Straub Dominik, Rothkopf Constantin A
Institute of Psychology, Technical University of Darmstadt, Darmstadt, Germany.
Centre for Cognitive Science, Technical University of Darmstadt, Darmstadt, Germany.
Front Psychol. 2021 Feb 22;12:641471. doi: 10.3389/fpsyg.2021.641471. eCollection 2021.
The efficient coding hypothesis posits that sensory systems are tuned to the regularities of their natural input. The statistics of natural image databases have been the topic of many studies, which have revealed biases in the distribution of orientations that are related to neural representations as well as behavior in psychophysical tasks. However, commonly used natural image databases contain images taken with a camera with a planar image sensor and limited field of view. Thus, these images do not incorporate the physical properties of the visual system and its active use reflecting body and eye movements. Here, we investigate quantitatively, whether the active use of the visual system influences image statistics across the visual field by simulating visual behaviors in an avatar in a naturalistic virtual environment. Images with a field of view of 120° were generated during exploration of a virtual forest environment both for a human and cat avatar. The physical properties of the visual system were taken into account by projecting the images onto idealized retinas according to models of the eyes' geometrical optics. Crucially, different active gaze behaviors were simulated to obtain image ensembles that allow investigating the consequences of active visual behaviors on the statistics of the input to the visual system. In the central visual field, the statistics of the virtual images matched photographic images regarding their power spectra and a bias in edge orientations toward cardinal directions. At larger eccentricities, the cardinal bias was superimposed with a gradually increasing radial bias. The strength of this effect depends on the active visual behavior and the physical properties of the eye. There were also significant differences between the upper and lower visual field, which became stronger depending on how the environment was actively sampled. Taken together, the results show that quantitatively relating natural image statistics to neural representations and psychophysical behavior requires not only to take the structure of the environment into account, but also the physical properties of the visual system, and its active use in behavior.
高效编码假说认为，感觉系统会根据其天然输入的规律进行调整。自然图像数据库的统计数据一直是许多研究的主题，这些研究揭示了与神经表征以及心理物理学任务中的行为相关的方向分布偏差。然而，常用的自然图像数据库包含使用具有平面图像传感器和有限视野的相机拍摄的图像。因此，这些图像没有纳入视觉系统的物理特性及其反映身体和眼睛运动的主动使用情况。在这里，我们通过在自然主义虚拟环境中模拟虚拟角色的视觉行为，定量研究视觉系统的主动使用是否会影响整个视野的图像统计。在探索虚拟森林环境时，为人类和猫的虚拟角色生成了视野为120°的图像。根据眼睛几何光学模型将图像投影到理想化视网膜上，从而考虑了视觉系统的物理特性。至关重要的是，模拟了不同的主动注视行为以获得图像集合，从而能够研究主动视觉行为对视觉系统输入统计的影响。在中央视野中，虚拟图像的统计数据在功率谱以及边缘方向朝向基本方向的偏差方面与摄影图像相匹配。在更大的偏心度下，基本偏差与逐渐增加的径向偏差叠加。这种效应的强度取决于主动视觉行为和眼睛的物理特性。上下视野之间也存在显著差异，这种差异会根据对环境的主动采样方式而变得更加明显。综上所述，结果表明，要将自然图像统计与神经表征和心理物理行为进行定量关联，不仅需要考虑环境结构，还需要考虑视觉系统的物理特性及其在行为中的主动使用情况。
