Marcello Massimini
University of Milan
Integrated information Consciousness is intrinsic causal power, measured as integrated information
Marcello Massimini is a neurophysiologist at the University of Milan whose laboratory produced the field’s most validated consciousness measurement. The Perturbational Complexity Index (PCI), introduced by Silvia Casali and colleagues in 2013, perturbs the cortex with transcranial magnetic stimulation and scores the spatiotemporal complexity of the EEG response. The index requires no sensory input, no behavioral report, and no cooperation from the subject, which is what makes it decisive for the patients it was built for. Examined on this site in the PCI measurement lineage analysis, PCI separates conscious from unconscious states across sleep, anesthesia, and severe brain injury from a single threshold.
The program’s depth is in its validation chain. The 2016 Annals of Neurology study by Silvia Casarotto and colleagues stratified behaviorally unresponsive patients by PCI and matched the stratification against covert command-following evidence, giving unresponsive patients with covert consciousness a measurable signal. Mechanism work traced low scores to sleep-like cortical OFF-periods that break causal integration, and by 2024 the index had entered a randomized controlled trial as a biomarker for treatment response, moving consciousness measurement from diagnosis into therapy.
Massimini’s earlier work on sleep slow waves set the stage, and the program’s theoretical stance, grounded in integrated-information-style complexity rather than in any single theory, keeps the instrument usable across theory disputes. For the AI consciousness debate, the Massimini lineage is the standard of evidence the site’s indicator posts invoke, a proposal that became a measurement, survived validation, and now closes a clinical feedback loop.
Known for. The Perturbational Complexity Index, TMS-EEG measurement of consciousness, disorders of consciousness assessment, sleep slow waves
Coverage on this site
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Marcello Massimini is listed with the other integrated information theorists, who hold that consciousness is intrinsic causal power, measured as integrated information. The theory family behind that position is set out in the index of consciousness theories. Every researcher covered on this site is indexed in the directory of consciousness researchers.