The ERP correlates of color-based center-surround inhibition in working memory

The color-based center-surround inhibition (CSI) in working memory (WM) refers to that remembering a color inhibits the memory of similar colors but not of distinct colors. This study aimed to investigate the neural activity of color-based CSI in WM. Two WM items (distance 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, or 60 degrees in color space) were displayed sequentially, then one of them was retrieved to compare with a later probe. Behavioral results revealed that participants showed longer RTs for distances 20 degrees and 30 degrees than distances 0 degrees and 40 degrees, suggesting a CSI be-tween similar items. ERP results revealed that: 1) WM item-induced late positive component (LPC) was more positive for distance 30 degrees than the other distances, suggesting an enhanced resource allocation process for encoding similar items; 2) Cue-induced LPC was more positive for distances 20 degrees and 30 degrees than distances 0 degrees and 60 degrees, suggesting a greater difficulty for retrieving similar items; Cue-induced contingent negative variation was less negative for distance 20 degrees than distances 40 degrees, 50 degrees, and 60 degrees, suggesting a reduced response preparation process during retrieving similar items; 3) Probe-induced LPC was more positive for distances 20 degrees and 30 degrees than distances 50 degrees and 60 degrees, suggesting a greater effort for comparing probe with one item retrieved from two similar items. These results revealed a colored-based CSI during WM encoding and retrieval processes. An enhanced top-down control might be required to resolve the greater interference between similar items than identical or distinct items conditions.