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.

TMS-induced theta phase synchrony reveals a bottom-up network in working memory

“…In particular, theta rhythms in distributed brain regions are considered to interact with each other [7,8]. Moreover, it has been suggested that low-frequency synchronizations connect the frontal area with posterior sensory areas for the executive system [9,10,11]. However, network directionality of such interactions in WM is not clear; either top-down or bottom-up mechanisms which are defined as signals from sensory to frontal areas or signals from frontal to sensory areas, respectively in this study.…”

“…were performed [10], and single-pulse TMS was delivered to three target areas (frontal area, visual area, auditory area). The tasks were also performed during sham-TMS and within a no-TMS condition.…”

Corticothalamic network dysfunction and behavioral deficits in a mouse model of Alzheimer's disease

“…Theta rhythms also have been shown to facilitate the formation of long-range functional networks, sometimes referred as theta synchronization (Buzsaki and Draguhn, 2004,Mellem, et al, 2013,von Stein and Sarnthein, 2000). During cognitive processing, including visual and auditory stimuli, theta synchronization/coupling helps in recruitment of various neural network and information co-ordination among distinct neuroanatomical structures (Kawasaki, et al, 2014). EEG studies in AD patients have also shown altered delta and theta power (Fraga, et al, 2013,Huang, et al, 2000,Jeong, 2004,van Deursen, et al, 2008), although they also exhibit a decrease in alpha and beta frequency band power (Fraga, et al, 2013,Jeong, 2004).…”

Dynamics of auditory working memory

“…Shifts of attention to auditory objects held in working memory were associated with the activation of fronto-parietal attention systems, and further temporal and parietal activations distinguished between spatial and category-related attention cues ( Backer et al, 2015 ). Mental transformation and updating of auditory memory contents involved increased frontal and temporal theta power and enhanced fronto-temporal theta phase synchrony ( Kawasaki et al, 2010 , 2014 ).…”