title: Theta-alpha EEG phase distributions in the frontal area for dissociation of visual and auditory working memory.
abstract: Working memory (WM) is known to be associated with synchronization of the theta and alpha bands observed in electroencephalograms (EEGs). Although frontal-posterior global theta synchronization appears in modality-specific WM, local theta synchronization in frontal regions has been found in modality-independent WM. How frontal theta oscillations separately synchronize with task-relevant sensory brain areas remains an open question. Here, we focused on theta-alpha phase relationships in frontal areas using EEG, and then verified their functional roles with mathematical models. EEG data showed that the relationship between theta (6 Hz) and alpha (12 Hz) phases in the frontal areas was about 1:2 during both auditory and visual WM, and that the phase distributions between auditory and visual WM were different. Next, we used the differences in phase distributions to construct FitzHugh-Nagumo type mathematical models. The results replicated the modality-specific branching by orthogonally of the trigonometric functions for theta and alpha oscillations. Furthermore, mathematical and experimental results were consistent with regards to the phase relationships and amplitudes observed in frontal and sensory areas. These results indicate the important role that different phase distributions of theta and alpha oscillations have in modality-specific dissociation in the brain.
authors.affiliation: Research Institute for Electronics Science, Hokkaido University, Sapporo, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Akiyama
authors.affiliation: Institute of Math for Industry, Kyushu University, Fukuoka, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tero
authors.affiliation: Department of Intelligent Interaction Technology, Graduate School of Systems and Information Engineering, University of Tsukuba, Tsukuba, Japan.|Rhythm-based Brain Information Processing Unit, RIKEN BSI-TOYOTA, Collaboration Center, Saitama, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kawasaki
authors.affiliation: WPI Advanced Institute for Materials Research Tohoku University, Sendai, Japan.
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Nishiura
authors.affiliation: Neuroinformatics Japan Center, RIKEN Brain Science Institute, Saitama, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yamaguchi
mesh_terms: D000328:Adult; D000513:Alpha Rhythm; D001307:Auditory Perception; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D006801:Humans; D008297:Male; D008570:Memory, Short-Term; D008959:Models, Neurological; D013826:Theta Rhythm; D014796:Visual Perception