Bridging the Gap Towards Awareness Detection in Disorders of Consciousness: An Experimental Study on the Mirror Neuron System

Advanced functional neuroimaging approaches dealing with motor imagery have disclosed covert cognitive processes in patients with disorders of consciousness (DoC). However, motor impairment and cognitive-motor dissociation can bias such approaches. Fourteen patients with post-traumatic DoC and ten healthy controls (HC) were provided with three motor tasks related to mirror neuron system (MNS) activation (movement observation, movement execution, and passive motor imagery of a movement) while recording electroencephalographic (EEG) metrics [EEG power and Granger Casualty Index (GCI)] to detect residual signs of conscious awareness. The most relevant finding was that all HCs, all patients with Minimally Conscious State and one with Unresponsive Wakefulness Syndrome demonstrated an event-related synchronization in the gamma range over left frontal regions, with high GCI values, in the passive motor imagery condition. These data significantly correlated with the level of behavioral responsiveness measured by the Coma Recovery Scale-Revised. Thus, our findings may indicate that motor tasks related to MNS can activate frontoparietal networks, although leading to different conscious processes. Hence, MNS assessment can be usefully employed to differentiate among patients with DoC.