Neural Correlates of Psychedelic, Sleep, and Sedated States Support Global Theories of Consciousness.

Consciousness appears to depend on global interactions across multiple brain regions rather than on localized neural activity. Using fMRI data across psychedelic, sleep, and deep sedation states, the study found a mirror-image pattern: psychedelic states increased global functional connectivity and decreased local neural synchrony, while non-REM sleep and deep sedation showed the opposite pattern. This pattern was observed in anterior-posterior and posterior-posterior brain regions but not within the anterior brain alone. Anterior transmodal regions were key for anterior-posterior connectivity, while posterior transmodal and unimodal regions were critical for posterior-posterior connectivity. The findings support global theories of consciousness and bridge the Global Neuronal Workspace hypothesis and Integrated Information Theory by showing shared neural mechanisms.

Study at a glance

Abstract

Understanding neural mechanisms of consciousness remains a challenging question in neuroscience. A central debate in the field concerns whether consciousness arises from global interactions that involve multiple brain regions or focal neural activity, such as in sensory cortex. Additionally, global theories diverge between the Global Neuronal Workspace (GNW) hypothesis, which emphasizes frontal and parietal areas, and the Integrated Information Theory (IIT), which focuses on information integration within posterior cortical regions. To disentangle the global vs. local and frontoparietal vs. posterior dilemmas, we measured global functional connectivity and local neural synchrony with functional magnetic resonance imaging (fMRI) data across a spectrum of conscious states in humans induced by psychedelics, sleep, and deep sedation. We found that psychedelic states are associated with increased global functional connectivity and decreased local neural synchrony. In contrast, non-REM sleep and deep sedation displayed the opposite pattern, suggesting that consciousness arises from global brain network interactions rather than localized activity. This mirror-image pattern between enhanced and diminished states was observed in both anterior-posterior (A-P) and posterior-posterior (P-P) brain regions but not within the anterior part of the brain alone. Moreover, anterior transmodal regions played a key role in A-P connectivity, while both posterior transmodal and posterior unimodal regions were critical for P-P connectivity. Overall, these findings provide empirical evidence supporting global theories of consciousness in relation to varying states of consciousness. They also bridge the gap between two prominent theories, GNW and IIT, by demonstrating how different theories can converge on shared neuronal mechanisms.