title: Mismatch negativity abnormality in traumatic brain injury without macroscopic lesions on conventional MRI.
abstract: Traumatic brain injury (TBI) causes damage through complex pathophysiological mechanisms. Deficits related to traumatic axonal injury persist in a subset of patients with no macroscopic lesions on conventional MRI. We examined two event-related brain potentials, mismatch negativity (MMN) and P3a, to identify possible electrophysiological anomalies in this subset of TBI patients in comparison with TBI patients with focal abnormalities on MRI/computed tomography and healthy controls. Each group consisted of 10 individuals. A passive oddball paradigm, in which the individuals were instructed to ignore auditory stimuli while watching a silent movie, consisted of non-native speech sounds presented in a random order. Patients with no discernible lesions on conventional MRI showed a significantly augmented amplitude of the brain's involuntary change-detection response MMN, relative to that of the two other groups. In patients with focal neuroradiological abnormalities, this MMN anomaly was not found, whereas the subsequent orientation-related P3a response was significantly enlarged when compared with that of the controls. The present findings demonstrate that MMN is indicative of a functional abnormality in the mechanisms of involuntary attention in chronic TBI patients with normal conventional MRI findings, indexing their increased distractibility associated with the traumatically-induced loss of neural integrity.
authors.affiliation: Cognitive Brain Research Unit, Institute of Behavioral Sciences, University of Helsinki, Helsinki, Finland. marja-liisa.kaipio@helsinki.fi
authors.forename: Marja-Liisa
authors.initials: ML
authors.lastname: Kaipio
authors.forename: Marie
authors.initials: M
authors.lastname: Cheour
authors.forename: Juha
authors.initials: J
authors.lastname: Ohman
authors.forename: Oili
authors.initials: O
authors.lastname: Salonen
authors.forename: Risto
authors.initials: R
authors.lastname: Näätänen
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D001288:Attention / Q000502:physiology; D001930:Brain Injuries / Q000503:physiopathology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D011930:Reaction Time / Q000502:physiology; D055815:Young Adult