title: Filling in the gaps: Anticipatory control of eye movements in chronic mild traumatic brain injury.
abstract: A barrier in the diagnosis of mild traumatic brain injury (mTBI) stems from the lack of measures that are adequately sensitive in detecting mild head injuries. MRI and CT are typically negative in mTBI patients with persistent symptoms of post-concussive syndrome (PCS), and characteristic difficulties in sustaining attention often go undetected on neuropsychological testing, which can be insensitive to momentary lapses in concentration. Conversely, visual tracking strongly depends on sustained attention over time and is impaired in chronic mTBI patients, especially when tracking an occluded target. This finding suggests deficient internal anticipatory control in mTBI, the neural underpinnings of which are poorly understood. The present study investigated the neuronal bases for deficient anticipatory control during visual tracking in 25 chronic mTBI patients with persistent PCS symptoms and 25 healthy control subjects. The task was performed while undergoing magnetoencephalography (MEG), which allowed us to examine whether neural dysfunction associated with anticipatory control deficits was due to altered alpha, beta, and/or gamma activity. Neuropsychological examinations characterized cognition in both groups. During MEG recordings, subjects tracked a predictably moving target that was either continuously visible or randomly occluded (gap condition). MEG source-imaging analyses tested for group differences in alpha, beta, and gamma frequency bands. The results showed executive functioning, information processing speed, and verbal memory deficits in the mTBI group. Visual tracking was impaired in the mTBI group only in the gap condition. Patients showed greater error than controls before and during target occlusion, and were slower to resynchronize with the target when it reappeared. Impaired tracking concurred with abnormal beta activity, which was suppressed in the parietal cortex, especially the right hemisphere, and enhanced in left caudate and frontal-temporal areas. Regional beta-amplitude demonstrated high classification accuracy (92%) compared to eye-tracking (65%) and neuropsychological variables (80%). These findings show that deficient internal anticipatory control in mTBI is associated with altered beta activity, which is remarkably sensitive given the heterogeneity of injuries.
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, CA, USA.
authors.forename: Mithun
authors.initials: M
authors.lastname: Diwakar
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, CA, USA ; Radiology and Research Services, VA San Diego Healthcare System, San Diego, CA, USA.
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Harrington
authors.affiliation: Brain Trauma Foundation, New York, NY, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Maruta
authors.affiliation: Brain Trauma Foundation, New York, NY, USA ; Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Jamshid
authors.initials: J
authors.lastname: Ghajar
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, CA, USA.
authors.forename: Fady
authors.initials: F
authors.lastname: El-Gabalawy
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, CA, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Muzzatti
authors.affiliation: Department of Neurology, Washington University, St. Louis, MO, USA.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Corbetta
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, CA, USA ; Radiology and Research Services, VA San Diego Healthcare System, San Diego, CA, USA.
authors.forename: Ming-Xiong
authors.initials: MX
authors.lastname: Huang
authors.affiliation: Department of Radiology, University of California, San Diego, San Diego, CA, USA ; Radiology and Research Services, VA San Diego Healthcare System, San Diego, CA, USA.
authors.forename: Roland R
authors.initials: RR
authors.lastname: Lee
mesh_terms: D000328:Adult; D059031:Anticipation, Psychological / Q000502:physiology; D001611:Beta Rhythm / Q000502:physiology*; D020208:Brain Injury, Chronic / Q000503:physiopathology*; D002421:Caudate Nucleus / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology*; D053483:Eye Movement Measurements; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D038223:Post-Concussion Syndrome / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*
keywords: Anticipatory control; Attention; Magnetoencephalography; Mild traumatic brain injury; Visual tracking