Abstract
We can focus our visual spatial attention by covertly attending to relevant locations, moving our eyes, or both simultaneously. How does shifting versus holding covert attention during fixation compare with maintaining covert attention across saccades? We acquired fMRI data during a combined saccade and covert attention task. Participants began each trial by fixating a cross while covertly attending to one of multiple peripheral rapid serial visual presentation (RSVP) streams. There were four critical conditions. On eyes-fixed trials, participants either held attention at the same initial location (“hold attention”) or shifted attention to another stream midway through the trial (“shift attention”). On eyes-move trials, participants made a saccade midway through the trial, while maintaining attention in one of two reference frames: “retinotopic attention” and “spatiotopic attention”. The retinotopic condition involved holding attention at a fixation-relative location but shifting to a different stream relative to the screen, whereas the spatiotopic condition involved holding attention on the same screen-centered location but shifting relative to the eyes. We localized the brain network sensitive to attention shifts (shift>hold attention), and used multivariate pattern time course (MVPTC) analyses to compare whether patterns of brain activity for spatiotopic and retinotopic conditions were more similar to shifting or to holding attention. In the attention shift network, we found transient information both about whether covert shifts were made and whether saccades were executed; additionally, both retinotopic and spatiotopic conditions were represented more similarly to shifting than to holding attention. In contrast, an exploratory searchlight analysis revealed some additional regions where retinotopic attention was relatively more similar to “hold” while spatio-topic more to “shift”, and some other regions, vice versa. Thus, maintaining retinotopic and spatiotopic attention across saccades may involve different types of updating that might be represented with “hold” and “shift” signals combined across different sets of regions.
Acknowledgement: NIH R01-EY025648 (JG), Alfred P. Sloan (JG), H. Dean and Susan Regis Gibson Award 2016 (XZ)