posted on 2024-01-12, 15:34authored byPedro A. M. Mediano, Fernando E. Rosas, Christopher Timmermann, Leor Roseman, David J. Nutt, Amanda Feilding, Mendel Kaelen, Morten L. Kringelbach, Adam B. Barrett, Anil K. Seth, Suresh Muthukumaraswamy, Daniel Bor, Robin L. Carhart-Harris
Recent findings have
shown that psychedelics reliably enhance brain
entropy (understood as neural signal diversity), and this effect has
been associated with both acute and long-term psychological outcomes,
such as personality changes. These findings are particularly intriguing,
given that a decrease of brain entropy is a robust indicator of loss
of consciousness (e.g., from wakefulness to sleep). However, little
is known about how context impacts the entropy-enhancing effect of
psychedelics, which carries important implications for how it can
be exploited in, for example, psychedelic psychotherapy. This article
investigates how brain entropy is modulated by stimulus manipulation
during a psychedelic experience by studying participants under the
effects of lysergic acid diethylamide (LSD) or placebo, either with
gross state changes (eyes closed vs open) or different stimuli (no
stimulus vs music vs video). Results show that while brain entropy
increases with LSD under all of the experimental conditions, it exhibits
the largest changes when subjects have their eyes closed. Furthermore,
brain entropy changes are consistently associated with subjective
ratings of the psychedelic experience, but this relationship is disrupted
when participants are viewing a videopotentially due to a
“competition” between external stimuli and endogenous
LSD-induced imagery. Taken together, our findings provide strong quantitative
evidence of the role of context in modulating neural dynamics during
a psychedelic experience, underlining the importance of performing
psychedelic psychotherapy in a suitable environment.