Brain Waves Research Articles

Alpha Traveling Waves during Working Memory: Disentangling Bottom-up Gating and Top-down Gain Control.

While previous works established the inhibitory role of alpha oscillations during working memory maintenance, it remains an open question whether such an inhibitory control is a top-down process. Here, we attempted to disentangle this issue by considering the spatio-temporal component of waves in the alpha band, i.e., alpha traveling waves. We reanalyzed two pre-existing and open-access EEG datasets (N = 180, 90 males, 80 females, 10 unknown) where participants performed lateralized, visual delayed match-to-sample working memory tasks. In the first dataset, the distractor load was manipulated (2, 4, or 6), whereas in the second dataset, the memory span varied between 1, 3, and 6 items. We focused on the propagation of alpha waves on the anterior-posterior axis during the retention period. Our results reveal an increase in alpha-band forward waves as the distractor load increased, but also an increase in forward waves and a decrease in backward waves as the memory set size increased. Our results also showed a lateralization effect: alpha forward waves exhibited a more pronounced increase in the hemisphere contralateral to the distractors, whereas the reduction in backward waves was stronger in the hemisphere contralateral to the targets. In short, the forward waves were regulated by distractors, whereas targets inversely modulated backward waves. Such a dissociation of goal-related and goal-irrelevant physiological signals suggests the co-existence of bottom-up and top-down inhibitory processes: alpha forward waves might convey a gating effect driven by distractor load, while backward waves may represent direct top-down gain control of downstream visual areas.Significance Statement When exploring the functional role of alpha band neural oscillations during working memory, mostly amplitude modulations have been considered so far, with relatively limited exploration of spatial-temporal dynamics of this rather global brain oscillatory signature. The present study seeks to address this gap by examining the directionality of alpha wave propagation during working memory retention. Our findings offer novel insights into the well-established inhibitory role of alpha waves, demonstrating that this function is manifested differently according to their propagation directions: forward waves seem to facilitate bottom-up gating, while backward waves might mediate top-down gain control.

Balance of power: The choice between trial and participant numbers to optimise the detection of phase-dependent effects

Abstract The fields of neuroscience and psychology are currently in the midst of a so-called reproducibility crisis, with growing concerns regarding a history of weak effect sizes and low statistical power in much of the research published in these fields over the last few decades. Whilst the traditional approach for addressing this criticism has been to increase participant sample sizes, there are many research contexts in which the number of trials per participant may be of equal importance. The present study aimed to compare the relative importance of participants and trials in the detection of phase-dependent phenomena, which are measured across a range of neuroscientific contexts (e.g., neural oscillations, non-invasive brain stimulation). This was achievable within a simulated environment where one can manipulate the strength of this phase dependency in two types of outcome variables: one with normally distributed residuals (idealistic) and one comparable with motor-evoked potentials (an MEP-like variable). We compared the statistical power across thousands of experiments with the same number of sessions per experiment but with different proportions of participants and number of sessions per participant (30 participants × 1 session, 15 participants × 2 sessions, and 10 participants × 3 sessions), with the trials being pooled across sessions for each participant. These simulations were performed for both outcome variables (idealistic and MEP-like) and four different effect sizes (0.075—“weak,” 0.1—“moderate,” 0.125—“strong,” 0.15—“very strong”), as well as separate control scenarios with no true effect. Across all scenarios with (true) discoverable effects, and for both outcome types, there was a statistical benefit for experiments maximising the number of trials rather than the number of participants (i.e., it was always beneficial to recruit fewer participants but have them complete more trials). These findings emphasise the importance of obtaining sufficient individual-level data rather than simply increasing number of participants.

