The neural mechanisms of percept-memory comparison in visual working memory

Researchers have revealed that comparing the perceptual input with the representations stored in visual working memory initiates a rapid attention-shift, which is predominantly triggered by the relevant-feature change. The comprehension of the change contents further necessitates a follow-up comparison that contrasts all the object features regardless of the task relevancy. However, whether such a distinct stage exists and how the process is carried on need further verification. We explored this issue by investigating the underlying neural mechanisms of the percept-memory comparison. By recording EEG, we found that both the task-relevant and -irrelevant feature changes elicited significantly more negative anterior N2 waves (230-340ms) rooting in the anterior cingulate cortex (ACC), and meanwhile activated the frontal theta (5-8Hz, 250-550ms). These results suggest that a distinct comparison stage does exist, which is supported by the anterior N2, ACC and frontal theta.