Sackler Centre for Consciousness Science

Neural correlates of the psychedelic state

We are analysing state-of-the-art new magnetoencephalography (MEG) recordings from subjects in a psychedelic state from being administered the psychoactive substances LSD, ketamine and psilocybin. A key finding is that of increased neural dynamical complexity in the psychedelic state, as measured by the Lempel-Ziv index. The complexity index captures the degree of randomness and diversity of patterns in the data and correlates with the more “fluid” phenomenology experienced in the psychedelic state. The finding is interesting because it is the first demonstration that there exists a brain state with higher complexity than the wakeful resting state. In parallel research (see Theory and Modelling) we are studying in detail the decreases in complexity observed during anaesthesia and non-rapid eye movement sleep.

We are also analysing functional connectivity, including Granger causality on these data, and exploring the correlation of multiple neural dynamical features with individual reports of altered experience. In this way we aim to further enhance our understanding of the neurophysiological, cognitive and experiential changes underlying the psychedelic state. There is potential clinical application as psychoactive substances are currently being trialled as treatment for depression and anxiety.

People:

Michael Schartner, Adam Barrett, Lionel Barnett, Anil Seth (in collaboration with Robin Carhart-Harris, Imperial College London and Suresh Muthukumaraswamy, University of Auckland, New Zealand)