Distinct Mechanisms of Surround Modulation for Dynamic Natural Scenes in Motion-and Scene-Selective Cortex

Surround modulation refers to changes in neural responses to a central stimulus induced by its surrounding context, which can manifest as either suppression or facilitation. Although this phenomenon is well established for simple stimuli, its underlying neural mechanism during natural scene perception remains unclear. Using fMRI, we examined how motion congruence and categorical similarity between central and surrounding scenes shape surround modulation across the visual hierarchy. Central and surrounding scenes systematically varied in categorical similarity (identical exemplar, different exemplar of the same basic-level category, different basic-level category, or different superordinate category) and in motion direction (same or opposite direction). Neural responses were measured in primary visual cortex (V1), motion-selective cortex (hMT+), and scene-selective occipital and parahippocampal place areas (OPA and PPA). hMT+ showed robust motion-dependent surround suppression, which was stronger for same-direction motion. In contrast, V1 showed surround facilitation across all conditions, which was reduced when center and surround were identical and moved in the same direction, consistent with sensitivity to physical similarity. OPA and PPA primarily exhibited facilitation. Multivariate decoding between center-only and center-surround conditions complemented these findings, revealing motion-dependent surround modulation in hMT+, and category-dependent surround modulation in OPA and PPA. Across the visual hierarchy, surrounding scene context thus systematically attenuates redundant input or enhances informative differences: from low-level facilitation in V1 to motion-dependent suppression in hMT+ and category-dependent modulation in scene-selective regions.