title: Electrophysiology and functional MRI in post-acute mild traumatic brain injury.
abstract: Symptoms persisting beyond the acute phase (>2 months) after a mild traumatic brain injury (MTBI) are often reported, but their origin remains controversial. Some investigators evoke dysfunctional cerebral mechanisms, while others ascribe them to the psychological consequences of the injury. We address this controversy by exploring possible cerebral dysfunction with functional magnetic resonance imaging (fMRI) and event-related potentials (ERP) in a group of patients during the post-acute phase. Fourteen MTBI symptomatic patients (5.7±2.9 months post-injury) were tested with fMRI and ERP using a visual externally ordered working memory task, and were compared with 23 control subjects. Attenuated blood oxygen level dependent (BOLD) signal changes in the left and right mid-dorsolateral prefrontal cortex (mid-DLPFC), the putamen, the body of the caudate nucleus, and the right thalamus were found in the MTBI group compared with the control group. Moreover, symptom severity and BOLD signal changes were correlated: patients with more severe symptoms had lower BOLD signal changes in the right mid-DLPFC. For ERP, a group×task interaction was observed for N350 amplitude. A larger amplitude for the working memory task than for the control task was found in control subjects, but not in MTBI subjects, who had weak amplitudes for both tasks. This study confirms that persistent symptoms after MTBI cannot be uniquely explained by psychological factors, such as depression and/or malingering, and indicates that they can be associated with cerebral dysfunction. ERP reveals decreased amplitude of the N350 component, while fMRI demonstrates that the more severe the symptoms, the lower the BOLD signal changes in the mid-DLPFC.
authors.affiliation: Cognitive Neuroscience Unit, Montreal Neurological Institute and Hospital , Montreal, Canada.
authors.forename: Nadia
authors.initials: N
authors.lastname: Gosselin
authors.forename: Carolina
authors.initials: C
authors.lastname: Bottari
authors.forename: Jen-Kai
authors.initials: JK
authors.lastname: Chen
authors.forename: Michael
authors.initials: M
authors.lastname: Petrides
authors.forename: Simon
authors.initials: S
authors.lastname: Tinawi
authors.forename: Elaine
authors.initials: E
authors.lastname: de Guise
authors.forename: Alain
authors.initials: A
authors.lastname: Ptito
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology; D001921:Brain / Q000503:physiopathology*; D001930:Brain Injuries / Q000503:physiopathology* / Q000523:psychology; D001931:Brain Mapping; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D009483:Neuropsychological Tests; D011930:Reaction Time / Q000502:physiology; D012720:Severity of Illness Index