Altered states of consciousness, such as those experienced during dreaming or meditation, offer a way to study how large-scale brain activity relates to different subjective experiences. This paper advocates a research program that combines bottom-up generative models of whole-brain activity, based on known properties of neural tissue, with top-down signatures proposed by theories of consciousness. The authors define altered states, discuss relevant brain-activity signatures, and introduce whole-brain models to explore the mechanisms behind these states. They argue that systematically investigating altered states through bottom-up modeling can clarify the biophysical, informational, and dynamical foundations of consciousness.
Integrated Information Theory (IIT) defines consciousness as a fundamental property of physical systems, measured by the quantity Phi. For IIT to be credible, Phi must be uniquely defined and always well-defined. This article identifies three ways in which the current formulation of Phi fails these standards, making the measure ambiguous or ill-defined in certain cases, and discusses potential solutions to address these foundational issues.