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Somatosensory attention identifies both overt and covert awareness in disorders of consciousness
Author(s) -
Gibson Raechelle M.,
Chennu Srivas,
FernándezEspejo Davinia,
Naci Lorina,
Owen Adrian M.,
Cruse Damian
Publication year - 2016
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.24726
Subject(s) - p3a , p3b , covert , psychology , neuroimaging , persistent vegetative state , cognition , functional magnetic resonance imaging , event related potential , electroencephalography , neuroscience , cognitive psychology , functional neuroimaging , minimally conscious state , somatosensory system , consciousness , linguistics , philosophy
Objective 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. Methods 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. Results 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. Interpretation 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