Interpersonal neural synchronization in frontal-temporal regions as new neurophysiological index of interpretation quality: an fNIRS hyperscanning study

ABSTRACT The evaluation of interpretation quality is fundamental to interpreting development. Previous interpretation evaluation studies focused solely on the interpretation itself, overlooking the interlocutors as recipients of the interpretation. We propose a novel approach by evaluating interpretation through mutual understanding between interlocutors. Using fNIRS hyperscanning, we examined neural activities of 20 interlocutor dyads communicating in Chinese-English context with interpreters. Results showed greater interpersonal neural synchronization (INS) in frontal-temporal regions during communication. Notably, INS in the left middle temporal gyrus (MTG) positively related to communication quality. Interpretation scores positively predicted INS in the left MTG, while mental load negatively predicted INS in the left inferior frontal gyrus, suggesting that INS in speech comprehension areas signifies interpretation quality at a semantic level. Moreover, the positive correlation between interpretation training time and INS in the left dorsolateral prefrontal cortex indicates that INS in mentalizing area reflects interpretation quality at a more advanced level.

Attentional Refreshing in Working Memory and Its Interplay with Long-term Memory: A Behavioral and EEG Study.

Despite the growing interest in the study of attentional refreshing, the functioning of this working memory maintenance mechanism, including its cerebral underpinnings, is still debated. In particular, it remains unclear whether refreshing promotes long-term memory and whether it, in return, depends on long-term memory content to operate. Here, we used direct maintenance instructions and measured brain activity to investigate working memory maintenance with two objectives: (1) test if different behavioral and oscillatory patterns could be observed when participants were instructed to use attentional refreshing versus verbal rehearsal, and (2) observe whether and how refreshing is modulated when maintaining novel (pseudowords) versus familiar (words) memoranda. We conducted an EEG experiment using a modified Brown-Peterson task, in which we manipulated the type of maintenance engaged through explicit instructions (verbal rehearsal vs. refreshing), the type of memoranda (words vs. pseudowords), and the memory load (2 vs. 6). Using scalp EEG, we measured both neural oscillations during working memory maintenance and ERPs during the concurrent parity judgment task. For words, we showed that verbal rehearsal benefited more short-term recall whereas refreshing benefited more delayed recall. In keeping with these behavioral differences between maintenance instructions, frontal-midline theta power increased with memory load only when using verbal rehearsal, whereas occipito-parietal alpha desynchronization was larger with refreshing than verbal rehearsal. When maintaining pseudowords, verbal rehearsal also benefitted short-term recall more than refreshing. However, no long-term memory benefit of refreshing was observed for pseudowords, and oscillatory activity was not different under the two maintenance instructions. Our results provide new evidence supporting the independence between attentional refreshing and verbal rehearsal, and bring new insight into refreshing functioning. We discuss the possible interpretations of these results and the implications for the attentional refreshing literature.

Seeing the piles of the velvet bending under our finger sliding over a tactile stimulator improves the feeling of the fabric.

Using friction modulation to simulate fabrics with a tactile stimulator (i.e. virtual surface) is not sufficient to render fabric touch and even more so for hairy fabrics. We hypothesized that seeing the pile of the velvet darken or lighten depending on changes in the finger movement direction on the virtual surface should improve the velvet fabric rendering. Participants actively rubbed a tactile device or a velvet fabric looking at a screen that showed a synthesized image of a velvet that either remained static (V-static) or darkening/lightening with the direction of touch (V-moving). We showed that in V-moving condition, the touched surface was always perceived rougher, which is a descriptor of a real velvet (Experiment 1). Using electroencephalography and sources localization analyses, we found increased activity in the occipital and inferior parietal lobes (Experiment 2) when seeing dark and shining traces during back-and-forth finger movements over the virtual surface. This suggests that these two posterior cortical regions work together to evaluate visuo-tactile congruence between the seen and the felt (tactile). The visuo-tactile binding, evidenced by neural synchronization (specifically, theta band (5-7 Hz) oscillation) in the left inferior posterior parietal lobule, is consistent with enhanced integration of information and probably contributed to the emergence of a more realistic velvet representation.

