GABAergic neurons of anterior thalamic reticular nucleus regulate states of consciousness in propofol- and isoflurane-mediated general anesthesia.

BACKGROUND: The thalamus system plays critical roles in the regulation of reversible unconsciousness induced by general anesthetics, especially the arousal stage of general anesthesia (GA). But the function of thalamus in GA-induced loss of consciousness (LOC) is little known. The thalamic reticular nucleus (TRN) is the only GABAergic neurons-composed nucleus in the thalamus, which is composed of parvalbumin (PV) and somatostatin (SST)-expressing GABAergic neurons. The anterior sector of TRN (aTRN) is indicated to participate in the induction of anesthesia, but the roles remain unclear. This study aimed to reveal the role of the aTRN in propofol and isoflurane anesthesia. METHODS: We first set up c-Fos straining to monitor the activity variation of aTRNPV and aTRNSST neurons during propofol and isoflurane anesthesia. Subsequently, optogenetic tools were utilized to activate aTRNPV and aTRNSST neurons to elucidate the roles of aTRNPV and aTRNSST neurons in propofol and isoflurane anesthesia. Electroencephalogram (EEG) recordings and behavioral tests were recorded and analyzed. Lastly, chemogenetic activation of the aTRNPV neurons was applied to confirm the function of the aTRN neurons in propofol and isoflurane anesthesia. RESULTS: c-Fos straining showed that both aTRNPV and aTRNSST neurons are activated during the LOC period of propofol and isoflurane anesthesia. Optogenetic activation of aTRNPV and aTRNSST neurons promoted isoflurane induction and delayed the recovery of consciousness (ROC) after propofol and isoflurane anesthesia, meanwhile chemogenetic activation of the aTRNPV neurons displayed the similar effects. Moreover, optogenetic and chemogenetic activation of the aTRN neurons resulted in the accumulated burst suppression ratio (BSR) during propofol and isoflurane GA, although they represented different effects on the power distribution of EEG frequency. CONCLUSION: Our findings reveal that the aTRN GABAergic neurons play a critical role in promoting the induction of propofol- and isoflurane-mediated GA.

Dismantling the colonial mindset and becoming "Gender AWAke": From gendered complicity to embodied praxis.

The purpose of this article is to delineate the nature of the colonial mindset, which perpetuates gendered settler colonial structures of historical oppression in research and practice. By connecting a critical consciousness and living in alignment with agility (AWA), this work explicates pathways from gendered complicity to embodying praxis-or becoming gender AWAke. This article begins by describing the nature of the colonial mindset. Second, I critically examine the dominant discourse institutionalized by Western psychology. Third, I introduce the FHORT and critically analyze how the colonial mindset has affected and driven violence against Indigenous women. Examining how settler colonial structural sexism in its heteropatriarchal and heteropaternalistic forms has become imposed upon the lives of Indigenous women and gender-expansive peoples exposes subjugated knowledges; it provides an empirical scaffolding for people to become critically conscious of dominant gender norms that apply to people, institutions, and society more broadly. Finally, I propose living AWAke for personal and collective liberation.

Neural markers of reduced arousal and consciousness in mild cognitive impairment.

OBJECTIVES: People with Alzheimer's Disease (AD) experience changes in their level and content of consciousness, but there is little research on biomarkers of consciousness in pre-clinical AD and Mild Cognitive Impairment (MCI). This study investigated whether levels of consciousness are decreased in people with MCI. METHODS: A multi-site site magnetoencephalography (MEG) dataset, BIOFIND, comprising 83 people with MCI and 83 age matched controls, was analysed. Arousal (and drowsiness) was assessed by computing the theta-alpha ratio (TAR). The Lempel-Ziv algorithm (LZ) was used to quantify the information content of brain activity, with higher LZ values indicating greater complexity and potentially a higher level of consciousness. RESULTS: LZ was lower in the MCI group versus controls, indicating a reduced level of consciousness in MCI. TAR was higher in the MCI group versus controls, indicating a reduced level of arousal (i.e. increased drowsiness) in MCI. LZ was also found to be correlated with mini-mental state examination (MMSE) scores, suggesting an association between cognitive impairment and level of consciousness in people with MCI. CONCLUSIONS: A decline in consciousness and arousal can be seen in MCI. As cognitive impairment worsens, measured by MMSE scores, levels of consciousness and arousal decrease. These findings highlight how monitoring consciousness using biomarkers could help understand and manage impairments found at the preclinical stages of AD. Further research is needed to explore markers of consciousness between people who progress from MCI to dementia and those who do not, and in people with moderate and severe AD, to promote person-centred care.

The influence of spatial and temporal attention on visual awareness-a behavioral and ERP study.

