Electrophysiological correlates of sustained conscious perception.

Previous research on the neural correlates of consciousness (NCC) in visual perception revealed an early event-related potential (ERP), the visual awareness negativity (VAN), to be associated with stimulus awareness. However, due to the use of brief stimulus presentations in previous studies, it remains unclear whether awareness-related negativities represent a transient onset-related response or correspond to the duration of a conscious percept. Studies are required that allow prolonged stimulus presentation under aware and unaware conditions. The present ERP study aimed to tackle this challenge by using a novel stimulation design. Male and female human participants (n = 62) performed a visual task while task-irrelevant line stimuli were presented in the background for either 500 or 1000 ms. The line stimuli sometimes contained a face, which needed so-called visual one-shot learning to be seen. Half of the participants were informed about the presence of the face, resulting in faces being perceived by the informed but not by the uninformed participants. Comparing ERPs between the informed and uninformed group revealed an enhanced negativity over occipitotemporal electrodes that persisted for the entire duration of stimulus presentation. Our results suggest that sustained visual awareness negativities (SVAN) are associated with the duration of stimulus presentation.

Shared EEG correlates between non-REM parasomnia experiences and dreams.

Sleepwalking and related parasomnias result from incomplete awakenings out of non-rapid eye movement sleep. Behavioral episodes can occur without consciousness or recollection, or in relation to dream-like experiences. To understand what accounts for these differences in consciousness and recall, here we recorded parasomnia episodes with high-density electroencephalography (EEG) and interviewed participants immediately afterward about their experiences. Compared to reports of no experience (19%), reports of conscious experience (56%) were preceded by high-amplitude EEG slow waves in anterior cortical regions and activation of posterior cortical regions, similar to previously described EEG correlates of dreaming. Recall of the content of the experience (56%), compared to no recall (25%), was associated with higher EEG activation in the right medial temporal region before movement onset. Our work suggests that the EEG correlates of parasomnia experiences are similar to those reported for dreams and may thus reflect core physiological processes involved in sleep consciousness.

Autonomous Sensory Meridian Response (ASMR) and the Functions of Consciousness.

"Autonomous Sensory Meridian Response" (ASMR) refers to a sensory-emotional experience that was first explicitly identified and named within the past two decades in online discussion boards. Since then, there has been mounting psychological and neural evidence of a clustering of properties common to the phenomenon of ASMR, including convergence on the set of stimuli that trigger the experience, the properties of the experience itself, and its downstream effects. Moreover, psychological instruments have begun to be developed and employed in an attempt to measure it. Based on this empirical work, we make the case that despite its nonscientific origins, ASMR is a good candidate for being a real kind in the cognitive sciences. The phenomenon appears to have a robust causal profile and may also have an adaptive evolutionary history. We also argue that a more thorough understanding of the distinctive type of phenomenal experience involved in an ASMR episode can shed light on the functions of consciousness, and ultimately undermine certain "cognitive" theories of consciousness. We conclude that ASMR should be the subject of more extensive scientific investigation, particularly since it may also have the potential for therapeutic applications.

Re-awakening the brain: Forcing transitions in disorders of consciousness by external in silico perturbation.

A fundamental challenge in neuroscience is accurately defining brain states and predicting how and where to perturb the brain to force a transition. Here, we investigated resting-state fMRI data of patients suffering from disorders of consciousness (DoC) after coma (minimally conscious and unresponsive wakefulness states) and healthy controls. We applied model-free and model-based approaches to help elucidate the underlying brain mechanisms of patients with DoC. The model-free approach allowed us to characterize brain states in DoC and healthy controls as a probabilistic metastable substate (PMS) space. The PMS of each group was defined by a repertoire of unique patterns (i.e., metastable substates) with different probabilities of occurrence. In the model-based approach, we adjusted the PMS of each DoC group to a causal whole-brain model. This allowed us to explore optimal strategies for promoting transitions by applying off-line in silico probing. Furthermore, this approach enabled us to evaluate the impact of local perturbations in terms of their global effects and sensitivity to stimulation, which is a model-based biomarker providing a deeper understanding of the mechanisms underlying DoC. Our results show that transitions were obtained in a synchronous protocol, in which the somatomotor network, thalamus, precuneus and insula were the most sensitive areas to perturbation. This motivates further work to continue understanding brain function and treatments of disorders of consciousness.

