Pharmacological agents that alter consciousness, including classic psychedelics and non-classic agents such as nitrous oxide, are known to affect multiple domains of conscious experience, including visual perception. While most neuroimaging studies rely on resting-state data to characterize altered states of consciousness, task-based approaches enable investigation of specific perceptual...
Nitrous oxide (N2O) produces perceptual alterations and changes in large-scale brain network organization, yet its effects on task-specific visual processing remain unclear. Given the prominence of visual alterations during psychedelic exposure, we investigated how subanesthetic N2O modulates functional connectivity during visual stimulation. Thirteen healthy adults completed a...
Background: Shamanism is a transcultural, heterogeneous worldview that is primarily concerned with human interaction with the spirit world. Foremost among the many services provided by practitioners of shamanism is the healing of the mind, body, and spirit. Methods: While most literature on shamanism consists of ethnographies of cultures that practice shamanism, the present literature search...
Previous studies have demonstrated acute changes in brain activity that occur during shamanic journeying-an ancient spiritual practice used for physical, psychological, and spiritual healing. However, the effect of shamanic journeying on other physiological measures, such as heart rate variability, remains unknown. We investigated changes in heart rate variability (HRV) during sessions of...
Despite the longstanding use of nitrous oxide and descriptions of its psychological effects more than a century ago, there is a paucity of neurobiological investigation of associated psychedelic experiences. We measure the brain's functional geometry (through analysis of cortical gradients) and temporal dynamics (through analysis of co-activation patterns) using human resting-state functional...
The neurobiology of the psychedelic experience is not fully understood. Identifying common brain network changes induced by both classical (i.e., acting at the 5-HT2 receptor) and non-classical psychedelics would provide mechanistic insight into state-specific characteristics. We analyzed whole-brain functional connectivity based on resting-state fMRI data in humans, acquired before and during...
Psychedelics have been recognized as model interventions for studying altered states of consciousness. However, few empirical studies of the shamanic state of consciousness, which is anecdotally similar to the psychedelic state, exist. We investigated the neural correlates of shamanic trance using high-density electroencephalography (EEG) in 24 shamanic practitioners and 24 healthy controls...
Detecting covert consciousness in behaviorally unresponsive patients by brain imaging is of great interest, but a reproducible model and evidence from independent sources is still lacking. Here we demonstrate the possibility of using general anesthetics in a within-subjects study design to test methods or statistical paradigms of assessing covert consciousness. Using noninvasive neuroimaging in...
BackgroundDespite its designation as a 'dissociative anaesthetic,' the dissociative and psychoactive effects of ketamine remain incompletely understood. The goal of this study was to characterise the subjective experiences and accompanying EEG changes with subanaesthetic doses of ketamine.MethodsHigh-density EEG was recorded in 15 human volunteers before, during, and after subanaesthetic...