Object, face, body and scene representations in the human brain

这项研究的目的是了解我们是如何看到我们所看到的：大脑如何分析落在眼睛视网膜上的光线，以编码一个充满物体、人和事物的世界？ 在过去的一年里，我们专注于复杂视觉刺激的感知，特别是真实世界的视觉场景(议定书93-M-0170，NCT00001360)。 对真实世界场景的感知： 现实世界的场景极其复杂和多种多样，但我们能够毫不费力地对它们进行识别和分类。虽然之前的研究已经确定了几个似乎专门负责场景处理的大脑区域，但这些不同区域的确切作用以及它们包含的信息仍然不清楚。 在过去几年提出的视觉处理的一般框架的基础上，我们一直在研究这三个场景选择区域的基本视觉属性，并试图了解这三个区域是如何在功能上相互作用的。特别是，我们一直在研究视网膜复制(将视野逐点映射到大脑皮层)和类别选择性(对不同视觉类别的图像，如场景和人脸的不同反应)之间的关系。我们通过将场景片段呈现到视野的特定部分，并使用功能磁共振测量整个大脑的反应来评估视网膜复制。同样，我们通过呈现不同类别(如人脸、场景、物体、身体)的图像并测量相关的反应来衡量类别选择性。我们发现，这两个不同的组织原则之间没有简单的关系。类别选择区域表现出视网膜复制，但与视网膜定位图没有简单的关系，单个类别选择区域与多个地图重叠。这些结果表明，单个类别选择性区域可能包含特定视网膜定位图中的多个子区域，这些子区域对图像执行单独的计算。 其中一个场景选择区域位于内侧顶叶皮质，通常与记忆功能有关。我们的数据显示，内侧顶叶皮质可能存在功能梯度。后部区域表现出很强的视网膜性和场景选择性，并且与后部视觉皮质的其他区域联系最强。相比之下，前部区域的视网膜视觉和场景选择性要小得多，但与与记忆有关的腹侧颞叶皮质和顶叶皮质区域显示出很强的连通性。 总而言之，这些结果提供了对参与处理真实世界视觉场景的大脑网络的重要见解。我们目前正在通过使用经颅磁刺激(TMS)暂时扰乱这些区域的功能并观察其对行为的影响来评估这些区域的特定作用。 阐明大脑如何使我们能够识别物体、场景、面孔和身体，有助于我们深入了解我们对周围世界的内在表征的本质。理解这些表征对于试图确定许多精神健康和神经疾病的潜在缺陷至关重要。

The goal of this research is to understand how we see what we see: how does the brain analyze the light falling on the retina of the eye to encode a world full of objects, people and things? During the past year we have focused on the perception of complex visual stimuli, in particular real-world visual scenes (Protocol 93-M-0170, NCT00001360). Perception of real world scenes: Real-world scenes are incredibly complex and heterogeneous, yet we are able to identify and categorize them effortlessly. While prior studies have identified several brain regions that appear to be specialized for scene processing, it remains unclear exactly what the precise roles of these different regions are and what information they contain. Building on a general framework for visual processing we proposed in the past few years, we have been investigating the basic visual properties of the three scene-selective regions and trying to understand how these three regions interact functionally. In particular, we have been investigating the relationship between retinotopy (point-by-point mapping of the visual field onto the cortex) and category-selectivity (differential responses to images from different visual categories e.g. scenes versus faces). We evaluate retinotopy by presenting fragments of scenes to specific portions of the visual field and measuring the response across the brain with fMRI. Similarly, we measure category-selectivity by presenting images from different categories (e.g. faces, scenes, objects, bodies) and measuring the associated response. We find that there is no simple relationship between these two different organizational principles. Category-selective regions exhibit retinotopy, but there is no simple relationship with the retinotopic maps and individual category-selective regions overlap multiple maps. These results suggests that individual category-selective regions may contain multiple sub-regions within specific retinotopic maps that perform separate computations on the images. One of these scene-selective regions is found in medial parietal cortex and is often implicated in memory functions. Our data show that there may be a gradient of function within medial parietal cortex. Posterior regions show strong retinotopy and scene-selectivity and are most strong connected with other regions of posterior visual cortex. In contrast anterior regions are much less retinotopic and scene-slective but show strong connectivity with regions of ventral temporal cortex and parietal cortex that are implicated in memory. Collectively these results provide important insights into the brain network that is involved in processing real-world visual scenes. We are currently evaluating the specific roles of these regions by using transcranial magnetic stimulation (or TMS) to temporarily disrupt their function and observe the impact on behavior. Elucidating how the brain enables us to recognize objects, scenes, faces and bodies provides important insights into the nature of our internal representations of the world around us. Understanding these representations is vital in trying to determine the underlying deficits in many mental health and neurological disorders.