Dynamic links between theta executive functions and alpha storage buffers in auditory and visual working memory

Abstract

Working memory (WM) tasks require not only distinct functions such as a storage buffer and central executive functions, but also coordination among these functions. Neuroimaging studies have revealed the contributions of different brain regions to different functional roles in WM tasks; however, little is known about the neural mechanism governing their coordination. Electroencephalographic (EEG) rhythms, especially theta and alpha, are known to appear over distributed brain regions during WM tasks, but the rhythms associated with task-relevant regional coupling have not been obtained thus far. In this study, we conducted time–frequency analyses for EEG data in WM tasks that include manipulation periods and memory storage buffer periods. We used both auditory WM tasks and visual WM tasks. The results successfully demonstrated function-specific EEG activities. The frontal theta amplitudes increased during the manipulation periods of both tasks. The alpha amplitudes increased during not only the manipulation but also the maintenance periods in the temporal area for the auditory WM and the parietal area for the visual WM. The phase synchronization analyses indicated that, under the relevant task conditions, the temporal and parietal regions show enhanced phase synchronization in the theta bands with the frontal region, whereas phase synchronization between theta and alpha is significantly enhanced only within the individual areas. Our results suggest that WM task-relevant brain regions are coordinated by distant theta synchronization for central executive functions, by local alpha synchronization for the memory storage buffer, and by theta–alpha coupling for inter-functional integration.

Human Oscillatory EEG Activities Representing Working Memory Capacity

“…In our recent study using single visual and auditory WM tasks, the frontal theta activity was mainly observed during the manipulation period and not the maintenance periods, whereas posterior alpha activity was enhanced both in the manipulation and maintenance periods (Kawasaki et al, 2010). Building upon those previous findings, the present study demonstrated that frontal theta activity further increased in the dual WM task in comparison to the single VWM task, whereas parietal alpha activity did not differ between the single and dual WM tasks.…”

“…In addition to confirming previous reports that these oscillations are involved in VWM (; Klimesch et al, 2008;Jensen & Tesch, 2002;Jensen et al, 2002), the present study was able to dissociate their functions. Frontal theta activities have been associated with central executive functions including mental manipulation and calculation tasks (Kawasaki et al, 2010) and in supporting VWM storage during high-VWM loads and demands (Curtis & D'Esposito, 2003;Kawasaki & Watanabe, 2007;Sakai et al, 2002). Parietal alpha activity has been proposed to reflect simple WM storage.…”

“…Previous human scalp-recorded EEG studies have revealed modulated theta (about 4-8 Hz) and alpha (about 9-12 Hz) rhythms in distributed brain regions and phase synchronization between them during various WM tasks (Jensen & Tesche, 2002;Kawasaki & Watanabe, 2007;Klimesch et al, 2008;Mizuhara et al, 2004;Sauseng et al, 2005). Frontal theta activity in particular has been associated with the mental manipulation of WM, because these oscillations were enhanced in tasks such as mental calculation and image transfomation (Kawasaki et al, 2010). In contrast, posterior alpha activities are thought to be involved in the WM storage systems, because these oscillations are mainly observed in the retention intervals of many WM tasks.…”

“…To address this issue, measuring electrophysiological (EEG) data during WM tasks and analyzing the synchronizations in local areas and between different areas has proved particularly useful (Varela et al, 2001). Our previous EEG studies used mental calculation as the auditory WM task and mental spatial manipulation as the visual WM task (Kawasaki et al, 2010). The EEG results clearly demonstrated that the frontal theta (4-6 Hz) activity increased during the manipulation periods on both WM tasks, and the parietal and temporal alpha activities were enhanced only during the maintenance periods on the auditory and visual WM task, respectively.…”

A survey of affective brain computer interfaces: principles, state-of-the-art, and challenges

“…[52][53][54] The theta rhythm (4 to 8 Hz) has been observed during a number of cognitive processes, and its most prominent form, fronto-medial theta, is believed to originate from limbic and associated structures in the medial prefrontal cortex. [55][56][57][58] These theta oscillations subserve central executive function, integrating affective and cognitive sources of information, as necessary in working memory tasks [59,60] as well as in action monitoring. [58] Concerning affect, early reports mention an increasing 'hedonic' theta activity after interruption of pleasurable stimulation, but studies in children between 6 months and 6 years of age showed increases in theta activity upon exposure to pleasurable stimuli.…”