Neural representations of covert attention across saccades: comparing pattern similarity to shifting and holding attention during fixation

Abstract

We can focus visuospatial 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 human fMRI data during a combined saccade and covert attention task. On Eyes-fixed trials, participants either held attention at the same initial location (“hold attention”) or shifted attention to another location 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: The “retinotopic attention” condition involved holding attention at a fixation-relative location but shifting to a different screen-centered location, whereas the “spatiotopic attention” condition involved holding attention on the same screen-centered location but shifting relative to fixation. We localized the brain network sensitive to attention shifts (shift > hold attention), and used multivoxel pattern time-course analyses to investigate the patterns of brain activity for spatiotopic and retinotopic attention across saccades. In the attention shift network, we found transient information about both whether covert shifts were made and whether saccades were executed. Moreover, in this network, both retinotopic and spatiotopic conditions were represented more similarly to shifting than to holding covert attention. An exploratory searchlight analysis revealed additional regions where spatiotopic was relatively more similar to shifting and retinotopic more to holding. Thus, maintaining retinotopic and spatiotopic attention across saccades may involve different types of updating that vary in similarity to covert attention “hold” and “shift” signals across different regions.

Significance Statement To our knowledge, this study is the first attempt to directly compare human brain activity patterns of covert attention (to a peripheral spatial location) across saccades and during fixation. We applied fMRI multivoxel pattern time course analyses to capture the dynamic changes of activity patterns, with specific focus on the critical timepoints related to attention shifts and saccades. Our findings indicate that both retinotopic and spatiotopic attention across saccades produce patterns of activation similar to “shifting” attention in the brain, even though both tasks could be interpreted as “holding” attention by the participant. The results offer a novel perspective to understand how the brain processes and updates spatial information under different circumstances to fit the needs of various cognitive tasks.