Journal of The Royal Society Interface
October 29, 2014
Giovanni Petri, Paul Expert, Federico Turkheimer et al.
689 citations
Functional brain networks can be studied through homological cycles—topological objects that capture mesoscopic structure in weighted correlation networks. A new method, homological scaffolds, compactly represents these cycles and makes them amenable to standard network analysis. Applied to resting-state fMRI data from 15 healthy volunteers given placebo or psilocybin, the homological structure of brain activity changed dramatically after psilocybin, producing many transient, low-stability cycles and a few persistent ones absent under placebo.
Neuroimage
May 25, 2019
Louis-David Lord, Paul Expert, Selen Atasoy et al.
249 citations
Brain function can be understood as the exploration of a repertoire of metastable connectivity patterns that underlie different mental processes. Intravenous infusion of psilocybin rapidly modulates how the brain dynamically explores these resting-state networks. Using a data-driven approach focused on the leading eigenvector of BOLD phase coherence at single-TR resolution, recurrent BOLD phase-locking patterns were assessed pre- and post-infusion. A frontoparietal subsystem pattern was strongly destabilized after psilocybin, while a pattern characterized by global BOLD phase coherence became more probable. These results demonstrate network-specific neuromodulation by psilocybin, bridging molecular pharmacodynamics and whole-brain network dynamics.
Neuroscience & Biobehavioral Reviews
May 5, 2015
Federico Turkheimer, Robert Leech, Paul Expert et al.
64 citations
The brain appears to use repeated computational building blocks—canonical computational motifs—that are similar across species, brain areas, and sensory modalities. These motifs, grounded in stereotyped neuronal circuits and inhibitory interneurons, operate at micro-, meso-, and macro-scales to form a multiplexing information system capable of encoding and transmitting increasingly complex information. Similar activation patterns are observed in primary sensory cortices via electrophysiology and in large-scale networks measured with fMRI. The authors apply this canonical model to unify evidence on the pathophysiology of schizophrenia and suggest it may extend to other brain disorders involving GABA interneuron dysfunction.
bioRxiv (Cold Spring Harbor Laboratory)
July 25, 2018
Louis-David Lord, Paul Expert, Selen Atasoy et al.
10 citations
preprint
Brain activity can be viewed as exploring a landscape of different activity patterns over time, shifting between stable states of functional connectivity that support various mental processes. In a study using fMRI data from healthy participants given intravenous psilocybin (the active compound in magic mushrooms), researchers analyzed how this dynamical landscape changes during the psychedelic state. They found that a connectivity state linked to the fronto-parietal control system became strongly destabilized, while transitions toward a globally synchronized state increased. These changes suggest the psychedelic state biases the brain toward global integration at the cost of local network segregation, offering a mechanistic perspective on the subjective psychedelic experience and potential guidance for pharmacological interventions in neuropsychiatric disorders.
Frontiers in network physiology
January 1, 2023
Louis-David Lord, Timoteo Carletti, Henrique Fernandes et al.
Normal waking consciousness requires a balance between global integration (long-distance brain interactions) and segregation (local processing). Altered states, such as anesthesia, tip this balance. Using electrocorticography (ECoG) in a monkey under ketamine or propofol anesthesia, the study examined band-specific synchronization across the whole brain and within localized clusters. Both anesthetics caused a loss of long-range integration in multiple frequency bands, most pronounced in beta (13-30 Hz) and low-gamma (30-80 Hz) bands, while local synchrony was strongly preserved in all bands. This demonstrates a shift away from the integration/segregation equilibrium at sub-second time scales.