A new study, published in the journal Science Translational Medicine, considered the challenge of measuring consciousness in unresponsive patients with brain injuries.  Currently, clinical assessment is based on the subject’s ability to interact with the external environment, but there are levels of consciousness that may exist even when the patient cannot interact.  The researchers examine a measure called the perturbational complexity index (PCI), which is based on the theory that consciousness comes from the brain being able to support complex activity patterns across cortical areas and differentiated in space and time.

PCI is measured using transcranial magnetic stimulation (TMS) and by collecting and analyzing brain data.  The researchers used TMS to measure PCI in healthy subjects during various states of consciousness, including wakefulness, dream, nonrapid eye movement sleep, and different levels of sedation.  They also tested patients that had emerged from a coma.  The researchers concluded that this method provided reliable discernment between the tested levels of consciousness.

The different states of consciousness for participants in a coma can affect what treatment they should be offered.  Wired Magazine reports that a vegetative state is one where the patient is awake, but completely unconscious.  On the PCI scale, the vegetative state scores very low.  The locked-in syndrome is considered a comatose state in which the cognitive abilities are normal, but the person is unable to move.  They can only communicate by moving their eyes.  These individuals scored just as high on the PCI scale as waking, healthy patients.  Of those that emerged from the coma, there were varying scores on the PCI scale.

In an analysis of the new study, Bloomberg summarizes this technique as using a strong magnetic stimulation to shake the entire brain.  Given the success of the study, the analysis concludes that this technique would be particularly useful for patients in intensive care, where there are currently no objective measures for consciousness, resulting in a greater number of incorrect diagnoses.

Bloomberg also lists the TMS devices currently available.  The device used for this study produces the stimulation and simultaneously records electrical responses.  Another TMS device is available on the market, but it is currently used for treating depression and other neurological conditions.

TMS is currently used to treat depression, reports the Mayo Clinic.  A large electromagnetic coil is placed against the scalp near the forehead.  The electromagnet is used to create electric currents directed at the area of the brain involved in mood control.  This is a relatively new treatment for depression, which still needs studies to confirm its effectiveness and best practices.