Neuroentropy and Consciousness: A Meta-Analytic Review

Abstract

Neuroentropy (understood as the complexity or diversity of brain activity) has emerged as a possible quantitative marker of consciousness. This meta-analytic review synthesizes evidence from EEG, MEG, fMRI, intracranial recordings, and perturbation-based approaches (e.g., Perturbational Complexity Index) across 2013–2023. Findings show higher entropy during wakefulness, REM sleep, and psychedelic states, and reduced entropy in anesthesia, deep NREM sleep, and disorders of consciousness. Psychedelic states pharmacologically elevate entropy, correlating with vivid, diverse phenomenology, while unconscious states exhibit low-complexity dynamics. Entropy measures have demonstrated clinical value, particularly in anesthesia monitoring and detecting covert awareness. It is important to note that challenges remain regarding metric selection, distinguishing meaningful complexity from noise, and mapping entropy to consciousness content. Overall, the concept of neuroentropy can be understood as a powerful, physiologically grounded index for consciousness level and its possible alterations.