| dc.description.abstract | Everyday activities – like reading an email, watching a football match, scrolling through social media, or window-shopping – all involve quickly scanning complex visual scenes using rapid eye movements called “saccades.” Saccades bring important parts of the environment into foveal focus, not only for high-acuity visual analysis (perceptual sensitivity), but also for prioritized decision-making (choice bias). Surprisingly, even before the eyes move, planning to make a saccade can produce attention-like benefits – both perceptual and decisional – at the target of the intended eye movement. Yet, whether the same neural mechanisms mediate saccade planning and visual attention remains a topic of active research. Here, I explore the link between saccades, and three different varieties of attention – presaccadic, external and internal – employing novel psychophysics, high-resolution eye-tracking, Bayesian modeling of behavior, and analysis of brain recordings.
In the first aim, I studied the link between eye movements and “presaccadic” attention – a perceptual benefit that occurs immediately before the eyes move. While presaccadic attention benefits are well documented in discrimination tasks, whether such also occur in detection tasks was unknown. Using a novel dual-task paradigm requiring a saccade prior to detecting and localizing changes, I found a surprising lack of presaccadic benefit in perceptual sensitivity, but a robust increase in choice bias, toward the saccade target, immediately prior to the saccade. To probe this further, I conducted an orientation estimation task which revealed a “presaccadic recency bias” at the saccade target, owing to which orientation estimates for the final stimulus were perceptually biased towards the initial stimulus, thereby rendering presaccadic change detection challenging. Analysis with a Bayesian model showed how perceptual and choice biases interacted to fully explain the effects of presaccadic attention on change detection.
In the second aim, I investigated the link between eye movements and “external” attention – attention directed to objects in the external visual world. Covert attention – orienting attention without shifting gaze – is often also accompanied by concurrent saccade planning toward the attended location. This leaves open the question of whether saccade planning and covert attention rely on shared or distinct mechanisms. Using an antisaccade response to report change detection, I found that perceptual sensitivity and choice bias were enhanced at both the covertly attended and the saccade target locations, suggesting that covert attention and saccade planning operate through putatively distinct mechanisms. Confirming these findings, analysis of behavior and neural recordings from visual area V4 of monkeys performing an antisaccade task (Steinmetz & Moore, 2014) revealed that while covert attention selectively modulated bias and V4 neural firing rates, saccade planning selectively modulated sensitivity and V4 pairwise noise correlations.
In the third aim, I explored the link between eye movements and “internal” attention – attention directed to items in visual working memory (WM). Although saccades and covert attention are known to be linked, how gaze mechanisms contribute to selection in WM has remained largely unexplored. To address this gap, I conducted a task where participants planned saccades to a "spatially tagged" location while maintaining oriented stimuli in their WM. Planning a saccade resulted in an automatic selection of memorized information at the saccade target location. In addition, the magnitude of this selection was predicted by directional biases in tiny fixational eye movements called “microsaccades,” uncovering a physiological marker linking gaze biases and prioritization in WM. Remarkably, I observed nearly identical effects even with manual responses without overt saccades, showing that such “spatial tagging” leads to reflexive selection in visual WM regardless of response modality.
In summary, these findings offer new insights into how eye movements interact with external and internal attention, with important implications for understanding behavior in naturalistic contexts such as driving or visual search, as well as for clinical conditions involving attentional or oculomotor dysfunction, including attention-deficit/hyperactivity disorder (ADHD). | en_US |