Reduced processing of afforded actions while observing mental content as ongoing mental phenomena.

While consciousness is typically considered equivalent to mental contents, certain meditation practices-including open monitoring (OM)-are said to enable a unique conscious state where meditators can experience mental content from a de-reified perspective as "ongoing phenomena." Phenomenologically, such a state is considered as reduction of intentionality, the mental act upon mental content. We hypothesised that this de-reified state would be characterised by reduced mental actional processing of affording objects. We recruited two groups of participants, meditators with long-term experience in cultivating a de-reified state, and demographically-matched novice meditators. Participants performed a task with images in two configurations-where objects did (high-affordance) and did not imply actions (low-affordance)-following both a baseline and OM-induced de-reified state, along with EEG recordings. While long-term meditators exhibited preferential processing of high-affordance images compared to low-affordance images during baseline, such an effect was abolished during the OM state, as hypothesised. For novices, however, the high-affordance configuration was preferred over the low-affordance one both during baseline and OM. Perceptual durations of objects across conditions positively correlated with the degree of µ-rhythm desynchronization, indicating that neural processing of affordance impacted perceptual awareness. Our results indicate that OM styles of meditation may help in mentally decoupling otherwise automatic cognitive processing of mental actions by affording objects.

The enlightenment.

The period begins with the work of Richard Wiseman who was associated with royalists in the English Civil War. A little later Dionis was the first to note a relationship between a disturbance of consciousness and extravasation of blood. This notion was continued and expanded by Le Dran, Pott, and Benjamin Bell, with Pott providing a pathophysiological explanation of the phenomenon. Daniel Turner commented on how confusing Galenic teaching was on the topic of consciousness. Heister further emphasized the relationship between clinical disturbance and the extravasation of blood. Le Dran stated that symptoms following cranial trauma related to cerebral injury, an opinion supported by Pott and never subsequently challenged. Latta noted the importance of meningeal arteries in the development of hematomas. Benjamin Bell considered trepanation only appropriate for a clinical deterioration consistent with hemorrhagic extravasation. The two Irish surgeons made it clear that the presence of periosteal separation was not in fact a reliable indicator of an extravasation. The most striking change of instruments was disappearance of simple straight trepans with non-perforating tips for making small holes safely. The use of scrapers gradually declined as did that of lenticulars. There was a great debate about the value of a conical rather than a cylindrical crown. The former was said to be safer. But this opinion faded and the cylindrical crown became preferred. Another improvement in technique involved the use of constant probing to check the depth of the drilled groove.

Multimodal MRI reveals brainstem connections that sustain wakefulness in human consciousness.

Consciousness is composed of arousal (i.e., wakefulness) and awareness. Substantial progress has been made in mapping the cortical networks that underlie awareness in the human brain, but knowledge about the subcortical networks that sustain arousal in humans is incomplete. Here, we aimed to map the connectivity of a proposed subcortical arousal network that sustains wakefulness in the human brain, analogous to the cortical default mode network (DMN) that has been shown to contribute to awareness. We integrated data from ex vivo diffusion magnetic resonance imaging (MRI) of three human brains, obtained at autopsy from neurologically normal individuals, with immunohistochemical staining of subcortical brain sections. We identified nodes of the proposed default ascending arousal network (dAAN) in the brainstem, hypothalamus, thalamus, and basal forebrain. Deterministic and probabilistic tractography analyses of the ex vivo diffusion MRI data revealed projection, association, and commissural pathways linking dAAN nodes with one another and with DMN nodes. Complementary analyses of in vivo 7-tesla resting-state functional MRI data from the Human Connectome Project identified the dopaminergic ventral tegmental area in the midbrain as a widely connected hub node at the nexus of the subcortical arousal and cortical awareness networks. Our network-based autopsy methods and connectivity data provide a putative neuroanatomic architecture for the integration of arousal and awareness in human consciousness.

Correlation between Thalamocortical Tract and Default Mode Network with Consciousness Levels in Hypoxic-Ischemic Brain Injury Patients: A Comparative Study Using the Coma Recovery Scale-Revised.

