Perception of Material and Texture in Vision and Action

有大量的研究是关于视觉系统如何处理形状和形状的。然而，对于物体属性（如表面纹理）是如何被感知系统处理的，我们所知甚少，表面纹理表明了重要的材料属性（如粗糙度或柔软度）。这是令人惊讶的，因为我们的感知系统很容易识别这些属性，但同样令人惊讶的是，我们的许多行为决定，我们如何抓住或与物体互动，取决于对物质属性的准确感知。人体成像研究表明，腹侧流中的特定区域与处理形状、形状和颜色的区域不同，负责纹理识别（can, Arnott, & Goodale, 2009）。然而，尚不清楚哪些视觉信息用于估计材料的粗糙度或柔软度。最近，Giesel和Zaidi（2013）提出，视觉系统使用与材料的3D结构相关的单目/基于图像的线索来估计图像中的粗糙度。综上所述，这提出了几个有趣的问题：1)视觉系统如何决定2D和3D刺激的材料特性是否存在差异；2)如何使用材料属性的感知估计来通知视觉运动系统，反之亦然？3)视觉运动系统如何利用材料属性来相应地调整其动作？为了解决这些问题，我们将使用一系列技术，包括行为到达和抓取研究，感知评级，材料特性的计算分析和神经心理学。在感知实验中，已知与纹理感知粗糙度相关的参数（即凸起的高度、密度、锐度和尖度）将在2D和3D刺激中独立和系统地变化，对感知系统的影响将在心理物理实验中测量。在视觉运动实验中，关于纹理的视觉和触觉信息将通过镜子分离，这样参与者就可以抓住一个物体（放在镜子后面），这个物体的感觉与他们看到的物体（放在镜子前面）不同（例如更粗糙或更光滑）。物体属性的感知估计将在物体交互之前和之后进行评估。这将使我们能够确定物质感知是否会随着触觉体验而改变。这一点很重要，因为目前对于视觉是否以及触觉体验在多大程度上影响视觉或反之亦然知之甚少。此外，计划进行一项神经心理学研究，以调查患有腹侧静脉损伤的患者是否能够识别形状和形状，但在区分不同纹理和颜色方面没有问题（Cavina-Pratesi, Kentridge, Heywood, & Milner, 2009），能够确定粗糙和柔软纹理等材料特性。如果这些估计，如建议的那样，依赖于从图像线索推断3D结构（与形式有关），那么患者应该无法识别特定的材料属性，例如对于不熟悉的刺激，柔软或粗糙，即使纹理辨别仍然是可能的。总之，这些实验将提供对感知和视觉运动系统使用哪些线索来估计材料特性以及这些信息如何在人脑中处理的更多理解。

There is a vast amount of research on how the visual system processes form and shape. However, much less is known about how object properties, such as surface texture, that indicate important material properties (eg its roughness or softness), are processed by the perceptual system. This is surprising because our perceptual systems recognise these properties with ease, but also surprising because many of our behavioural decisions, how we grasp or interact with an object, depend on the accurate perception of material properties.Human imaging studies have shown that specific areas within the ventral stream, that are distinct from those processing shape, form and colour, are responsible for texture discrimination (Cant, Arnott, & Goodale, 2009). Yet, it is unknown which visual information is used to estimate the roughness or softness of a material. Recently, Giesel and Zaidi (2013) suggested that the visual system estimates roughness in pictures using monocular/image based cues which are related to the 3D structure of the material. Taken together, this raises several interesting questions: 1) Are there any differences in how the visual system determines material properties for 2D and 3D stimuli; 2) How is the perceptual estimation of material properties used to inform the visuomotor system and vice versa? and 3) How does the visuomotor system use material properties to adapt its actions accordingly?To address these questions, we will use a range of techniques, including behavioural reaching and grasping studies, perceptual ratings, computational analysis of material properties and neuropsychology. In the perceptual experiments, parameters that are known to relate to the perceived roughness of a texture (ie height, density, sharpness and pointedness of the bumps) will be varied independently and systematically in both 2D and 3D stimuli and the effects on the perceptual system will be measured in psychophysical experiments. In the visuomotor experiments, the visual and haptic information about texture will be dissociated using a mirror setup such that participants grasp an object (placed behind a mirror) that feels different (eg rougher or smoother) than the object they see (placed in front of a mirror). Perceptual estimates of object properties will be assessed prior to and after object interactions. This will allow us to determine whether material perceptions change depending on the haptic experience. This is important as currently little is known about if and to what extent vision is affected by tactile experience or vice versa. In addition, a neuropsychological study is planned to investigate if a patient with ventral stream damage that is known to be unable to perceive shape and form but has no problems discriminating between different textures and colours (Cavina-Pratesi, Kentridge, Heywood, & Milner, 2009), is able to determine material properties such as rough and soft textures. If these estimations, as suggested, rely on inferring 3D structure (relating to form) from pictorial cues, the patient should be unable to identify specific material properties such as soft or rough for unfamiliar stimuli even when texture discrimination is still possible. Together these experiments will provide an increased understanding of which cues the perceptual and visuomotor system use to estimate material properties and how this information is processed in the human brain.