Growing evidence from the dynamical analysis of functional neuroimaging data suggests that brain function can be understood as the exploration of a repertoire of metastable connectivity patterns ('functional brain networks'), which potentially underlie different mental processes.The present study characterizes how the brain's dynamical exploration of resting--state networks is rapidly modulated by intravenous infusion of psilocybin, a tryptamine psychedelic found in "magic mushrooms". We employed a data--driven approach to characterize recurrent functional connectivity patterns by focusing on the leading eigenvector of BOLD phase coherence at single--TR resolution. Recurrent BOLD phase--locking patterns (PL states) were assessed and statistically compared pre--and post--infusion of psilocybin in terms of their probability of occurrence and transition profiles. Results were validated using a placebo session.Recurrent BOLD PL states revealed high spatial overlap with canonical resting--state networks. Notably, a PL state forming a frontoparietal subsystem was strongly destabilized after psilocybin injection, with a concomitant increase in the probability of occurrence of another PL state characterized by global BOLD phase coherence. These findings provide Recently, a number of methodological approaches have been proposed to analyze BOLD connectivity dynamics at high temporal resolution (i.e., single volume / TR), focusing either on BOLD co--activation patterns (
The modern understanding of sleep is based on the classification of sleep into stages defined by their electroencephalography (EEG) signatures, but the underlying brain dynamics remain unclear. Here we aimed to move significantly beyond the current state-of-the-art description of sleep, and in particular to characterise the spatiotemporal complexity of whole-brain networks and state transitions during sleep. In order to obtain the most unbiased estimate of how whole-brain network states evolve through the human sleep cycle, we used a Markovian data-driven analysis of continuous neuroimaging data from 57 healthy participants falling asleep during simultaneous functional magnetic resonance imaging (fMRI) and EEG. This Hidden Markov Model (HMM) facilitated discovery of the dynamic choreography between different whole-brain networks across the wake-non-REM sleep cycle. Notably, our results reveal key trajectories to switch within and between EEG-based sleep stages, while highlighting the heterogeneities of stage N1 sleep and wakefulness before and after sleep.
Neurobiological models to explain vulnerability of major depressive disorder (MDD) are scarce and previous functional magnetic resonance imaging studies mostly examined “static” functional connectivity (FC). Knowing that FC constantly evolves over time, it becomes important to assess how FC dynamically differs in remitted‐MDD patients vulnerable for new depressive episodes. Using a recently developed method to examine dynamic FC, we characterized re‐emerging FC states during rest in 51 antidepressant‐free MDD patients at high risk of recurrence (≥2 previous episodes), and 35 healthy controls. We examined differences in occurrence, duration, and switching profiles of FC states after neutral and sad mood induction. Remitted MDD patients showed a decreased probability of an FC state (p < 0.005) consisting of an extensive network connecting frontal areas—important for cognitive control—with default mode network, striatum, and salience areas, involved in emotional and self‐referential processing. Even when this FC state was observed in patients, it lasted shorter (p < 0.005) and was less likely to switch to a smaller prefrontal–striatum network (p < 0.005). Differences between patients and controls decreased after sad mood induction. Further, the duration of this FC state increased in remitted patients after sad mood induction but not in controls (p < 0.05). Our findings suggest reduced ability of remitted‐MDD patients, in neutral mood, to access a clinically relevant control network involved in the interplay between externally and internally oriented attention. When recovering from sad mood, remitted recurrent MDD appears to employ a compensatory mechanism to access this FC state. This study provides a novel neurobiological profile of MDD vulnerability.
Prevailing theories hold that the insula is functionally organized along its caudal-to-rostral axis, with posterior regions coding lower-level sensory information, and anterior regions coding higherlevel stimulus significance relative to the body's homeostatic needs. Contrary to predictions of this model, the response of the taste-sensitive region of the caudal, but not rostral, insula to food images was directly related to the body's homeostatic state as indexed by levels of peripheral glucose.It is widely held that there exists along the insula a caudal-to-rostral functional organization, with more caudal regions representing primarily lower-level sensory interoceptive, gustatory, and somatosensory signals, and rostral regions contributing to higher-level cognition and emotion by integrating information about the body's homeostatic state with information represented in limbic and executive control networks 1,2 . Although the neuroanatomical connections between the insula and peripheral nervous system suggest that homeostatic integration occurs in more caudal insular regions, particularly in the mid-insula where gustatory and visceral information from cranial nerves VII, IX, and X first reaches the cerebral cortex via subcortical projections though the brainstem and thalamus 3 , it is also frequently asserted that anterior insula integrates this homeostatic information about the state of the body with higher cognitive functions.A direct empirical test of the prevailing account within a single group of individuals would require identifying a sensory stimulus that activates both rostral and caudal regions of the Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
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