Increased Entropic Brain Dynamics during DeepDream-Induced Altered Perceptual Phenomenology

Introduction

Greco and colleagues situate this study within a resurgence of neuroscientific interest in psychedelic substances (for example LSD, psilocybin, ketamine) as tools to probe the neural dynamics of conscious perception. Earlier empirical work has reported increased signal entropy, a larger repertoire of dynamical brain states and altered functional connectivity during pharmacologically induced psychedelic states. Those findings underpin the entropic brain hypothesis, which characterises psychedelic altered consciousness as a higher-entropy regime of brain activity. However, the authors note practical and ethical impediments to pharmacological studies—legal restrictions and difficulty separating direct neural effects from systemic physiological consequences of the drugs. To address these obstacles, the investigators adapted a non-pharmacological method to simulate hallucination-like visual input using the DeepDream algorithm, building on prior behavioural work (the Hallucination Machine). The study set out to test whether DeepDream-modified videos elicit EEG signatures akin to those reported for psychedelic states. Specifically, Greco sought to compare entropy and statistical complexity of EEG time series across multiple time scales, and to examine entropy-related measures of functional connectivity networks, contrasting responses to a regular video (OR) and its DeepDream-modified counterpart (DD). This is presented as the first neurophysiological investigation of artificially induced altered perceptual phenomenology using this approach.