Collapse of local circuit integrated information {Phi} during NREM sleep

Clarifying the mechanisms underlying the emergence of consciousness remains a fundamental challenge in modern neuroscience. Integrated Information Theory (IIT) provides a mathematical framework derived from the phenomenological properties of consciousness as its axioms. IIT proposes that consciousness is identical to a systems intrinsic cause-effect information structure, quantified by integrated information {Phi}. While IIT predicts that the {Phi} of a neuronal system should decrease during the loss of consciousness, this hypothesis has remained untested at the neural circuit level. The present study provides empirical support for this IIT prediction. It was found that {Phi} within local circuits decreases during non-rapid-eye-movement (NREM) sleep compared to wakefulness and REM sleep, independent of cortical laminar structure or firing rates or regions. The reduction in {Phi} was particularly pronounced during off-periods, when neural activity is collectively suppressed. These results imply that consciousness is an information structure that cannot be reduced to the properties of individual system elements (such as firing rates), and that its collapse is fundamentally linked to the loss of consciousness. The findings provide critical empirical support for IIT as a mathematical theory aiming to explain conscious experiences. Significance StatementThis study bridges the gap between abstract mathematical theories of consciousness and high-resolution neurophysiology. According to Integrated Information Theory (IIT), conscious existence depends on a systems intrinsic cause-effect structure. By analyzing neural population activity, this study demonstrates that the transition from wakefulness to NREM sleep is characterized by a reduction in integrated information ({Phi}) within local circuits. This reduction is most pronounced during NREM off-periods, where causal integration is effectively severed, leading to a breakdown of the systems intrinsic information structure. These findings provide a neural foundation for IIT and suggest that consciousness is underpinned by specific, irreducible cause-effect structures within the brain.