cortex and CMT move in opposite directions, thalamocortical phase synchronization is redistributed, and the resulting spectral and state-power abnormalities outlast the recovery of sleep architecture itself rather than producing tolerance.

Background: Adolescent mental health problems have risen alongside increasing sleep disruption and widespread social media use (SMU). However, the mechanisms linking these factors remain unclear. This study concurrently examined objectively measured sleep and SMU in relation to psychopathology to test whether SMU moderates the sleep-mental health association and to characterize day-to-day bidirectional relations among sleep, affect, mood, and SMU during the school year. Methods: Eighty-five adolescents (ages 12-18) completed 14 days of wrist actigraphy, smartphone-based ecological momentary assessments of mood and affect, and objective SMU duration tracking. Cross-sectional models tested whether SMU moderated associations between sleep and psychopathology, and multilevel daily models examined within-person lagged associations among sleep, SMU, and affect, controlling for age and sex. False discovery rate correction was applied. Results: Shorter average sleep duration and greater variability in sleep duration between weekdays and weekends were associated with higher psychopathology symptoms, primarily externalizing problems. SMU duration neither moderated nor directly predicted psychopathology or sleep. Within-person analyses showed that longer-than-usual sleep predicted more positive and less negative affect and lower next-day SMU, though these associations did not survive correction for multiple comparisons. Conclusions: Sleep disruption showed consistent associations with adolescent psychopathology, whereas the amount of time spent on social media did not. These findings suggest that duration-based measures of SMU may incompletely capture adolescents digital experiences and highlight the need for more granular, context-sensitive indicators of online behavior in understanding youth mental health.

Face recognition ability varies enormously across humans. Individuals with face-blindness (prosopagnosia) struggle to recognize even close family members while super-recognizers can identify strangers with exceptional accuracy. Where do ANNs fall within the human face recognition spectrum? Here, we administered the standardized tests used to characterize human face recognition ability to a diverse set of models, allowing us to contextualize a model's performance within the distribution of human behavior. We found that the majority 55% of models to be classified as face-blind and that even the best face-trained models do not cross the human threshold to be considered a super-recognizer. Interrogating the internal representations of these models showed that models that performed well on standardized face recognition tasks were more identity-selective and viewpoint-invariant. We also found that low-performing models did contain some identity information in independent representational subspaces. Removing viewpoint-dependent subspace improved face recognition abilities in 49 of the 53 models tested. Targeted unit ablations further identified opposing contributions, with viewpoint-dependent units disrupting identity coding and viewpoint-tolerant units supporting it. Together, our results show that most AI models are face-blind with worse face recognition ability than humans, and demonstrate how differences across AI models can be used generate testable hypotheses about the computational basis of human face recognition in humans which can then be probed in future studies.

Dance is increasingly delivered as an intervention for social and affective functioning, but a live dyadic encounter confounds several distinct ingredients - social attention, verbal engagement, coordinated movement, and in-the-moment generation - so its neural effects cannot be assigned to any one of them. We recorded dual-brain mobile EEG from adult human participants of both sexes (16 female, 2 male) and a dance instructor across six five-minute conditions that vary these ingredients independently: solitary rest, direct eye gaze, conversation, teacher-led and participant-led mirroring, and free improvisation, with concurrent head-mounted accelerometry. Referencing each condition to eye gaze - socially engaging but nearly motionless - rather than to solitary rest partitioned the response. The components proved dissociable. Nonverbal social attention alone reorganized the power spectrum, flattening the aperiodic exponent (g = -0.97) and desynchronizing alpha-band oscillations (g = -0.90), while leaving inter-regional connectivity unchanged (amplitude g = +0.15; phase g = +0.11). Verbal engagement added high-frequency amplitude coupling (g = +2.61) without further spectral change. Coordinated movement added a decrease in theta/alpha coupling involving the frontoparietal-control network (g = -0.59), the signature of an externally directed state, alongside a further spectral shift (g = -0.61). Movement-vigor covariates, corticokinematic coherence, and aperiodic-adjusted power indicated that the spectral effects were cortical rather than myogenic. Four weeks of improvisational dance training increased empathic responsiveness to others' distress relative to a movie control (g = 0.82). Coordinated social movement thus acts on the brain componentially, with mutual attention rather than motor load establishing the engaged state.

