The Active Side of Stereopsis: Fixation Strategy and Adaptation to Natural Environments

Agostino Gibaldi,Silvio P Sabatini,Andrea Canessa

doi:10.1038/srep44800

Abstract

Depth perception in near viewing strongly relies on the interpretation of binocular retinal disparity to obtain stereopsis. Statistical regularities of retinal disparities have been claimed to greatly impact on the neural mechanisms that underlie binocular vision, both to facilitate perceptual decisions and to reduce computational load. In this paper, we designed a novel and unconventional approach in order to assess the role of fixation strategy in conditioning the statistics of retinal disparity. We integrated accurate realistic three-dimensional models of natural scenes with binocular eye movement recording, to obtain accurate ground-truth statistics of retinal disparity experienced by a subject in near viewing. Our results evidence how the organization of human binocular visual system is finely adapted to the disparity statistics characterizing actual fixations, thus revealing a novel role of the active fixation strategy over the binocular visual functionality. This suggests an ecological explanation for the intrinsic preference of stereopsis for a close central object surrounded by a far background, as an early binocular aspect of the figure-ground segregation process.

Highlights

As a complicating factor, our eyes constantly shift position to explore the visual scene, requiring to recompute retinal disparity at each fixation
We investigate the possible role of active fixation strategy on the binocular visual system
The obtained disparity distributions were analyzed with respect to random fixations of a virtual observer, evidencing a direct influence of the active fixation strategy over the sensory experience of the 3D environment

Summary

Introduction

Our eyes constantly shift position to explore the visual scene, requiring to recompute retinal disparity at each fixation. Actual human fixation is preferentially directed towards close targets within the visual scene[21,22,23], and behaviorally significant points more likely attract our gaze This strategy allows us gaining accurate visual information about the environment and eventually to plan and accomplish different tasks, such as object recognition, grasping, and manipulation[24]. The mechanism of stereopsis exhibit a fine retinotopic adaptation to the working environment, evidencing how fixation strategy conditions the functional characteristics of the visual system This suggests an ecological explanation of the intrinsic preference of the early neural mechanism of stereopsis for a close central object surrounded by a far background, specialized in higher visual areas, as a binocular aspect of the figure-ground segregation process

Methods

Results

Discussion

Conclusion