# Orientation-tuned surround-suppression is strongest within perceived 3D surfaces

## TL;DR

The study shows that the strength of orientation-tuned surround suppression depends on whether the visual elements are perceived as part of the same 3D surface.

## Contribution

It reveals that perceived 3D surface continuity, not just depth, modulates suppressive visual interactions.

## Key findings

- Suppression is strongest when the surround forms a continuous 3D surface with the center.
- Disparity alone does not determine suppression strength; surface continuity is more important.
- Perceived surface organization influences neural interactions in early vision.

## Abstract

Our perception of contrast is strongly affected by contextual factors. A well-known example is that of orientation-tuned surround suppression (OTSS). Surrounds have more suppressive effects on the perceived contrast of the center when they have the same orientation. This phenomenon has been linked to horizontal interactions within the early visual cortex. Here we show that the strength of suppression is modulated strongly by the perceived three-dimensional structure of the scene. Placing the surround at a different retinal disparity, and therefore perceived depth, decreased OTSS, regardless of whether the surround was placed behind or in front of the center. The difference in disparity was, however, not the key determinant of the strength of OTSS. Suppressive interactions were strongest when the surround formed a three-dimensional surface that was continuous with the center and weaker when the surround seemed to be part of a separate surface, even when the surround seemed to be closer to the center in perceived depth. The results suggest that visual features that are perceived to form part of the same surface can engage in stronger suppressive interactions than those perceived to lie on different surfaces. This raises questions about how the underlying neural interactions become restricted to surfaces and support the view that top-down information about perceptual organization can gate interactions occurring at lower levels in the visual system.