An Investigation into ERP Measures of Attention and Awareness using Object-Substitution Masking

Abstract

Attention and awareness are cognitive processes that can be investigated using electrophysiological recordings of brain activity. Fluctuations of electrical potentials in response to cognitive tasks reflect processes such as selective attention (N2pc) and visual working memory maintenance (SPCN). Previous research on these event-related potentials (ERPs) has demonstrated that they are affected by a variety of experimental manipulations, such as changes in set size, visual awareness, and memory fidelity. The current study aimed to examine how both set size and visual awareness (manipulated using object-substitution masking; OSM) affected the N2pc and SPCN components. Although researchers have previously examined the effect of set size and masking on these components, the manipulations have never been done concurrently. In the current study, it was found that completing an OSM task involved several stages of processing, reflected by temporally distinct ERP components. The N2pc was affected by set size, such that larger set sizes required greater attentional selection (i.e., larger N2pc amplitude) to locate the target. The SPCN component reflected separate effects of set size and mask, such that mask had an effect in the early delay period (eSPCN) and set size in the late period (lSPCN). Both early and late SPCN amplitudes were also 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 N2pc and SPCN components reflect multiple processes occurring over time, such as attentional selection, working memory encoding and maintenance, and the fidelity of information maintained in memory.