title: Mild traumatic brain injury: graph-model characterization of brain networks for episodic memory.
abstract: Episodic memory is among the cognitive functions that can be affected in the acute phase following mild traumatic brain injury (MTBI). The present study used EEG recordings to evaluate global synchronization and network organization of rhythmic activity during the encoding and recognition phases of an episodic memory task varying in stimulus type (kaleidoscope images, pictures, words, and pseudowords). Synchronization of oscillatory activity was assessed using a linear and nonlinear connectivity estimator and network analyses were performed using algorithms derived from graph theory. Twenty five MTBI patients (tested within days post-injury) and healthy volunteers were closely matched on demographic variables, verbal ability, psychological status variables, as well as on overall task performance. Patients demonstrated sub-optimal network organization, as reflected by changes in graph parameters in the theta and alpha bands during both encoding and recognition. There were no group differences in spectral energy during task performance or on network parameters during a control condition (rest). Evidence of less optimally organized functional networks during memory tasks was more prominent for pictorial than for verbal stimuli.
authors.affiliation: Department of Medicine, Clinical Research Laboratory Widén, University of Crete, 71409 Iraklion/Crete Greece. tsirkav@yahoo.com
authors.forename: Vasso
authors.initials: V
authors.lastname: Tsirka
authors.forename: Panagiotis G
authors.initials: PG
authors.lastname: Simos
authors.forename: Antonios
authors.initials: A
authors.lastname: Vakis
authors.forename: Kassiani
authors.initials: K
authors.lastname: Kanatsouli
authors.forename: Michael
authors.initials: M
authors.lastname: Vourkas
authors.forename: Sofia
authors.initials: S
authors.lastname: Erimaki
authors.forename: Ellie
authors.initials: E
authors.lastname: Pachou
authors.forename: Cornelis Jan
authors.initials: CJ
authors.lastname: Stam
authors.forename: Sifis
authors.initials: S
authors.lastname: Micheloyannis
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001921:Brain / Q000503:physiopathology*; D001930:Brain Injuries / Q000150:complications* / Q000209:etiology / Q000473:pathology; D001931:Brain Mapping; D058256:Brain Waves / Q000502:physiology; D004569:Electroencephalography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000209:etiology* / Q000473:pathology*; D009483:Neuropsychological Tests; D021641:Recognition, Psychology; D013057:Spectrum Analysis; D013223:Statistics as Topic; D055815:Young Adult