Assessing the level of consciousness in severely injured patients is a difficult task both technically and emotionally. A person might be locked-in and incapable of communicating in any way while the brain is aware of what’s going on around. A team of researchers in Europe have developed a promising way of using transcranial magnetic stimulation (TMS) to assess consciousness and tested it on healthy subjects as well as those that emerged from vegetative state, minimally conscious state, and locked-in syndrome.
The system calculates a perturbational complexity index (PCI) by directing a magnetic field at the cortex to activate large regions of the brain and then narrowing the field’s focus to measure the “algorithmic complexity” of electrocortical responses.
From the study abstract in Science Translational Medicine:
We test PCI on a large data set of TMS-evoked potentials recorded in healthy subjects during wakefulness, dreaming, nonrapid eye movement sleep, and different levels of sedation induced by anesthetic agents (midazolam, xenon, and propofol), as well as in patients who had emerged from coma (vegetative state, minimally conscious state, and locked-in syndrome). PCI reliably discriminated the level of consciousness in single individuals during wakefulness, sleep, and anesthesia, as well as in patients who had emerged from coma and recovered a minimal level of consciousness. PCI can potentially be used for objective determination of the level of consciousness at the bedside.
Science Translational Medicine: A Theoretically Based Index of Consciousness Independent of Sensory Processing and Behavior
(hat tip: Wired)