Dorsomedial occipital cortex participates in a cortical network for transsaccadic feature discrimination

Abstract

To date, the cortical correlates of human transsaccadic vision have only been probed with single object features such as orientation (associated with repetition suppression in the supramarginal gyrus; SMG) and spatial frequency (associated repetition enhancement in dorsomedial occipital cortex; cuneus). Here, we used functional magnetic resonance imaging to identify cortical modulations associated with transsaccadic discrimination of multiple object features. Participants (n=21) viewed a 2D object and then, after sustained fixation or a saccade, judged whether the shape or orientation of the re-presented object had changed. Since feature change was randomized, participants had to remember both features across saccades to perform the task. A bilateral region-of-interest (ROI) analysis was performed, based on the previously identified SMG and Cuneus sites. Of these, only cuneus was modulated here by both saccades and feature (i.e., orientation vs. shape) discrimination. A whole-brain voxelwise contrast (Saccade > Fixation; n=17), followed by a search within significant clusters for feature modulation, confirmed peak modulation in left cuneus. Used as a seed region for network analysis, this site showed contralateral functional connectivity with early visual cortex (lingual gyrus), object-processing areas (occipitotemporal cortex) and saccade/motor areas in parietal cortex. These observations show that medial occipital cortex participates in a cortical network involved in transsaccadic feature discrimination. Together with the previous literature, this suggests that separate mechanisms exist for transsaccadic perception of intrinsic (spatial frequency, shape) versus extrinsic (location, orientation) object features, but these mechanisms may not simply summate to perform more complex multi-feature tasks.