Critical analysis of Parkinson’s disease detection using EEG sub-bands and gated recurrent unit

Parkinson’s disease, the second most common neurodegenerative disorder in the world. A progressive disease, which can worsen over time and lead to complications like mild cognitive impairments and dementia. The accurate diagnosis of Parkinson’s Disease (PD) remains a critical challenge in medical engineering. This study explores the potential of brain wave patterns for PD detection in healthy and unhealthy patients. The Power Spectral Density (PSD) and proposed PD detection model based on the Gated Recurrent Unit (GRU) is used to analyze brain activities. It was found that the detection of PD in patients was improved by classifying the RAW EEG in conjunction with the sub-bands using PSD as a feature and GRU as a classifier. The performance matrices including accuracy, precision, recall, and F1-score fall within a range of 90% to 98% for alpha, beta, and gamma sub-bands, while the area under the curve in the case of receiver operating characteristics curve achieved the maximum value of 1.00. To assess the differences between the groups with Parkinson’s disease and the healthy group, a statistical significance test was performed. The power spectral density of the two groups differed statistically significantly, according to the results, indicating that they could be useful as biomarkers for the identification of Parkinson’s disease. The results are compared and validated with the standard performance measures.

Study to examine the effect of Brain Gym on brain waves and concentration in athletes: Paper protocol

Brain function is crucial in achieving peak performance. This can determine a person’s motor control and psychological state, such as motivation, attention, goal setting, memory, self-control, decision-making, and concentration. Spontaneous activity of various physical organs such as the brain, heart, and muscles can be a reference when this behavior occurs. This protocol paper aims to determine whether brain exercises can influence athletes’ brain wave activity and concentration levels. The quasi-experimental method used a pretest-posttest control group design involving 68 futsal athletes. Group 1 will use Brain Gym with instrumental music, Group 2 will use Brain Gym with aromatherapy, and Group 3 will use Brain Gym with both aromatherapy and instrumental music. The research will take place at UNPARI, Lubuklinggau, South Sumatra. The results of this research can serve as a basis for developing mental training methods based on the psychophysiological impact of brain wave activity and athletes’ concentration. This highlights the need for better-designed training programs to optimize performance.

The Effect of the Root Bark of Lycium chinense (Lycii Radicis Cortex) on Experimental Periodontitis and Alveolar Bone Loss in Sprague-Dawley Rats

Lycii Radicis Cortex (LRC), the dried root bark of Lycium chinese Mill., has traditionally been used as a medicinal herb in East Asia to treat fever and hyperhidrosis. In the present study, we investigated the effects of LRC extract on ligation-induced experimental periodontitis and associated alveolar bone loss in rats. Twenty-four hours after ligation placement, LRC was orally administered once daily for 10 days. Firstly, LRC administration inhibited anaerobic bacterial proliferation and inflammatory cell infiltration in gingival tissues. Additionally, LRC exhibited anti-inflammatory effects by reducing the expression of inflammatory mediators, including prostaglandin E2, interleukin-1β, and tumor necrosis factor-α. LRC treatment also downregulated mRNA expression of these inflammatory mediators in lipopolysaccharide-stimulated RAW 264.7 cells by inhibiting the mitogen-activated protein kinases and nuclear factor-κB (NF-κB) signaling pathways. Furthermore, LRC showed an antioxidant effect by decreasing the malondialdehyde level and inducible nitric oxide synthase activity in gingival tissues. Moreover, LRC effectively prevented the connective tissue degradation by inhibiting matrix metalloproteinase-8 expression and the loss of collagen-occupied areas in gingival tissues. LRC also decreased the receptor activator of NF-κB ligand/osteoprotegerin (RANKL/OPG) ratio, as well as the number and occupied areas of osteoclasts on the alveolar bone surface, thereby inhibiting alveolar bone loss. In summary, these findings suggest that LRC is a promising medicinal herb for alleviating periodontitis and related alveolar bone loss through its antimicrobial, anti-inflammatory, and antioxidant properties.

