Nature
August 1, 2024
Joshua S. Siegel, Subha Subramanian, Demetrius Perry et al.
241 citations
A single high dose of psilocybin (25 mg) massively disrupts functional connectivity in the human brain, causing more than threefold greater change than methylphenidate (40 mg). These changes are driven by desynchronization across spatial scales, dissolving network distinctions by reducing correlations within and anticorrelations between networks. The strongest effects occur in the default mode network, which is connected to the anterior hippocampus and is thought to create the sense of space, time, and self. Individual differences in connectivity changes are strongly linked to the subjective psychedelic experience. A persistent decrease in connectivity between the anterior hippocampus and default mode network lasts for weeks, suggesting a neuroanatomical correlate of the therapeutic and proplasticity effects of psychedelics.
Trends in Cognitive Sciences
October 1, 2023
Tim Bayne, Joel Frohlich, R. Cusack et al.
Evidence from studies of functional network connectivity, attention, multimodal integration, and cortical responses to global oddballs suggests that consciousness is likely present in early infancy and may even occur before birth. Recent research is beginning to provide clues about both the content and structure of infant consciousness.
Neuroimage
June 1, 2023
Joel Frohlich, Tim Bayne, Julia S Crone et al.
Consciousness likely cannot begin before the establishment of thalamocortical connectivity at 26 weeks gestation, as this system is necessary for subjective experience according to most theoretical frameworks. To determine when consciousness emerges after this point, the authors advocate developing a sensory perturbational complexity index (sPCI) using auditory, visual, or olfactory cortical perturbations—rather than electromagnetic ones—to estimate the perinatal brain's state of consciousness. Techniques such as fMRI, EEG, and MEG can be used in both newborn and fetal studies, with the womb offering a more controlled environment than the cradle for such investigations.
Developmental Cognitive Neuroscience
June 1, 2021
Julia Moser, Franziska Schleger, Magdalene Weiss et al.
Fetuses in the last trimester of pregnancy show signs of hierarchical rule learning, a cognitive ability linked to conscious processing. Using fetal magnetoencephalography on 56 healthy fetuses between gestational weeks 25 and 40, an auditory oddball paradigm with first- and second-order regularities was presented. Brain responses to standard versus deviant tones indicated formation of a memory trace for the second-order regularity, an ability that develops with physiological brain maturation and was reliably present only in fetuses older than week 35. Autonomic nervous system activity, replicating findings in newborns, showed the importance of activity state for cognitive processes. These results support the assumption that fetuses in the last weeks of gestation can consciously process stimuli from outside the womb.
Frontiers in Systems Neuroscience
January 1, 2019
Julia Moser, Siouar Bensaid, Eleni Kroupi et al.
Information-based metrics of neural activity can help quantify consciousness before and shortly after birth. Using fetal magnetoencephalography (fMEG) in human fetuses and neonates, researchers evaluated measures of entropy, compressibility, and fractality. Lempel-Ziv-Complexity (LZC) was the most practical metric because it is unequivocal and requires low computational effort, whereas fractality and entropy measures need more parameter adjustments. Comparing a brain-activity channel with a control channel in neonates showed significant differences in most complexity metrics, serving as proof of concept. For fetal data, results were less clear, possibly due to leftover maternal signals. The inconsistency across metrics highlights challenges in using complexity metrics as neural correlates of consciousness.