How do we come to "see" the same thing differently after hearing someone else's perspective? Revising an interpretation could reflect changes in how the brain represents the meaning of what we see, changes in how we visually sample the input, or both. To disentangle these mechanisms, we developed MindLibs, an adaptive fMRI and eye-tracking paradigm in which participants generate interpretations of ambiguous photographs and then view alternative interpretations chosen in real time to vary in semantic content from their own. Exposure to semantically distant alternatives revealed a strong link between reinterpretation as reported behaviorally and representational shifts in association cortex, but no systematic relationship between reinterpretation and changes in gaze. In particular, representational shifts in lateral default-mode network regions (DMN-B) predicted reinterpretation independently of shifts in frontoparietal, attention, and visual networks, and independently of whether gaze changed. In contrast, shifts in visual cortex tracked reinterpretation only when gaze also shifted, and contributed no unique variance beyond DMN-B. These findings identify higher-order conceptual reconfiguration, rather than perceptual resampling, as the primary account of how people revise the meaning of an ambiguous scene.

Primates use eye movements to explore and gather information about their external, visual world. Similarly, even when there is nothing to see spontaneous eye movements reflect the structure and the exploration of internal, conceptual knowledge. However, it remains unclear what mechanism links eye movements to this internal search process. One possibility is that eye movements reflect visual imagery or visual exploration strategies used to explore conceptual knowledge. On the other hand, eye movements may reflect attentional movements in the conceptual space, which are independent from visual experience. Early blind individuals are a useful testbed for this hypothesis in that they never had access to functional vision, thus ruling out the influence of imagery or recycling of visual exploration strategies. To this end, we asked early blind individuals to perform a random number generation task while recording their eye movements. Using electrooculography (EOG), we found that eye movements track the exploration of the mental number line in both sighted and blind: participants moved their eyes to the right for positive changes in magnitude in the number sequence and to the left for negative changes, with eye movement amplitude scaling with the magnitude difference. Furthermore, sighted and early blind participants showed a similar temporal profile, with the effect peaking around 750 ms before number onset. These findings support the hypothesis that internally generated shifts of attention, rather than eye movements per se, drive the exploration of conceptual spaces.

Age is a fundamental social attribute that affects rights, responsibilities and even social status. Color information of the face can affect perceived age, but the nature of its contribution, independent of luminance information, remains underexplored. To better characterize the role of color in age perception, we conducted two experiments. In our first experiment, we tested whether natural age-related changes in facial color alone can drive changes in perceived age. In our second experiment, we manipulated red-green contrast across faces aged 18-91 and tested the effect of this manipulation of perceived youthfulness. Our findings demonstrate that natural age-related color changes do provide cues for age perception, dissociable from luminance information. We also found that the optimal red-green contrast level to make faces look the youngest was significantly higher than the originals, meaning that faces tended to appear younger when their redness was accentuated, even though average face redness increases with age. Our analysis revealed that younger faces required greater increases in redness level compared to their older counterparts to achieve the youngest appearance. These results suggest that the spatial distribution of redness contributes to apparent youthfulness, especially in younger faces.

Sleep disturbances are a significant but underrecognized burden for individuals with Lennox-Gastaut Syndrome (LGS) and their caregivers. We conducted a large LGS caregiver survey to assess sleep quality, duration, specific sleep-related issues, and management strategies. Quantitative analysis revealed a significant association between nocturnal seizures and overall seizure frequency, but general sleep metrics in individuals with LGS (e.g., sleep hours, sleep quality) were not associated with seizure burden. In contrast, caregiver sleep was frequently disrupted - particularly in families who co-slept or reported frequent seizures. Nearly 40% of caregivers experienced nightly sleep disturbances. Respondents reported a range of strategies to manage sleep problems, including medication, environmental adjustments, and behavioral routines. Many also expressed frustrations over the limited effectiveness of strategies and inadequate support for sleep issues. These findings underscore the dual impact of LGS-related sleep disturbances on patients and caregivers, and highlight the need for comprehensive, family-centered approaches to sleep health.

Many studies using mouse models of human brain disorders rely on extended recordings of brain electrical activity through electroencephalogram, or EEG. The features that researchers measure in these recordings, such as seizures and epileptiform activity, are deeply influenced by whether the animal is awake, in non-rapid eye movement (NREM) sleep, or in rapid eye movement (REM) sleep. Because total sleep duration varies naturally across animals, rigorous experimental comparisons require classifying the sleep state of every few seconds of a recording. Manual annotation is highly labor-intensive, often requiring hours per subject. While automated scoring tools accelerate this process, they are typically trained exclusively on healthy cohorts and frequently fail when applied to disease models that exhibit atypical or fragmented sleep architecture. Somnus is an open-source Python package designed to automate rodent sleep staging using EEG, muscle activity (EMG), and optional video-tracking data. It includes a robust base model trained on diverse recordings from six independent laboratories, enabling out-of-the-box classification across various equipment setups without requiring prior manual labeling. A central feature of Somnus is its capacity for rapid adaptation to pathological sleep structure. The software provides a graphical interface that directs researchers to the specific epochs where the base model is least certain. Users can manually correct these targeted epochs in a built-in viewer by comparing the model's classification to the raw EEG signal and video, and then use their corrections to fine-tune the model. This workflow empowers researchers to generate accurate custom scorers for complex disease models or novel treatments with just a few minutes of manual correction, bypassing the need to hand-score entire experimental cohorts or develop their own models from scratch.