Whether attention is a prerequisite of perceptual awareness or an independent and dissociable process remains a matter of debate. Importantly, understanding the relation between attention and awareness is probably not possible without taking into account the fact that both are heterogeneous and multifaceted mechanisms. Therefore, the present study tested the impact on visual awareness of two attentional mechanisms proposed by the Posner model: temporal alerting and spatio-temporal orienting. Specifically, we evaluated the effects of attention on the perceptual level, by measuring objective and subjective awareness of a threshold-level stimulus; and on the neural level, by investigating how attention affects two postulated event-related potential correlates of awareness. We found that alerting and orienting mechanisms additively facilitate perceptual consciousness, with activation of the latter resulting in the most vivid awareness. Furthermore, we found that late positivity is unlikely to constitute a neural correlate of consciousness as its amplitude was modulated by both attentional mechanisms, but early visual awareness negativity was independent of the alerting and orienting mechanisms. In conclusion, our study reveals a nuanced relationship between attention and awareness; moreover, by investigating the effect of the alerting mechanism, this study provides insights into the role of temporal attention in perceptual consciousness.

Transient brain activity dynamics discriminate levels of consciousness during anesthesia.

The awake mammalian brain is functionally organized in terms of large-scale distributed networks that are constantly interacting. Loss of consciousness might disrupt this temporal organization leaving patients unresponsive. We hypothesize that characterizing brain activity in terms of transient events may provide a signature of consciousness. For this, we analyze temporal dynamics of spatiotemporally overlapping functional networks obtained from fMRI transient activity across different anesthetics and levels of anesthesia. We first show a striking homology in spatial organization of networks between monkeys and humans, indicating cross-species similarities in resting-state fMRI structure. We then track how network organization shifts under different anesthesia conditions in macaque monkeys. While the spatial aspect of the networks is preserved, their temporal dynamics are highly affected by anesthesia. Networks express for longer durations and co-activate in an anesthetic-specific configuration. Additionally, hierarchical brain organization is disrupted with a consciousness-level-signature role of the default mode network. In conclusion, large-scale brain network temporal dynamics capture differences in anesthetic-specific consciousness-level, paving the way towards a clinical translation of these cortical signature.

Observing the suppression of individual aversive memories from conscious awareness.

When reminded of an unpleasant experience, people often try to exclude the unwanted memory from awareness, a process known as retrieval suppression. Here we used multivariate decoding (MVPA) and representational similarity analyses on EEG data to track how suppression unfolds in time and to reveal its impact on item-specific cortical patterns. We presented reminders to aversive scenes and asked people to either suppress or to retrieve the scene. During suppression, mid-frontal theta power within the first 500 ms distinguished suppression from passive viewing of the reminder, indicating that suppression rapidly recruited control. During retrieval, we could discern EEG cortical patterns relating to individual memories-initially, based on theta-driven visual perception of the reminders (0 to 500 ms) and later, based on alpha-driven reinstatement of the aversive scene (500 to 3000 ms). Critically, suppressing retrieval weakened (during 360 to 600 ms) and eventually abolished item-specific cortical patterns, a robust effect that persisted until the reminder disappeared (780 to 3000 ms). Representational similarity analyses provided converging evidence that retrieval suppression weakened the representation of target scenes during the 500 to 3000 ms reinstatement window. Together, rapid top-down control during retrieval suppression abolished cortical patterns of individual memories, and precipitated later forgetting. These findings reveal a precise chronometry on the voluntary suppression of individual memories.

Guía de tratamiento de la alteración aguda del estado mental. Academia Iberoamericana de Neurología Pediátrica / Guide for the treatment of acute altered mental status. Iberoamerican Academy of Pediatric Neurology

La alteración aguda del estado mental en pediatría se refiere a un cambio repentino y significativo en la función cerebral y el nivel de conciencia de un niño. Puede manifestarse como confusión, desorientación, agitación, letargo o incluso pérdida de la conciencia. Esta condición es una emergencia médica, y requiere una evaluación y una atención inmediatas. Existen diversas causas de alteración aguda del estado mental en niños, algunas de las cuales incluyen infecciones del sistema nervioso central, como la meningitis o la encefalitis, los traumatismos craneoencefálicos, los trastornos metabólicos, las convulsiones o las intoxicaciones, entre otras. Este estudio tuvo como objetivo analizar, preparar y calificar la bibliografía actual para determinar las mejores recomendaciones sobre el tratamiento ante casos de alteración aguda del estado mental en pediatría de diferentes causas. El estudio se basó en la calificación de expertos en el campo para poder determinar la calificación de las recomendaciones, además de ser sometido a la revisión por parte del comité científico de la Academia Iberoamericana de Neurología Pediátrica. Nuestra guía representa una ayuda para el tratamiento de este síntoma inespecífico desde un enfoque básico y avanzado, aplicable por cualquier neurólogo pediatra.(AU)

In pediatric patients, an acute altered mental status refers to a sudden and significant change in a child’s brain function and level of consciousness. It may manifest as confusion, disorientation, agitation, lethargy or even a loss of consciousness. This condition is a medical emergency, and requires immediate evaluation and attention. There are several causes of acute altered mental status in children, including infections of the central nervous system such as meningitis or encephalitis, traumatic brain injury, metabolic disorders, seizures and poisoning, among others. The aim of this study was to analyse, prepare and classify the current literature in order to determine the best recommendations for the treatment of cases of acute altered mental status with various causes in pediatric patients. The study was based on opinions from experts in the field in order to classify the recommendations, and was submitted to the scientific committee of the Iberoamerican Academy of Pediatric Neurology for review. Our guide is an aid for the treatment of this non-specific symptom based on a basic and advanced approach, which can be applied by any pediatric neurologist.(AU)

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.

