CONCEPT
Perturbational Complexity Index
The Perturbational Complexity Index (PCI) is a clinical tool developed by Giulio Tononi in collaboration with Marcello Massimini at the University of Milan. It operationalizes IIT's prediction that consciousness manifests as complex, irreducible causal dynamics. A magnetic pulse is delivered to the cortex via transcranial magnetic stimulation, and the brain's electrical response is recorded using high-density EEG. The complexity and integration of the response — how broadly the perturbation propagates and how differentiated the resulting pattern — are quantified into a single number. The PCI distinguishes conscious from unconscious states across sleep, anesthesia, and disorders of consciousness with remarkable accuracy, often detecting awareness in patients where behavioral assessment fails.
In The You On AI Field Guide
The PCI addresses one of the oldest problems in clinical neurology: how to determine whether an unresponsive patient is conscious. Studies in the early 2000s found that approximately forty percent of patients diagnosed as vegetative were misdiagnosed — they were conscious but unable to demonstrate it through