Multimodal neuroimaging of hierarchical cognitive control

Cognitive control enables us to translate our knowledge into actions, allowing us to flexibly adjust our behavior, according to environmental contexts, our internal goals, and future plans. Multimodal neuroimaging and neurostimulation techniques have proven essential for advancing our understanding of how cognitive control emerges from the coordination of distributed neuronal activities in the brain. In this review, we examine the literature on multimodal studies of cognitive control. We explore how these studies provide converging evidence for a novel, multiplexed model of cognitive control, in which neural oscillations support different levels of control processing along a functionally hierarchical organization of distinct frontoparietal networks.

The Mindful Brain at Rest: Neural Oscillations and Aperiodic Activity in Experienced Meditators

Abstract Objectives Previous research has demonstrated that mindfulness meditation is associated with a variety of benefits, including improved mental health. Researchers have suggested these benefits may be underpinned by differences in neural oscillations. However, previous studies measuring neural oscillations have not controlled for non-oscillatory neural activity, the power spectrum of which follows a 1/f distribution (whereby the power of neural activity at each frequency is inversely proportional to that frequency (such that as frequency increases, power decreases)) and contributes to power measurements within oscillation frequencies of interest. We applied recently developed methods to determine if past findings related to neural oscillations in meditation are present even after controlling for non-oscillatory 1/f activity. Method Forty-eight experienced meditators and 44 demographically matched non-meditators provided resting electroencephalography (EEG) recordings. Whole-scalp EEG comparisons (topographical ANOVAs) were used to test for differences between meditators and non-meditators in the distribution or global power of activity for theta, alpha, beta, and gamma oscillations, and for the 1/f components slope and intercept using the extended Better OSCillation detection toolbox. Results Results indicated that meditators showed differences in theta, alpha, and gamma oscillatory power compared to non-meditators (all p < 0.05). Post hoc testing suggested that the oscillatory differences were primarily driven by differences in the distribution of neural activity between meditators and non-meditators, rather than differences in the overall power across all scalp electrodes. Conclusions Our results suggest that experience with meditation is associated with higher oscillatory power and altered distributions of theta, alpha, and gamma oscillations, even after controlling for non-oscillatory 1/f activity. Band-specific differences in oscillatory activity may be a mechanism through which meditation leads to neurophysiological benefits. Preregistration This study was not preregistered.

Binaural beats at 0.25 Hz shorten the latency to slow-wave sleep during daytime naps

Binaural beats can entrain neural oscillations and modulate behavioral states. However, the effect of binaural beats, particularly those with slow frequencies (< 1 Hz), on sleep remains poorly understood. We hypothesized that 0.25-Hz beats can entrain neural oscillations and enhance slow-wave sleep by shortening its latency or increasing its duration. To investigate this, we included 12 healthy participants (six women; mean age, 25.4 ± 2.6 years) who underwent four 90-min afternoon nap sessions, comprising a sham condition (without acoustic stimulation) and three binaural-beat conditions (0, 0.25, or 1 Hz) with a 250-Hz carrier tone. The acoustic stimuli, delivered through earphones, were sustained throughout the 90-min nap period. Both N2- and N3- latencies were shorter in the 0.25-Hz binaural beats condition than in the sham condition. We observed no significant results regarding neural entrainment at slow frequencies, such as 0.25 and 1 Hz, and the modulation of sleep oscillations, including delta and sigma activity, by binaural beats. In conclusion, this study demonstrated the potential of binaural beats at slow frequencies, specifically 0.25 Hz, for inducing slow-wave sleep in generally healthy populations.

