Subjective experience is multifaceted, making consciousness hard to study because traditional theories often focus on isolated aspects like perception or wakefulness and are difficult to compare. This work starts from active inference—a first-principles framework that models behavior as approximate Bayesian inference—and builds toward a minimal theory of consciousness derived from shared features of computational models under active inference. Reviewing models applied to consciousness, the authors argue that these models imply a small set of theoretical commitments pointing to a minimal, testable theory of consciousness.
Ketamine rapidly reduces depressive symptoms in treatment-resistant major depressive disorder. Using brain imaging and dynamic causal modeling, researchers analyzed neural excitation/inhibition interactions in the primary somatosensory cortex of 18 unmedicated patients and 18 healthy controls during a somatosensory task. Patients were scanned at baseline, 6-9 hours after ketamine infusion, and 6-9 hours after placebo. A shift in neural dynamics toward a stable region of the Poincaré diagram—requiring increased excitatory and inhibitory coupling—predicted symptom improvement specifically after ketamine, not placebo. This drug-specific neural shift may serve as a biomarker for treatment response.