Top-down control of the left visual field bias in cued visual spatial attention

Abstract

A left visual field (LVF) bias in perceptual judgements, response speed and discrimination accuracy are well documented in humans. However, LVF bias can be modulated by perceptual and task demands. For example, cuing spatial attention can reduce or eliminate the LVF bias, suggesting that attentional control can compensate for the LVF bias. We investigated this possibility directly by recording pupillometry together with fMRI in a cued visual spatial attention task. Prior to the onset of a task-relevant target stimulus, we observed that the pupil was significantly more dilated following attend-right than attend-left cues even though task performance did not differ. This difference in pupil dilation was inversely related to the corresponding difference in later target-evoked pupil dilation and in the reaction times to those targets, suggesting that an increased attentional effort was triggered by the attend-right cues, and this offset the LVF bias, equating behavioral performance. The differences in pupil dilation to the right versus left hemifield were correlated with corresponding fMRI differences primarily in the right hemisphere, supporting the idea that the increased attentional effort for rightward attention is mediated by activity in right hemisphere networks, which illuminates how attentional control mediates attentional biases in vision.