Abstract
Goal: What role do microsaccades play in temporal attention deployed at different visual field locations? Rationale: Temporal attention is how we can prioritize specific moments in time to improve behavioral performance. Temporal attention enhances performance similarly at foveal and parafoveal locations, for which discriminability varies (Fernández, Denison & Carrasco, 2019). Deployment of temporal attention suppresses microsaccade (small fixational eye movements (<1°)) rate in anticipation of target presentation thus stabilizing fixation (Denison, Yuval-Greenberg & Carrasco, 2019). Methods: Observers performed 2IFC orientation discrimination task, while directed with a precue tone to deploy temporal attention to one of two (or both, neutral condition) Gabor patches presented serially (SOA: 250 ms) at the same blocked target location: fovea, right horizontal meridian (RHM) or upper vertical meridian (UVM) at 4°. Eye fixation was monitored throughout, and microsaccades were extracted using a standard velocity-based detection algorithm. Results: The effects of temporal attention were similar in trials with and without microsaccades (from cue onset to stimulus offset). Microsaccade rates were significantly more suppressed in anticipation of target presentation when the target was at the fovea than at the RHM. Across locations, in anticipation of target presentation, microsaccades are more suppressed in attention than in neutral trials. Furthermore, stimulus field location significantly modulated microsaccade direction. Specifically, more microsaccades were directed along the horizontal meridian for the RHM, and towards the upper visual field for the UVM. Thus, the traditionally reported horizontal bias for microsaccade direction was not found in the UVM condition. Conclusions: These results provide evidence that temporal attention modulates microsaccade rate, and visual field location modulates microsaccade direction, despite similar performance benefits of temporal attention around the visual field.