Identifying Covert Cognition in Disorders of Consciousness

Several recent studies examining different aspects of residual cognitive function in patients with disorders of consciousness (DOC) have shown that multiple tasks and modalities provide the best opportunity for patients to demonstrate covert awareness where it exists. With a wide range of etiologies and comorbidities, this is a very diverse population with variable cognitive and behavioral abilities. Additional challenges include the availability of specific technology as well as the eligibility of individual patients to be assessed with functional magnetic resonance imaging (fMRI) or electroencephalography (EEG). A number of paradigms, in different modalities, have been developed in recent years to assess aspects of residual cognitive function in DOC patients. These include basic auditory, visual, and tactile processing, speech-specific processes, selective attention, executive function, and command following. The results confirm that preserved brain function in DOC may take a wide variety of forms, from basic auditory processing all the way up to preserved command following and communication.