The Entropic Brain Hypothesis proposes that conscious states correspond to the entropy (diversity and unpredictability) of spontaneous brain activity. A recent cross-condition fMRI study found an entropic gradient: propofol anaesthesia reduced entropy, while LSD, DMT, modafinil, and schizophrenia increased it, with schizophrenia showing the largest increase. The present project aims to test this hypothesis more broadly by examining fMRI datasets from LSD, psilocybin, modafinil, propofol anaesthesia, natural sleep, schizophrenia, Mild Cognitive Impairment, Alzheimer's disease, and Frontotemporal Dementia. It hypothesizes that diminished states (sleep, anaesthesia) will show low entropy, psychedelic and stimulant states high entropy, and neurodegenerative conditions low entropy. A second objective is to compare a topology-derived entropy measure with a brain-state-derived Shannon entropy measure to assess robustness across operationalizations.
Brain waves coordinate neural communication and shape conscious perception. Analyzing blood oxygen level-dependent activity from the Human Connectome Project and other datasets across sleep, propofol anesthesia, and psychedelic states (LSD, DMT, psilocybin, nitrous oxide, ketamine), four dominant wave propagation motifs were identified: a global synchronized wave, an anti-correlated unimodal-transmodal wave, an anti-correlated task-positive/task-negative wave, and an anti-correlated visual-somatomotor wave.
An fMRI dataset from 26 healthy volunteers performing mental imagery tasks (tennis, navigation, hand squeeze) and a motor response task under graded propofol sedation captures brain activity across varying sedation levels, including instances of volitional mental imagery despite behavioral unresponsiveness. Prior analyses using this dataset have investigated the anterior insula's role in conscious access and asymmetric neural dynamics during loss and recovery of consciousness. The dataset provides a resource for exploring neural mechanisms of anesthesia and consciousness, featuring mental imagery tasks traditionally used only in disorders of consciousness.