title: Somatosensory attention identifies both overt and covert awareness in disorders of consciousness.
abstract: Some patients diagnosed with disorders of consciousness retain sensory and cognitive abilities beyond those apparent from their overt behavior. Characterizing these covert abilities is crucial for diagnosis, prognosis, and medical ethics. This multimodal study investigates the relationship between electroencephalographic evidence for perceptual/cognitive preservation and both overt and covert markers of awareness.
  
  
  
  Fourteen patients with severe brain injuries were evaluated with an electroencephalographic vibrotactile attention task designed to identify a hierarchy of residual somatosensory and cognitive abilities: (1) somatosensory steady-state evoked responses, (2) bottom-up attention orienting (P3a event-related potential), and (3) top-down attention (P3b event-related potential). Each patient was also assessed with a clinical behavioral scale and 2 functional magnetic resonance imaging assessments of covert command following.
  
  
  
  Six patients produced only sensory responses, with no evidence of cognitive event-related potentials. A further 8 patients demonstrated reliable bottom-up attention-orienting responses (P3a). No patient showed evidence of top-down attention (P3b). Only those patients who followed commands, whether overtly with behavior or covertly with functional neuroimaging, also demonstrated event-related potential evidence of attentional orienting.
  
  
  
  Somatosensory attention-orienting event-related potentials differentiated patients who could follow commands from those who could not. Crucially, this differentiation was irrespective of whether command following was evident through overt external behavior, or through covert functional neuroimaging methods. Bedside electroencephalographic methods may corroborate more expensive and challenging methods such as functional neuroimaging, and thereby assist in the accurate diagnosis of awareness. Ann Neurol 2016;80:412-423.
authors.affiliation: Department of Psychology, University of Western Ontario, London, Ontario, Canada. rgibso5@uwo.ca.|Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada. rgibso5@uwo.ca.
authors.forename: Raechelle M
authors.identifier: 0000-0002-6690-5078
authors.initials: RM
authors.lastname: Gibson
authors.affiliation: School of Computing, University of Kent, Chatham Maritime, United Kingdom.|Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Srivas
authors.initials: S
authors.lastname: Chennu
authors.affiliation: School of Psychology, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Davinia
authors.identifier: 0000-0001-5941-7546
authors.initials: D
authors.lastname: Fernández-Espejo
authors.affiliation: Department of Psychology, University of Western Ontario, London, Ontario, Canada.|Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada.
authors.forename: Lorina
authors.initials: L
authors.lastname: Naci
authors.affiliation: Department of Psychology, University of Western Ontario, London, Ontario, Canada.|Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada.
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Owen
authors.affiliation: School of Psychology, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Damian
authors.initials: D
authors.lastname: Cruse
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D001364:Awareness / Q000502:physiology*; D001930:Brain Injuries / Q000150:complications; D003244:Consciousness Disorders / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D004569:Electroencephalography; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D055815:Young Adult