Spatial but not temporal orienting of attention enhances the temporal acuity of human peripheral vision in an ecologically valid scenario

The temporal acuity of a sensory system determines its capacity to detect delays between events, which enables ordering the events in time and adapting behaviors accordingly. Whether and how voluntary attention drives visual temporal acuity is still unclear, especially in peripheral vision. Here, we present a psychophysical study aimed at 1) evaluating whether cue-based spatial and temporal orientation of visual attention modulates the temporal acuity in peripheral vision, 2) assessing to what extent these modulations rely on shared or distinct mechanisms, and 3) exploring whether these modulations are cumulative or independent from each other. To address these goals, forty participants performed an ecologically valid asynchrony detection task in immersive virtual reality whilst electroencephalographic and pupillary dynamics were recorded. We found non-cumulative reductions of pupil constriction during the processing of cues orienting attention in space and time. This suggests that pupil size represents a readout of the formation of cue-based spatiotemporal expectations about visual targets. We further found that pre-target oscillatory dynamics in posterior theta and alpha bands are suppressed by both spatial and temporal orienting of visual attention, with cumulative effects, while beta band activity remains unaffected. These modulations provide evidence for shared and interactive top-down mechanisms of explicit spatial and temporal attention on visual temporal processing. Yet, despite these modulations, only explicit spatial orienting enhances the sensitivity to asynchronies. Implicit, but not cue-based temporal orienting increased task performance. This highlights that explicit endogenous attention directed to space – but not to time – increases the temporal acuity of peripheral vision. Overall, these results cast unambiguous doubts on the accepted trade-off that spatial attention always meliorate spatial visual acuity while impeding temporal visual acuity, and thus call for the further refinement of models of visual attention.