LOCALIZING OBJECTS IN DYNAMIC SCENES

描述(申请人提供)：大多数视觉和视觉运动功能取决于我们的视觉系统在动态场景中定位物体的能力--当我们移动或当世界上的物体在我们周围移动时确定物体的位置。然而，动态定位要求视觉系统必须能够分配和更新对象位置，目前还不清楚哪些视觉区域扮演这些必要的角色，以及什么机制负责。考虑到眼睛很少稳定，而且物体在移动时不断地在视网膜上漂移，分配和更新物体的位置尤其相关。鉴于视觉处理的迟缓特性，我们如何清晰和精确地感知运动对象的位置？为了理解视觉系统如何分配和更新物体位置，我们必须将定位任务视为一个动态过程，而不是一个静态过程。我们提出的实验的目标是描述在动态情况下决定知觉位置的神经路径和机制。我们的初步结果表明，当视网膜上存在运动时，需要两种机制来感知物体的位置：后缘去模糊和边缘移位。如果没有这些机制，我们会认为世界是一个模糊的污点，无法准确预测物体未来的位置，也无法在它们在我们周围移动时与它们互动。我们假设这两个独立的机制整合了早期视觉区域(V1)和运动敏感区域(MT)之间的信息。我们的实验数据表明：(1)MT携带关于物体位置的精确信息，支持它在物体定位中起着不可或缺的作用的假设；(2)当存在视网膜运动时，V1和MT之间的反馈和前馈连接可能是分配和更新物体位置所必需的。利用功能磁共振成像(FMRI)、经颅磁刺激(TMS)和心理物理学，我们将描述和分离这两种机制的神经轨迹，并确定它们在感知物体位置中的因果作用。动态定位是视觉系统面临的默认情况，但许多神经系统疾病在动态视觉和视觉运动定位方面会产生特定的缺陷，包括视性共济失调、阅读困难、运动障碍、自闭症和精神分裂症等。在我们了解如何在正常大脑中确定不断在视网膜上移动的图像的位置之前，我们缺乏必要的洞察力来开发这些损伤的诊断工具、预测标记和治疗方法。

DESCRIPTION (provided by applicant): Most visual and visuomotor functions hinge on our visual system's ability to localize objects in dynamic scenes-to determine the positions of objects as we move or as objects in the world move around us. However, dynamic localization requires that the visual system must be able to both assign and update object positions, and it remains unclear which visual areas play these necessary roles and what mechanisms are responsible. Assigning and updating object locations is especially relevant considering that the eye is rarely stabilized and objects are constantly drifting across the retina as they move. Given the sluggish nature of visual processing, how do we perceive the positions of moving objects with clarity and precision? To understand how the visual system assigns and updates object positions, we must approach the task of localization not as a static process, but as a dynamic one. The goal of our proposed experiments is to characterize the neural pathways and mechanisms that determine perceived position in dynamic situations. Our preliminary results suggest that two mechanisms are required to perceive the positions of objects when motion is present on the retina: trailing edge deblurring and edge-shifting. Without these mechanisms, we would perceive the world as a blurry smear, unable to accurately predict the future locations of objects or interact with them as they move around us. We hypothesize that these two independent mechanisms integrate information between early visual areas (V1) and the motion sensitive region (MT+). Our pilot data for the proposed experiments suggest that (1) MT+ carries precise information about object position, supporting the hypothesis that it serves an integral role in object localization, and (2) feedback as well as feed-forward connections between V1 and MT+ may be necessary to assign and update the positions of objects when retinal motion is present. Using functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), and psychophysics, we will characterize and isolate the neural locus of the two mechanisms and establish their causal roles in perceiving object position. Dynamic localization is the default situation faced by the visual system, but many neurological disorders produce specific deficits in dynamic visual and visuomotor localization, including optic ataxia, dyslexia, akinetopsia, autism, and schizophrenia, among others. Until we understand how position is determined in the normal brain for images that are constantly moving across the retina, we lack the necessary insight to develop diagnostic tools, predictive markers, and therapies for these impairments.