BACKGROUND The thalamocortical tract (TCT) links nerve fibers between the thalamus and cerebral cortex, relaying motor/sensory information. The default mode network (DMN) comprises bilateral, symmetrical, isolated cortical regions of the lateral and medial parietal and temporal brain cortex. The Coma Recovery Scale-Revised (CRS-R) is a standardized neurobehavioral assessment of disorders of consciousness (DOC). In the present study, 31 patients with hypoxic-ischemic brain injury (HI-BI) were compared for changes in the TCT and DMN with consciousness levels assessed using the CRS-R. MATERIAL AND METHODS In this retrospective study, 31 consecutive patients with HI-BI (17 DOC,14 non-DOC) and 17 age- and sex-matched normal control subjects were recruited. Magnetic resonance imaging was used to diagnose HI-BI, and the CRS-R was used to evaluate consciousness levels at the time of diffusion tensor imaging (DTI). The fractional anisotropy (FA) values and tract volumes (TV) of the TCT and DMN were compared. RESULTS In patients with DOC, the FA values and TV of both the TCT and DMN were significantly lower compared to those of patients without DOC and the control subjects (p<0.05). When comparing the non-DOC and control groups, the TV of the TCT and DMN were significantly lower in the non-DOC group (p<0.05). Moreover, the CRS-R score had strong positive correlations with the TV of the TCT (r=0.501, p<0.05), FA of the DMN (r=0.532, p<0.05), and TV of the DMN (r=0.501, p<0.05) in the DOC group. CONCLUSIONS This study suggests that both the TCT and DMN exhibit strong correlations with consciousness levels in DOC patients with HI-BI.

A measure centrality index for systematic empirical comparison of consciousness theories.

Consciousness science is marred by disparate constructs and methodologies, making it challenging to systematically compare theories. This foundational crisis casts doubts on the scientific character of the field itself. Addressing it, we propose a framework for systematically comparing consciousness theories by introducing a novel inter-theory classification interface, the Measure Centrality Index (MCI). Recognizing its gradient distribution, the MCI assesses the degree of importance a specific empirical measure has for a given consciousness theory. We apply the MCI to probe how the empirical measures of the Global Neuronal Workspace Theory (GNW), Integrated Information Theory (IIT), and Temporospatial Theory of Consciousness (TTC) would fare within the context of the other two. We demonstrate that direct comparison of IIT, GNW, and TTC is meaningful and valid for some measures like Lempel-Ziv Complexity (LZC), Autocorrelation Window (ACW), and possibly Mutual Information (MI). In contrast, it is problematic for others like the anatomical and physiological neural correlates of consciousness (NCC) due to their MCI-based differential weightings within the structure of the theories. In sum, we introduce and provide proof-of-principle of a novel systematic method for direct inter-theory empirical comparisons, thereby addressing isolated evolution of theories and confirmatory bias issues in the state-of-the-art neuroscience of consciousness.

Induction of altered states of consciousness during Floatation-REST is associated with the dissolution of body boundaries and the distortion of subjective time.

Floatation-REST (Reduced Environmental Stimulation Therapy) minimizes stimulation of the nervous system by immersing subjects in an environment without sound or light while they effortlessly float in thermoneutral water supersaturated with Epsom salt. Here we investigated the relationship between altered states of consciousness (ASC) and its association with the affective changes induced by Floatation-REST. Using a within-subject crossover design, 50 healthy subjects were randomized to 60 min of Floatation-REST or 60 min of Bed-REST (an active control condition that entailed lying supine on a warm waterbed in a dark and quiet room). Following Floatation-REST, subjects felt significantly more relaxed, less anxious, and less tired than after Bed-REST. Floatation-REST also induced significantly more pronounced ASC characterized by the dissolution of body boundaries and the distortion of subjective time. The loss of body boundaries mediated the loss of anxiety, revealing a novel mechanism by which Floatation-REST exerts its anxiolytic effect.

Late Positivity Correlates with Subjective Reports: Evidence from the Low-frequency and High-frequency Reporting Tasks.