Machine-Learning-Based Depression Detection Model from Electroencephalograph (EEG) Data Obtained by Consumer-Grade EEG Device

Background/Objectives: There have been attempts to detect depression using medical-grade electroencephalograph (EEG) data based on a machine learning approach. EEG has garnered interest as a method for assessing brainwaves by attaching electrodes to the scalp to obtain electrical activity in the brain. Recently, machine learning has been applied to the EEG data to detect depression, with encouraging results. Specifically, studies using medical-grade EEG data have shown that depression can be accurately detected. However, there is a need to expand the range of applications by achieving a score with machine learning using simpler consumer-grade brain wave sensors. At present, a sufficient score has not been achieved.; Methods: To improve the score of depression detection, we quantified various EEG indices to train models such as power spectrum, asymmetry, complexity, and functional connectivity. In addition, feature selection was performed to ensure that the model learns only promising EEG indices for depression detection. The feature selection methods were Light Gradient Boosting Machine (LightGBM) feature importance, mutual information, ReliefF and ElasticNet coefficients. The selected EEG indices were learned by the LightGBM model, which is reported to be as accurate as the latest deep learning models. In cross-validation, the independence of test and training data was ensured to avoid excessively calculated score; Results: The results showed that the Macro F1 score was 91.59%, suggesting that a consumer-grade EEG can detect depression. In addition, analysis of the EEG indices selected by feature selection indicated that the Macro F1 score was about 80% for single EEG indices such as differential entropy in the frequency band β and functional connectivity in the left frontal region in the frequency band 1–128 Hz; Conclusions: Although the data were obtained from a consumer-grade EEG, the results suggest that these EEG indices are promising for detection depression.

Differential modulations of theta and beta oscillations by audiovisual congruency in letter-speech sound integration.

The integration of visual letters and speech sounds is a crucial part of learning to read. Previous studies investigating this integration have revealed a modulation by audiovisual (AV) congruency, commonly known as the congruency effect. To investigate the cortical oscillations of the congruency effects across different oscillatory frequency bands, we conducted a Japanese priming task in which a visual letter was followed by a speech sound. We analyzed the power and phase properties of oscillatory activities in the theta and beta bands between congruent and incongruent letter-speech sound (L-SS) pairs. Our results revealed stronger theta-band (5-7Hz) power in the congruent condition and cross-modal phase resetting within the auditory cortex, accompanied by enhanced inter-trial phase coherence (ITPC) in the auditory-related areas in response to the congruent condition. The observed congruency effect of theta-band power may reflect increased neural activities in the left auditory region during L-SS integration. Additionally, theta ITPC findings suggest that visual letters amplify neuronal responses to the following corresponding auditory stimulus, which may reflect the differential cross-modal influences in the primary auditory cortex. In contrast, decreased beta-band (20-35 Hz) oscillatory power was observed in the right centroparietal regions for the congruent condition. The reduced beta power seems to be unrelated to the processing of AV integration, but may be interpreted as the brain response to predicting auditory sounds during language processing. Our data provide valuable insights by indicating that oscillations in different frequency bands contribute to the disparate aspects of L-SS integration.

Neural Synchrony of Minds and Machines: Hippocampal Mechanisms to Advance AI and Virtual Networks

Abstract Artificial intelligence (AI) predicts behavior by learning from user data collected through digitally mediated interfaces. Virtual spaces---such as online social networks---extend the physical world into virtual worlds, leveraging AI technologies to transform user behavior into digital assets by mimicking the brain’s reinforcement networks. Social media platforms utilize AI to manipulate user behavior through rewards that can diverge from the user’s intended goals. This misalignment fragments user behavior and cognition, resulting in virtual disembodiment. Presented is a conceptual mechanism based on the hippocampus to synchronize AI and the brain, synthesizing the user’s physical and mental presence in virtual spaces.

