The influence of spatial and temporal attention on visual awareness - a behavioral and ERP study

Abstract

Whether attention is a prerequisite of perceptual awareness or, conversely, an independent and dissociable process remains a matter of debate. Importantly, understanding the relation between attention and awareness is unlikely without taking into account that both are heterogeneous and multifaceted mechanisms. Therefore, the present study tested the impact of two attentional mechanisms proposed by the Posner model - temporal alerting and spatio-temporal orienting - on visual awareness. Specifically, we evaluated the effects of attention on the perceptual level, by measuring objective and subjective awareness of a threshold-level stimulus; and on the neural level, by investigating how attention affects two postulated ERP correlates of awareness. We found that both alerting and orienting mechanisms additively facilitate perceptual consciousness, with activation of the latter resulting in most vivid awareness. Further, we provide evidence that the late positivity (LP) is unlikely to constitute a neural correlate of consciousness, as its amplitude was modulated by both attentional mechanisms, but the early visual awareness negativity (VAN) might reflect an attention-independent mechanism of awareness. In conclusion, our study reveals a nuanced relationship between attention and awareness and, by investigating the effect of the alerting mechanism, provides insights into the role of temporal attention in perceptual consciousness.