title: Fronto-parietal and fronto-temporal theta phase synchronization for visual and auditory-verbal working memory.
abstract: In humans, theta phase (4-8 Hz) synchronization observed on electroencephalography (EEG) plays an important role in the manipulation of mental representations during working memory (WM) tasks; fronto-temporal synchronization is involved in auditory-verbal WM tasks and fronto-parietal synchronization is involved in visual WM tasks. However, whether or not theta phase synchronization is able to select the to-be-manipulated modalities is uncertain. To address the issue, we recorded EEG data from subjects who were performing auditory-verbal and visual WM tasks; we compared the theta synchronizations when subjects performed either auditory-verbal or visual manipulations in separate WM tasks, or performed both two manipulations in the same WM task. The auditory-verbal WM task required subjects to calculate numbers presented by an auditory-verbal stimulus, whereas the visual WM task required subjects to move a spatial location in a mental representation in response to a visual stimulus. The dual WM task required subjects to manipulate auditory-verbal, visual, or both auditory-verbal and visual representations while maintaining auditory-verbal and visual representations. Our time-frequency EEG analyses revealed significant fronto-temporal theta phase synchronization during auditory-verbal manipulation in both auditory-verbal and auditory-verbal/visual WM tasks, but not during visual manipulation tasks. Similarly, we observed significant fronto-parietal theta phase synchronization during visual manipulation tasks, but not during auditory-verbal manipulation tasks. Moreover, we observed significant synchronization in both the fronto-temporal and fronto-parietal theta signals during simultaneous auditory-verbal/visual manipulations. These findings suggest that theta synchronization seems to flexibly connect the brain areas that manipulate WM.
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 Ibaraki, Japan ; Laboratory for Advanced Brain Signal Processing, RIKEN Brain Science Institute Saitama, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kawasaki
authors.affiliation: Rhythm-based Brain Information Processing Unit, RIKEN BSI-TOYOTA Collaboration Center Ibaraki, Japan ; Laboratory for Advanced Brain Signal Processing, RIKEN Brain Science Institute Saitama, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Kitajo
authors.affiliation: Neuroinformatics Japan Center, RIKEN Brain Science Institute Saitama, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yamaguchi
keywords: auditory; electroencephalogram; synchronization; visual; working memory