Identifying the neural correlates of consciousness (NCCs) is an important way to understand the fundamental nature of consciousness. By recording event-related potentials (ERPs) using EEG, researchers have found three potential electrophysiological NCCs: early positive correlate of consciousness (enhanced P1), visual awareness negativity (VAN), and late positivity (LP). However, LP may reflect post-perceptual processing associated with subjective reports rather than consciousness per se. The present experiment investigated the relationship between LP and subjective reports. We adopted two subjective reporting tasks that differed in the requirement for subjective reports. In the low-frequency reporting task, participants needed to report whether they saw the target picture in 25% of trials, whereas in the high-frequency reporting task, participants needed to report whether they saw the target picture in each trial. Behavioral results showed that the hit rates were lower and false alarm rates were higher on reporting trials in low-frequency reporting tasks than on reporting trials in high-frequency reporting tasks. Unexpectedly, VAN was larger on reporting trials in the low-frequency reporting task than on reporting trials in the high-frequency reporting task. Importantly, our ERP results showed that LP was larger on reporting trials in the high-frequency reporting task than on reporting trials in the low-frequency reporting task. Thus, our findings indicated that when the frequency of reports was increased, the task relevance of the stimuli increased, which led to larger LP amplitudes. These findings suggest that LP correlates with subjective reports.

Consciousness and the Dying Brain.

The near-death experience has been reported since antiquity and is often characterized by the perception of light, interactions with other entities, and life recall. Near-death experiences can occur in a variety of situations, but they have been studied systematically after in-hospital cardiac arrest, with an incidence of 10 to 20%. Long attributed to metaphysical or supernatural causes, there have been recent advances in understanding the neurophysiologic basis of this unique category of conscious experience. This article reviews the epidemiology and neurobiology of near-death experiences, with a focus on clinical and laboratory evidence for a surge of neurophysiologic gamma oscillations and cortical connectivity after cardiac and respiratory arrest.

The mental health benefits and costs of critical consciousness: A longitudinal investigation of the co-occurring positive and negative effects of critical consciousness among sexual minorities.

Critical consciousness is a powerful tool for individuals from marginalized groups to transcend their oppressive conditions through engagement in critical reflection, motivation, and action. Nonetheless, the mental health benefits and costs of critical consciousness have received limited research attention. The present study utilized a longitudinal research design to explore the positive and negative relationships between critical consciousness and mental health among sexual minority individuals in different developmental stages. A total of 636 sexual minority individuals were involved in the baseline study and were asked to complete a follow-up questionnaire after one year. The results demonstrated a co-occurrence of positive and negative effects of critical consciousness on mental health among sexual minority individuals across time. On the one hand, critical consciousness was associated with better mental health outcomes through the mediation of internalized oppression and community connectedness. Specifically, critical consciousness was associated with reduced internalized oppression, which in turn was linked to lower levels of emotional distress. Critical consciousness was also associated with heightened levels of community connectedness, which in turn was associated with improved well-being. On the other hand, the results revealed a positive direct effect of critical consciousness on emotional distress, after controlling for internalized oppression and community connectedness. Notably, developmental stage moderated the relationship between critical consciousness and well-being. A negative association between critical consciousness and well-being was observed among sexual minority youth, whereas no such association was found among sexual minority adults. While the study highlights that critical consciousness can be a pedagogical and therapeutic tool for the liberation and empowerment of sexual minority individuals, it is equally important to acknowledge the potential risks associated with critical consciousness. Striking a balance between critical consciousness and self-care is crucial for sustaining meaningful engagement in the pursuit of social change.

[The DoC-feeling scale, a paramedical assessment tool improving the diagnostic accuracy of the state of consciousness of non-communicative patients]. / L'échelle DoC-feeling, un outil d'évaluation paramédical améliorant la précision diagnostique de l'état de conscience des patients non communicants.

The Neurological Intensive Care Unit (ICU) at Pitié-Salpêtrière Hospital cares for patients with severe brain injuries, which can lead to acute or chronic disorders of consciousness. To assess the patient's state of consciousness, the team relies on precise clinical examination. This article presents the assessment tools used to establish the patient's prognosis.

Bio-Psycho-Spiritual Perspectives on Psychedelics: Clinical and Ethical Implications.

