Saccade Target Status Influences the Reference Frame of Object-Location Binding

Despite constant retinal image shifts caused by saccadic eye movements, humans perceive external environments as stable. To achieve perceptual stability across saccades, the visual system must update spatial information (remapping) and keep track of non-spatial information bound to each location (object-location binding). Here, we investigated whether saccade target status affects the reference frame of object-location binding across saccades. Previous studies examining the reference frame of object-location binding showed that objects that appear at peripheral, non-saccade target locations are naturally bound to retinotopic, not spatiotopic, coordinates. But real-world saccades are generally directed towards objects of interest: Might trans-saccadic object-location binding occur in more ecologically relevant spatiotopic coordinates for objects with saccade target status? We adopted a modified spatial congruency bias paradigm, in which participants were asked to judge if two objects presented sequentially have the same or different identity. In Experiment 1, we inserted a saccade between object presentation, directed either towards the first object’s location (saccade-target condition) or to another location (saccade-elsewhere condition). We found purely retinotopic object-location binding in the saccade-elsewhere condition (replicating previous reports), but co-existing spatiotopic and retinotopic binding in the saccade-target condition, indicating that saccade target objects can be additionally bound to spatiotopic coordinates across saccades. In Experiment 2, we added a saccade-away condition, in which participants saw the first object at fovea and launched a saccade away from that location. We again found significant spatiotopic and retinotopic object-location binding in the saccade-target condition, but only retinotopic binding in the saccade-away condition, suggesting that it is the saccade target status specifically that allows an object to be additionally bound to spatiotopic coordinates. Overall, the results highlight the important role of saccade targets in maintaining stability across saccades, allowing for object-location binding to be encoded and/or remapped in more ecologically relevant spatiotopic coordinates.