Poster D120, Monday, March 27, 8:00 – 10:00 am, Pacific Concourse
Electrophysiological Evidence for Temporally Distinct Effects of Encoding, Maintenance, and Perceptual Fidelity in Object-Substitution Masking
Christine Salahub1, Stephen Emrich1; 1Brock University
Both visual working memory (VWM) and visual awareness researchers have studied an event-related potential (ERP) called the sustained posterior contralateral negativity (SPCN). In VWM tasks, this component is related to changes in working memory load, whereas in awareness-related tasks it is affected by changes in awareness of a target stimulus. However, no study has examined the effect of concurrent manipulations of set size and visual awareness on the SPCN component. Therefore, the goal of the current study was to examine how set size and masking manipulations would interact to affect SPCN amplitude. To examine thresholds of awareness we used an object-substitution masking (OSM) paradigm. In this task, a sparse four-dot mask surrounds a target item and offsets at a slightly later time than the target. Twenty participants were shown either two or four Landolt Cs from which they had to find the target (masked or unmasked). The two manipulations had temporally distinct effects on the SPCN; mask condition had a significant effect in the early delay period (eSPCN) and set size in the late period (lSPCN). The eSPCN had greater amplitude during masked trials, whereas the lSPCN increased in amplitude for larger set sizes. Additionally, both early and late SPCN amplitudes were related to response precision, such that more precise responses resulted in greater amplitude than less precise responses. Overall, results from this study demonstrate that the SPCN reflects multiple processes occurring over time, including working memory encoding and maintenance as well as the fidelity of information maintained in memory.
Topic Area: PERCEPTION & ACTION: Vision