Psychedelics have again become a subject of widespread interest, owing to the reinvigoration of research into their traditional uses, possible medical applications, and social implications. As evidence for psychedelics' clinical potential mounts, the field has increasingly focused on searching for mechanisms to explain the effects of psychedelics and therapeutic efficacy of psychedelic-assisted therapy (PAT). This paper reviews three general frameworks that encompass several prominent models for understanding psychedelics' effects-specifically, neurobiological, psychological, and spiritual frameworks. Following our review, the implications of each framework for ethics and professional competencies in the implementation of psychedelics as medicines are explored. We suggest that interdisciplinary education may be necessary to improve communication between researchers, develop models that effectively incorporate multiple levels of analysis, and facilitate collaboration between professionals with diverse backgrounds in the implementation of psychedelic medicines. We also address pitfalls associated with overemphasis on neuro-mechanisms, risks associated with instigating vulnerable states of consciousness, and hurdles associated with the integration of spiritual frameworks in medicine. Ultimately, as psychedelics push the boundaries of explanatory frameworks focused on one level of analysis, developing new and more useful models to reflect knowledge being produced in this field should be a central aim of psychedelic science going forward.

Valuing the Acute Subjective Experience.

Psychedelics, including psilocybin, and other consciousness-altering compounds such as 3,4-methylenedioxymethamphetamine (MDMA), currently are being scientifically investigated for their potential therapeutic uses, with a primary focus on measurable outcomes: for example, alleviation of symptoms or increases in self-reported well-being. Accordingly, much recent discussion about the possible value of these substances has turned on estimates of the magnitude and duration of persisting positive effects in comparison to harms. However, many have described the value of a psychedelic experience with little or no reference to such therapeutic benefits, instead seeming to find the experience valuable in its own right. How can we make sense of such testimony? Could a psychedelic experience be valuable even if there were no persisting beneficial effects? If so, how? Using the concept of psychological richness, combined with insights from the philosophy of aesthetics and the enhancement literature, this essay explores potential sources of value in the acute subjective experience, apart from the value derived from persisting beneficial effects.

COVID-19-induced acute loss of consciousness in Marchiafava-Bignami disease: a case report.

Among the various manifestations of COVID-19, the neurological implications of SARS-CoV-2 infection are of significant concern. Marchiafava-Bignami disease (MBD), a neurodegenerative disorder, exhibits a clinical spectrum ranging from mild progressive dementia in its chronic form to states of acute coma and varied mortality rates. Acute MBD primarily occurs in chronic alcoholics and malnourished individuals and is characterized by sudden loss of consciousness, seizures, confusion, and psychosis. We herein report a case of MBD presenting as acute loss of consciousness after the development of COVID-19. The patient presented with a history of fever and upper respiratory infection and was diagnosed with SARS-CoV-2 infection. He developed a neurological syndrome characterized by altered consciousness and convulsions, and brain magnetic resonance imaging revealed abnormal signals in the corpus callosum and frontoparietal lobes. Considering his alcohol intake history and the absence of other differential diagnoses, we diagnosed him with acute MBD triggered by COVID-19. After high-dose vitamin B1 and corticosteroid therapy, his clinical symptoms improved. In this case, we observed a temporal sequence between the development of COVID-19 and acute exacerbation of MBD. This case adds to the mounting evidence suggesting the potential effect of SARS-CoV-2 on the neurological system.

Unconscious prioritization for face-to-face people.

One central question in the scientific and philosophical study of consciousness is regarding the scope of human consciousness. There is a lively debate as to whether high-level information integration is necessarily dependent on consciousness. This study presents a new form of unconscious integration based on the facingness between two individuals. Using a breaking continuous flash suppression paradigm, Experiments 1-3 found that two facing human heads got a privilege in breaking into awareness compared to nonfacing pairs. Experiments 4 and 5 demonstrated that the breakthrough difference between facing and nonfacing pairs could not be attributed to low-level or mid-level factors. Experiments 6, 7a, and 7b showed that the unconscious priority of facing pairs was significantly diminished when the holistic processing of the two agents was disrupted. Experiments 8-11 demonstrated that the advantage of facing pairs was only observable for human agents and not for daily objects, directional arrows, or nonhuman animals. These findings have critical implications for better understanding the scope of human consciousness and the origins of social vision. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Late Middle Ages-Europe.

At the end of the late Middle Ages, there had been changes in indications for surgery, with prophylactic trepanation falling out of favor. The management of wounds and the methods for opening the cranium had become fairly standardized. Narrow non-plunging trepans were the preferred drills, and cranial openings were widened by the use of multiple drill holes connected with chisels of which the lenticular was preferred. Concerns about damaging the dura led Theodoric to delay trepanation until the clinical changes reflected separation of the dura from the cranium, at least in his view. Draining pus remained the main indication for trepanation. In no case was the level of consciousness considered in determining the need to open the cranium.