Research to reduce pain and increase comfort using skin cleaning materials

During her nursing career, Professor Emeritus Hiroko Shimizu focused on the need for nursing care to promote and support patient recovery and found that the use of steam cloths helped relax patients and reduce their physical and mental pain. Shimizu is affiliated with Kagawa University and has been working to investigate the impact of skin cleaning materials on the brain waves of patients. Shimizu and her collaborators set out to create something that could warm people affected by disasters and relieve the pain of cancer patients. The researchers were the first to employ a method invented by Professor Ichirou Ishimaru to measure moisture using near-infrared two-dimensional Fourier spectrometry. They measured moisture smearing on the skin and found a softening and smoothing effect on the skin. This led them to develop a steam-generating cleaning tool that induces relaxation without a towel or cloth. Part of Shimizu’s work concentrates on developing new techniques and measurement methods needed to verify her findings. The researchers also used text analysis of the subjects’ statements and psychological images to project their thoughts and attitudes towards the care provided, as well as an electroencephalogram analysis by a neurologist, Visiting Professor Tetsuo Toge, to correlate the results. Shimizu plans to incorporate an analysis of steam volume and moisture or images with temperature and humidity into her considerations. In one study, Professor Hidekuni Takao, who shared Professor Shimizu's research, is working as the representative of a Japan Science and Technology Agency (JST)-CREST project to develop a rare device to measure the shape of the skin surface. The goal is that the integrated semiconductor tactile sensor the researchers are developing will have equal or even greater sensitivity and performance than that of a human fingerprint.

Inter-brain synchrony is associated with greater shared identity within naturalistic conversational pairs.

Inter-brain synchrony occurs between individuals who feel connected socially, but how synchrony relates to felt connectedness under naturalistic social interaction has remained enigmatic. We hypothesized that inter-brain synchrony between naturally interacting individuals might be associated with the internalization of a social identity, a link between an individual's personal identity and the social group to which the individual belongs. A convenience sample of sixty participants were split into dyads and interacted naturalistically on a social task. Through mapping EEG oscillatory waveforms onto a conceptual model categorizing the formation of a social identity within a naturalistic conversation, greater inter-brain synchrony was observed in the emergent stage within the formation of a social identity compared to earlier stages, where a social identity was not present. We provide evidence for greater neural synchrony related to higher socio-psychological connectedness during the development of social identity under naturalistic social interaction.

Impact of age-related hearing loss on decompensation of left DLPFC during speech perception in noise: a combined EEG-fNIRS study.

Understanding speech-in-noise is a significant challenge for individuals with age-related hearing loss (ARHL). Evidence suggests that increased activity in the frontal cortex compensates for impaired speech perception in healthy aging older adults. However, whether older adults with ARHL still show preserved compensatory function and the specific neural regulatory mechanisms underlying such compensation remains largely unclear. Here, by utilizing a synchronized EEG-fNIRS test, we investigated the neural oscillatory characteristics of the theta band and synchronous hemodynamic changes in the frontal cortex during a speech recognition task in noise. The study included healthy older adults (n = 26, aged 65.4 ± 2.8), those with mild hearing loss (n = 26, aged 66.3 ± 3.8), and those with moderate to severe hearing loss (n = 26, aged 67.5 ± 3.7). Results showed that, relative to healthy older adults, older adults with ARHL exhibited lower activation and weakened theta band neural oscillations in the left dorsolateral prefrontal cortex (DLPFC) under noisy conditions, and this decreased activity correlated with high-frequency hearing loss. Meanwhile, we found that the connectivity of the frontoparietal network was significantly reduced, which might depress the top-down articulatory prediction function affecting speech recognition performance in ARHL older adults. The results suggested that healthy aging older adults might exhibit compensatory attentional resource recruitment through a top-down auditory-motor integration mechanism. In comparison, older adults with ARHL reflected decompensation of the left DLPFC involving the frontoparietal integration network during speech recognition tasks in noise.

