Shared neurophysiological resources between exogenous and endogenous visuospatial attentional processes

Abstract

Prevailing accounts of visuospatial attention differentiate exogenous orienting, which corresponds to involuntary shifts of attention, from endogenous orienting, which reflects the voluntary control of attention. While these different forms of attention are functionally separable, evidence shows that they can nevertheless interact with each other. These dynamics have been at the center of ongoing debates for more than two decades. One hypothesis regarding these interactions is that, while both forms of attention orienting map onto independent functional systems, they are capable of mutual interference. This viewpoint implies that exogenous attention, a ballistic and stimulus-driven process, is not impervious to the influence of endogenous attention. Evidence in support of this view remains sparse and the central factors that underlie these interactions remain largely unknown. The present study tackles these questions by examining whether endogenous attention influences the neural processes of exogenous attention by applying multivariate pattern classification to electroencephalography (EEG). We contrasted the cue-related and target-related effects of exogenous attention across two experimental conditions: Single cueing where exogenous attention is engaged alone, and double cueing where exogenous attention is concurrently engaged with endogenous attention. Our results show that the simultaneous engagement of endogenous attention alters the emergence of exogenous attention across cue-related and target-related processes. Therefore, exogenous attention is not impervious to the influence of endogenous attention. Importantly, we observed that classifiers trained to decode exogenous attention from alpha band activity during single cueing condition were misled by the direction of endogenous attention when tested in the context of double cueing. Our research therefore provides evidence of overlap between exogenous and endogenous attention and emphasizes that limited neural resources play a central role in the dynamics between both forms of attention orienting.