Functional near infrared spectroscopy as a probe of brain function in people with prolonged disorders of consciousness

Near infrared spectroscopy (NIRS) is a non-invasive technique which measures changes in brain tissue oxygenation. NIRS has been used for continuous monitoring of brain oxygenation during medical procedures carrying high risk of iatrogenic brain ischemia and also has been adopted by cognitive neuroscience for studies on executive and cognitive functions. Until now, NIRS has not been used to detect residual cognitive functions in patients with prolonged disorders of consciousness (pDOC). In this study we aimed to evaluate the brain function of patients with pDOC by using a motor imagery taskwhile recording NIRS. We also collected data from a group of age and gendermatched healthy controls while they carried out both real and imaginedmotor movements to command. We studied 16 pDOC patients in total, split into two groups: five had a diagnosis of Vegetative state/ Unresponsive Wakefulness State, and eleven had a diagnosis ofMinimally Conscious State. In the control subjects we found a greater oxy-haemoglobin (oxyHb) response during realmovement comparedwith imaginedmovement. For the between group comparison, we found amain effect of hemisphere, with greater depression of oxyHb signal in the right N left hemisphere compared with rest period for all three groups. A post-hoc analysis including only the two pDOC patient groups was also significant suggesting that this effect was not just being driven by the control subjects. This study demonstrates for the first time the feasibility of using NIRS for the assessment of brain function in pDOC patients using a motor imagery task. Crown Copyright (C) 2016 Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license