Exploring Electrophysiological Responses to Hypnosis in Patients with Fibromyalgia

Background/Objectives: Hypnosis shows great potential for managing patients suffering from fibromyalgia and chronic pain. Several studies have highlighted its efficacy in improving pain, quality of life, and reducing psychological distress. Despite its known feasibility and efficacy, the mechanisms of action remain poorly understood. Building on these insights, this innovative study aims to assess neural activity during hypnosis in fibromyalgia patients using high-density electroencephalography (EEG) and self-reported measures. Methods: Thirteen participants with fibromyalgia were included in this study. EEG recordings were done during resting state and hypnosis conditions. After both conditions, levels of pain, comfort, absorption, and dissociation were assessed using a numerical rating scale. Time perception was collected via an open-ended question. The study was prospectively registered in the ClinicalTrials.gov public registry (NCT04263324). Results: Neural oscillations showed increased theta power during hypnosis in the left parietal and occipital electrodes, increased beta power in the frontal and left temporal electrodes, and increased slow-gamma power in the frontal and left parietal electrodes. Functional connectivity using pairwise-phase consistency measures showed decreased connectivity in the frontal electrodes during hypnosis. Graph-based measures, the node strength, and the cluster coefficient were lower in frontal electrodes in the slow-gamma bands during hypnosis compared to resting state. Key findings indicate significant changes in neural oscillations and brain functional connectivity, suggesting potential electrophysiological markers of hypnosis in this patient population.

Arginine vasopressin induces analgesic effects and inhibits pyramidal cells in the anterior cingulate cortex in spared nerve injured mice.

Neuropathic pain (NP) is a severe disease caused by a primary disease or lesion affecting the somatosensory nervous system. It`s reported that NP is related to the increased activity of glutamatergic pyramidal cells and changed neural oscillations in the anterior cingulate cortex (ACC). Arginine vasopressin (AVP), a neurohypophyseal hormone, has been shown to cause pain-alleviating effects when applied to peripheral system. However, the extent to which, and the mechanisms by which, AVP induces analgesic effects in the central nervous system remain unclear. In the present study, we observed that intranasal delivery of AVP inhibited mechanical pain, thermal pain and spontaneous pain sensitivity in mice with spared nerve injury. Meanwhile, AVP application exclusively reduced the FOS expression in the pyramidal cells but not interneurons in the ACC. In vivo electrophysiological recording of the ACC further showed that AVP application not only inhibited the theta oscillation in local field potential analysis, but also reduced the firing rate of spikes of pyramidal cells in the ACC in neuropathic pain mice. In summary, AVP induce analgesic effects by inhibiting neural theta oscillations and the spiking of pyramidal cells of the ACC in mice with neuropathic pain, which should provide new potential noninvasive methods for clinical treatment of chronic pain.

Neural Correlates of Psychedelic, Sleep, and Sedated States Support Global Theories of Consciousness.

Understanding neural mechanisms of consciousness remains a challenging question in neuroscience. A central debate in the field concerns whether consciousness arises from global interactions that involve multiple brain regions or focal neural activity, such as in sensory cortex. Additionally, global theories diverge between the Global Neuronal Workspace (GNW) hypothesis, which emphasizes frontal and parietal areas, and the Integrated Information Theory (IIT), which focuses on information integration within posterior cortical regions. To disentangle the global vs. local and frontoparietal vs. posterior dilemmas, we measured global functional connectivity and local neural synchrony with functional magnetic resonance imaging (fMRI) data across a spectrum of conscious states in humans induced by psychedelics, sleep, and deep sedation. We found that psychedelic states are associated with increased global functional connectivity and decreased local neural synchrony. In contrast, non-REM sleep and deep sedation displayed the opposite pattern, suggesting that consciousness arises from global brain network interactions rather than localized activity. This mirror-image pattern between enhanced and diminished states was observed in both anterior-posterior (A-P) and posterior-posterior (P-P) brain regions but not within the anterior part of the brain alone. Moreover, anterior transmodal regions played a key role in A-P connectivity, while both posterior transmodal and posterior unimodal regions were critical for P-P connectivity. Overall, these findings provide empirical evidence supporting global theories of consciousness in relation to varying states of consciousness. They also bridge the gap between two prominent theories, GNW and IIT, by demonstrating how different theories can converge on shared neuronal mechanisms.