Marcello Massimini

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

• Berjaga-Buisan and Kringelbach Track Consciousness Through a Thermodynamic Violation September 2026
• The Perturbational Complexity Index Measures Consciousness From the Brain's Response September 2026

Related researchers

• TB Tomas Berjaga-BuisanComputational Neuroscience Group, Center for Brain and Cognition, Universitat Pompeu Fabra, BarcelonaNon-equilibrium thermodynamics of whole-brain models, fluctuation-dissipation theorem violations as a non-invasive consciousness marker Biological naturalist1 article
• MK Morten KringelbachDepartment of Psychiatry, University of Oxford; Centre for Eudaimonia and Human Flourishing, Linacre College, Oxford; Department of Clinical Medicine, Aarhus UniversityWhole-brain computational modeling of non-equilibrium brain dynamics, the thermodynamics of mind framework, hedonic and pleasure circuitry Biological naturalist2 articles
• Gustavo DecoICREA, Universitat Pompeu Fabra, BarcelonaWhole-brain computational models, metastability at the edge of the Hopf bifurcation, the dynamical cortical core Functionalist1 article
• LA Larissa AlbantakisUniversity of Wisconsin-Madison, Center for Sleep and ConsciousnessIntegrated Information Theory 4.0 and dissociating intelligence from consciousness in artificial systems Integrated information2 articles
• CA Costas AnastassiouAllen InstituteEphaptic coupling of cortical neurons, endogenous electric fields as causal participants in neural activity, extracellular field biophysics Integrated information1 article
• AA Anton ArkhipovAllen Institute for Brain ScienceLarge-scale neural simulation, biophysically detailed cortical models, AIBRAIN program, State of Brain Emulation Report 2025 Integrated information1 article

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.