How do psychedelic drugs alter human brain function? Answering this question relies on our ability to understand how information is stored, transferred, and transformed across the cortex. Here, we leverage a precise mathematical framework for multivariate information decomposition to construct the first comprehensive picture of these processes across five compounds: LSD, psilocybin, ketamine, DMT and 5-MeO-DMT (N=80). We provide a formal and empirical explanation of major prior results, revealing sets of competing underlying phenomena masked by extant approaches. We extend this analysis to novel higher-order phenomena, and we demonstrate how all of these observations can emerge from a minimal generative model in which neural populations operate with reduced self-coupling. In sum, our results suggest that the psychedelic brain is one in which cortical populations become alike, but not necessarily together. This has important implications for models of how psychedelics reorganize brain dynamics to alter subjective experience and alleviate mental health conditions.

Animals and humans often forgo sleep in response to other physiological needs. Prolonged wakefulness leads to a compensatory homeostatic sleep response involving enhanced amounts of sleep and electroencephalographic delta (0.5-4 Hz) power, yet how the type of preceding wakefulness and brain activity affects this response is poorly understood. Here we compared the pattern of brain activity and the homeostatic sleep response following sustained wakefulness induced by either gentle handling (GH), a widely used form of sleep deprivation in rodents; or optogenetic stimulation of neurons involved in avoidance/defensive responses, basal forebrain (BF) vesicular glutamatergic transporter type 2 (vGluT2) neurons. Local infusion of ionotropic glutamate receptor antagonists partially attenuated the wake-inducing effect of vGluT2-stimulation, but not that of GH, suggesting mediation by other non-glutamatergic BF subtypes. These antagonists also tended to produce more NREM sleep and a shorter NREM latency in the recovery period following vGluT2-stimulation. Both manipulations increased high theta (7-9 Hz) during wakefulness, an effect partially blocked by local infusion of the glutamate antagonist cocktail. Enhanced NREM sleep time and NREM delta power in the recovery period were more pronounced following GH than following vGluT2 stimulation. Whole-brain cFos immunohistochemistry revealed stronger neuronal activity in brain regions involved in stress and avoidance/defensive behaviors with vGluT2 stimulation, compared to GH. Our results demonstrate that activation of a brain system involved in defensive behavior (BF vGluT2) elicits a distinct and diminished homeostatic sleep response compared to GH, potentially an evolutionary sleep adaptation which would maintain vigilance in the face of an ongoing threat.

Homeostatic mechanisms adjust synaptic strengths to regulate neuronal activity across wake-sleep cycles. Although sleep supports memory consolidation, limited research has explored how sleep-induced homeostatic changes influence memory outcomes in humans. The EEG-derived aperiodic slope (1/f) could be a candidate measure of homeostatic memory processes through its reflection of neural excitation-inhibition balance. In this study, 27 participants learned object-word pairs, and completed an immediate recognition test before either a nap or equivalent wakeful period. Resting-state EEG was recorded, both before and after learning and the interval, to derive changes in aperiodic slope values. A delayed recognition test then assessed whether changes in the aperiodic slope (i.e., homeostatic activity) across learning and the interval predicted memory accuracy and N400 amplitude, an index of stimulus expectancy and recognition. Our study found evidence to suggest homeostatic renormalisation, for the nap condition only, indicated by a shift towards inhibition across sleep which was inversely related to the slope change across learning. Although the aperiodic slope change across the nap and wake intervals did not predict delayed memory accuracy, a shift towards inhibition during learning was beneficial for memory accuracy, only in the nap condition. Similarly, a shift towards inhibition across learning, followed by a shift towards excitation in the nap condition, predicted reduced N400 amplitudes. This suggests that homeostatic renormalisation across the nap influenced model updating and stimulus expectancy. This study provides evidence for a link between synaptic homeostatic processes and memory consolidation, emphasising the importance of encoding-related aperiodic activity in this relationship.