title: The neural basis of impaired self-awareness after traumatic brain injury.
abstract: Self-awareness is commonly impaired after traumatic brain injury. This is an important clinical issue as awareness affects long-term outcome and limits attempts at rehabilitation. It can be investigated by studying how patients respond to their errors and monitor their performance on tasks. As awareness is thought to be an emergent property of network activity, we tested the hypothesis that impaired self-awareness is associated with abnormal brain network function. We investigated a group of subjects with traumatic brain injury (n = 63) split into low and high performance-monitoring groups based on their ability to recognize and correct their own errors. Brain network function was assessed using resting-state and event-related functional magnetic resonance imaging. This allowed us to investigate baseline network function, as well as the evoked response of networks to specific events including errors. The low performance-monitoring group underestimated their disability and showed broad attentional deficits. Neural activity within what has been termed the fronto-parietal control network was abnormal in patients with impaired self-awareness. The dorsal anterior cingulate cortex is a key part of this network that is involved in performance-monitoring. This region showed reduced functional connectivity to the rest of the fronto-parietal control network at 'rest'. In addition, the anterior insulae, which are normally tightly linked to the dorsal anterior cingulate cortex, showed increased activity following errors in the impaired group. Interestingly, the traumatic brain injury patient group with normal performance-monitoring showed abnormally high activation of the right middle frontal gyrus, putamen and caudate in response to errors. The impairment of self-awareness was not explained either by the location of focal brain injury, or the amount of traumatic axonal injury as demonstrated by diffusion tensor imaging. The results suggest that impairments of self-awareness after traumatic brain injury result from breakdown of functional interactions between nodes within the fronto-parietal control network.
authors.affiliation: 1 C3NL, Centre for Restorative Neuroscience, Division of Brain Sciences, Department of Medicine, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK.
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Ham
authors.forename: Valerie
authors.initials: V
authors.lastname: Bonnelle
authors.forename: Peter
authors.initials: P
authors.lastname: Hellyer
authors.forename: Sagar
authors.initials: S
authors.lastname: Jilka
authors.forename: Ian H
authors.initials: IH
authors.lastname: Robertson
authors.forename: Robert
authors.initials: R
authors.lastname: Leech
authors.forename: David J
authors.initials: DJ
authors.lastname: Sharp
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001364:Awareness / Q000502:physiology*; D001921:Brain / Q000473:pathology / Q000503:physiopathology*; D001930:Brain Injuries / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000473:pathology / Q000502:physiology / Q000503:physiopathology*; D009474:Neurons / Q000473:pathology; D011597:Psychomotor Performance / Q000502:physiology*; D055815:Young Adult
keywords: fronto-parietal control network; functional connectivity; salience network; self-awareness; traumatic brain injury