Perturbational Complexity Index

Perturbational Complexity Index (PCI) is a quantitative measure used in neuroscience to assess the level of consciousness based on the complexity of brain responses to external perturbations, typically induced via transcranial magnetic stimulation (TMS). It was introduced in 2013 by Italian M.D.–Ph.D. Marcello Massimini and colleagues as a practical application of principles from Integrated Information Theory (IIT), which posits that conscious systems must exhibit both high integration and differentiation of information.^[1]