Developmental changes of bodily self-consciousness in adolescent girls.

The body and the self change markedly during adolescence, but how does bodily self-consciousness, the pre-reflexive experience of being a bodily subject, change? We addressed this issue by studying embodiment towards virtual avatars in 70 girls aged 10-17 years. We manipulated the synchrony between participants' and avatars' touch or movement, as well as the avatar visual shape or size relative to each participant's body. A weaker avatar's embodiment in case of mismatch between the body seen in virtual reality and the real body is indicative of a more robust bodily self-consciousness. In both the visuo-tactile and the visuo-motor experiments, asynchrony decreased ownership feeling to the same extent for all participants, while the effect of asynchrony on agency feeling increased with age. In the visuo-tactile experiment, incongruence in visual appearance did not affect agency feeling but impacted ownership, especially in older teenage girls. These findings highlight the higher malleability of bodily self-consciousness at the beginning of adolescence and suggest some independence between body ownership and agency.

A global neuronal workspace model of functional neurological disorders.

We introduce here a general model of Functional Neurological Disorders based on the following hypothesis: a Functional Neurological Disorder could correspond to a consciously initiated voluntary top-down process causing involuntary lasting consequences that are consciously experienced and subjectively interpreted by the patient as involuntary. We develop this central hypothesis according to Global Neuronal Workspace theory of consciousness, that is particularly suited to describe interactions between conscious and non-conscious cognitive processes. We then present a list of predictions defining a research program aimed at empirically testing their validity. Finally, this general model leads us to reinterpret the long-debated links between hypnotic suggestion and functional neurological disorders. Driven by both scientific and therapeutic goals, this theoretical paper aims at bringing closer the psychiatric and neurological worlds of functional neurological disorders with the latest developments of cognitive neuroscience 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.

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.

Christof Koch.

In this talk with Neuron, Christof Koch, a physicist and neuroscientist, advocates for a pragmatic program to track the footprints of consciousness in the brain and for team science, explains the recent pseudo-controversy regarding integrated information theory of consciousness, and speaks about the joy of exploring the mysteries around us.

Stanislas Dehaene.

Stanislas Dehaene is a cognitive neuroscientist elucidating the biological mechanisms that give rise to human perception and cognition. In a conversation with Neuron, he talks about his ongoing interest in consciousness research, the role of theory in neuroscience, and his current work on education and the science of learning.

Toward an interventional science of recovery after coma.

Recovery of consciousness after coma remains one of the most challenging areas for accurate diagnosis and effective therapeutic engagement in the clinical neurosciences. Recovery depends on preservation of neuronal integrity and evolving changes in network function that re-establish environmental responsiveness. It typically occurs in defined steps: it begins with eye opening and unresponsiveness in a vegetative state, then limited recovery of responsiveness characterizes the minimally conscious state, and this is followed by recovery of reliable communication. This review considers several points for novel interventions, for example, in persons with cognitive motor dissociation in whom a hidden cognitive reserve is revealed. Circuit mechanisms underlying restoration of behavioral responsiveness and communication are discussed. An emerging theme is the possibility to rescue latent capacities in partially damaged human networks across time. These opportunities should be exploited for therapeutic engagement to achieve individualized solutions for restoration of communication and environmental interaction across varying levels of recovery.

Can we detect consciousness in newborn infants?

Conscious experiences in infants remain poorly understood. In this NeuroView, Passos-Ferreira discusses recent evidence for and against consciousness in newborn babies. She argues that the weight of evidence from neuroimaging and behavioral studies supports the thesis that newborn infants are conscious.

Thalamic contributions to the state and contents of consciousness.

Consciousness can be conceptualized as varying along at least two dimensions: the global state of consciousness and the content of conscious experience. Here, we highlight the cellular and systems-level contributions of the thalamus to conscious state and then argue for thalamic contributions to conscious content, including the integrated, segregated, and continuous nature of our experience. We underscore vital, yet distinct roles for core- and matrix-type thalamic neurons. Through reciprocal interactions with deep-layer cortical neurons, matrix neurons support wakefulness and determine perceptual thresholds, whereas the cortical interactions of core neurons maintain content and enable perceptual constancy. We further propose that conscious integration, segregation, and continuity depend on the convergent nature of corticothalamic projections enabling dimensionality reduction, a thalamic reticular nucleus-mediated divisive normalization-like process, and sustained coherent activity in thalamocortical loops, respectively. Overall, we conclude that the thalamus plays a central topological role in brain structures controlling conscious experience.