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dc.contributor.authorVarley, Thomas F
dc.contributor.authorCarhart-Harris, Robin
dc.contributor.authorRoseman, Leor
dc.contributor.authorMenon, David K
dc.contributor.authorStamatakis, Emmanuel A
dc.date.accessioned2020-06-22T23:32:05Z
dc.date.available2020-06-22T23:32:05Z
dc.date.issued2020-10-15
dc.identifier.issn1053-8119
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/307122
dc.description.abstractPsychedelic drugs, such as psilocybin and LSD, represent unique tools for researchers investigating the neural origins of consciousness. Currently, the most compelling theories of how psychedelics exert their effects is by increasing the complexity of brain activity and moving the system towards a critical point between order and disorder, creating more dynamic and complex patterns of neural activity. While the concept of criticality is of central importance to this theory, few of the published studies on psychedelics investigate it directly, testing instead related measures such as algorithmic complexity or Shannon entropy. We propose using the fractal dimension of functional activity in the brain as a measure of complexity since findings from physics suggest that as a system organizes towards criticality, it tends to take on a fractal structure. We tested two different measures of fractal dimension, one spatial and one temporal, using fMRI data from volunteers under the influence of both LSD and psilocybin. The first was the fractal dimension of cortical functional connectivity networks and the second was the fractal dimension of BOLD time-series. In addition to the fractal measures, we used a well-established, non-fractal measure of signal complexity and show that they behave similarly. We were able to show that both psychedelic drugs significantly increased the fractal dimension of functional connectivity networks, and that LSD significantly increased the fractal dimension of BOLD signals, with psilocybin showing a non-significant trend in the same direction. With both LSD and psilocybin, we were able to localize changes in the fractal dimension of BOLD signals to brain areas assigned to the dorsal-attenion network. These results show that psychedelic drugs increase the fractal dimension of activity in the brain and we see this as an indicator that the changes in consciousness triggered by psychedelics are associated with evolution towards a critical zone.
dc.description.sponsorshipNIHR Wellcome NSF-NRT MRC Beckley Foundation Alex Mosley Charitable Trust Ad Astria Chandaria Foundation. Neuro-psychoanalysis Foundation Multidisplinary Association for Psychedelic Studies The Heffter Research Institute
dc.format.mediumPrint-Electronic
dc.languageeng
dc.publisherElsevier BV
dc.rightsAttribution-NonCommercial-NoDerivatives 4.0 International
dc.rights.urihttps://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subjectCerebral Cortex
dc.subjectHumans
dc.subjectLysergic Acid Diethylamide
dc.subjectHallucinogens
dc.subjectMagnetic Resonance Imaging
dc.subjectConsciousness
dc.subjectPsilocybin
dc.subjectDefault Mode Network
dc.titleSerotonergic psychedelics LSD & psilocybin increase the fractal dimension of cortical brain activity in spatial and temporal domains.
dc.typeArticle
prism.publicationDate2020
prism.publicationNameNeuroimage
prism.startingPage117049
prism.volume220
dc.identifier.doi10.17863/CAM.54215
dcterms.dateAccepted2020-06-09
rioxxterms.versionofrecord10.1016/j.neuroimage.2020.117049
rioxxterms.versionAM
rioxxterms.licenseref.urihttp://www.rioxx.net/licenses/all-rights-reserved
rioxxterms.licenseref.startdate2020-10
dc.contributor.orcidStamatakis, Emmanuel [0000-0001-6955-9601]
dc.identifier.eissn1095-9572
rioxxterms.typeJournal Article/Review
cam.issuedOnline2020-06-30
cam.orpheus.successTue Feb 01 18:59:45 GMT 2022 - Embargo updated
cam.orpheus.counter4
rioxxterms.freetoread.startdate2020-10-31


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Attribution-NonCommercial-NoDerivatives 4.0 International
Except where otherwise noted, this item's licence is described as Attribution-NonCommercial-NoDerivatives 4.0 International