Exogenous attention interferes with endogenous attention processing via lateralized alpha power

Current theories of attention differentiate exogenous (bottom-up) from endogenous (top-down) orienting of visuospatial attention. While both forms of attentional processing engage different processes, endogenous and exogenous attention are thought to share processing resources, as shown by recent empirical evidence of their functional interactions. Here, we aim to uncover the neurobiological basis of how salient events that drive exogenous attention disrupts endogenous attention processes. We hypothesize that interference from exogenous attention over endogenous attention involves alpha-band activity, a neural marker of visuospatial attention. To test this hypothesis, we contrast the effects of endogenous attention across two experimental conditions: a single cueing condition where endogenous attention is engaged in isolation, and a double cueing condition where endogenous attention is concurrently engaged with exogenous attention. Our results are consistent with previous work and show that the concurrent engagement of exogenous attention interferes with endogenous attention processes. Importantly, we evaluate our main hypothesis using a moderated mediation model. We found that changes in alpha-band activity mediate the relationship between endogenous attention and its benefits on task performance, and that the interference of exogenous attention on endogenous attention occurs via the moderation of this indirect effect. Altogether, our results substantiate a model of attention, whereby top-down and bottom-up attentional processes compete for shared neurophysiological resources. This model accounts for the observed patterns of interference between exogenous and endogenous attention. Significance Statement Scientists differentiate top-down and bottom-up visuospatial attention processes. While bottom-up attention is rapidly engaged by emerging demands from the environment, top-down attention reflects slow voluntary shifts of attention. Several lines of research substantiate the idea that top-down and bottom-up attentional processes involve distinct brain systems. An increasing number of studies, however, argue that both attention systems share brain processing resources. The current study examines how salient visual events that engage bottom-up processes interfere with top-down processes. Using neurophysiological recordings and multivariate pattern classification techniques, the researchers show that both top-down and bottom-up attention processes do share brain resources expressed via alpha-band neurophysiological activity (8-12 Hz). The results further demonstrate that the interference patterns observed over brain activity in the alpha-band between both attention systems explains, in part, the interference between top-down and bottom-up attention at the behavioural level. The authors conclude by proposing a model of visuospatial attention whereby the dynamics between both attention systems are determined by their competition for limited brain processing resources.