S-126 | Entropy of the brain as a biomarker for the study of Altered States of Consciousness under the effect of LSD using fMRI

Theoretical and Computational Neuroscience
Author: Dante Sebastian Galvan Rial | Email: sebas.galvan@mi.unc.edu.ar

Dante Sebastián Galván Rial^1°4°, Gabriel Della Bella^1°2°, Tristan Martin Osan^4°,  Emmanuel A. Stamatakis^3°, Pablo Barttfeld^1°

^1° Cognitve Science Group, Instituto de Investigaciones Psicologicas, Universidad Nacional de Cordoba
^2° Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba
^3° Cognition and Consciousness Imaging Group, Division of Anaesthesia, University of Cambridge
^4° Instituto de Física Dr. Enrique Gaviola, UNC

The revival of scientific interest in psychedelics has prompted research into the neural correlates of their effects. Entropy is a unitless measure often used to quantify the uncertainty of a system’s state, but it can also reflect physical properties, where greater entropy indicates greater disorder. This study analyses subjects who consumed LSD vs. a placebo, applying sampling entropy and Graph Theory small-world measures.
Data, obtained and preprocessed by Carhart-Harris (2016), were parsed using 2 anatomical atlases (AAL and AICHA ) and a functional atlas (Power300). The time series were windowed to construct thresholded and undirected connectivity matrices. Regions of interest correspond to nodes and Pearson correlations between nodes to weighted edges. In addition, inter- and intra-network connectivity was explored in 13 functional networks.
Linear mixed effects statistics showed that sampling entropy was higher in LSD than in Placebo in AAL (β = 0.071, p = 0.002) and AICHA (β = 0.13, p = 0.001). The Power300 atlas highlighted significance in the Visual, Fronto-Parietal and Dorsal Sensorimotor networks. Inter-network connectivity increased in 7 of 13 networks (p < 0.05). These findings suggest that LSD induces significant brain reorganisation, increasing inter-network integration and synchronisation, specially in areas associated with altered states of consciousness, helping to understand the profound changes in perception and cognition experienced by subjects.