Abstract
During the comparison stage of visual working memory (VWM) processing, detecting the mismatch between the external sensory input and internal representations is a crucial cognitive ability for human, but the neural mechanism behind it remains largely unclear. The present study investigated the role of frontal theta power in detecting the mismatched information in VWM in a delayed matching task. A control task required to compare two simultaneously presented visual figures was also designed as a contrast to exclude the possibility that frontal theta activity just reflecting the non-memory-related behavioral conflicts. To better characterize the control mechanisms shaped by the frontal theta oscillation in human VWM, colored shapes were adopted as materials while both the task-relevant shape feature and task-irrelevant color feature could be mismatched. We found that the response times of participants were significantly delayed under the relevant- and irrelevant-mismatch conditions in both tasks and the conjunction-mismatch condition in delayed matching task. While our EEG data showed that increased frontal theta power was only observed under the relevant- and conjunction-mismatch conditions in the delayed matching task, but not the control task. These findings suggest that the frontal distributed theta activity observed here reflects the detection of mismatched information during the comparison stage of VWM, rather than the response-related conflicts. Furthermore, it is consistent with the proposal that theta-band oscillation can act as a control mechanism in working memory function so that the target-mismatched information in VWM could be successfully tracked. We also propose a possible processing structure to explain the neural dynamics underlying the mismatch detection process in VWM.
Highlights
As a pivotal cognitive system, working memory allows for transiently storing and utilizing of information (Baddeley, 1992, 2001)
In terms of the response time (RT), a 2 × 4 repeatedmeasures analysis of variance (ANOVA) revealed a significant interaction between task type and mismatch type [F(3,57) = 5.48, p < 0.05, η2p = 0.22] and a significant mismatch type main effect [F(3,57) = 23.89, p < 0.01, η2p = 0.56], but no significant task main effect [F(1,19) = 0.86, p = 0.37]
The main effect of mismatch type in delayed matching task was confirmed by the data-driven analysis, which showed significant difference in theta-band power of the frontal region (Figure 4B) with a similar time-frequency regions of interest (TF-ROIs)
Summary
As a pivotal cognitive system, working memory allows for transiently storing and utilizing of information (Baddeley, 1992, 2001). As a function of this cognitive system, comparing the representations stored in visual working memory (VWM) with the perceptual input is of considerable importance to both high-level and low-level visual processing (Luck, 2008). This process requires updating relevant memory representations and adjusting the current cognitive operation, which promotes appropriate behavior in accordance with the external environment (Hollingworth et al, 2008; Richard et al, 2008). Little is known about whether there are any neural oscillations that corresponding to this control processing
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