Mechanism of Rapid Object Recognition in Human Ventral Temporal Cortex

描述（由申请人提供）： 视觉系统执行的最具挑战性的任务之一是快速准确地识别视觉相似的物体。这对于识别个人面孔尤其重要，因为细微的差异在行为上至关重要。一方面，人脸识别是高度精确的，因为它需要区分非常相似的视觉刺激。另一方面，它是灵活的，因为我们可以毫不费力地快速识别特定的面孔，尽管其视网膜图像有相当大的变化。不知何故，面部识别（以及其他特定物体的识别）的皮层机制同时既严格又宽容。我们对人类大脑如何识别人脸和其他物体的详细了解大多来自血氧水平依赖（BOLD）功能性磁共振成像（fMRI）。特别是，功能磁共振成像已经在颞叶皮层的腹侧部分确定了一个特定的区域，即梭状面孔区（FFA），它对面孔的反应比对任何其他类别的视觉对象的反应都要强烈得多。尽管它的名字，FFA在识别面孔中的确切作用还不清楚，部分原因是FFA的神经活动和BOLD功能磁共振成像信号之间的间接关系。为了直接测量FFA中的神经活动，我们的实验将使用植入患者体内的电极进行癫痫的临床评价。这些方法提供了一个独特而安全的机会，以一种不可能的方式直接记录人类皮层的电生理。虽然FFA对人脸的BOLD反应一般大于对其他物体的反应，但FFA对不同人脸的反应是相似的，这可能是因为BOLD反应平均了许多神经元在空间和时间上的反应。然而，使用直接记录活动的FFA，我们将确定是否刺激诱发的局部场电位记录FFA在单次试验中可以区分两个不同的面孔。PI还将使用这些记录来确定FFA中的神经活动是否是我们识别人脸的能力的基础，尽管人脸的大小和位置不同。最后，我们将测试是否FFA是关键的判断面孔身份。神经元群体对行为的重要性的一个关键测试是在逐个试验的基础上其活动和行为表现之间的联系。我们将研究FFA活性和行为之间的相关性，在个体试验中，受试者识别变形的面孔。这些相关性将提供有力的证据，FFA参与个人面孔的歧视。拟议的实验研究神经科学中的一个基本问题（人类视觉感知的神经基础是什么？）这也是临床相关的。视知觉障碍是由于创伤和中风而导致的后天性脑损伤受害者的常见且显著的认知缺陷，这反过来又是当今美国退伍军人面临的主要问题。更好地了解视觉对象是如何在人类大脑中处理，可能会提供重要的见解，这些致残性损伤的病理生理学和康复。

DESCRIPTION (provided by applicant): One of the most challenging tasks performed by our visual system is the rapid and accurate identification of visually similar objects. This is particularly important for recognition of individual faces, where subtle differences are behaviorally crucial. On one hand, face recognition is highly precise, as it entails discrimination of very similar visual stimuli. On the other hand, it is flexible, as we can effortlessly and rapidly recognize a specific face in spite of considerable variations in its retinal image. Somehow, the cortical mechanisms that underlie face recognition (as well as recognition of other specific objects) are simultaneously both strict and tolerant. Most of our detailed knowledge about how the human brain recognizes faces and other objects comes from blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI). In particular, fMRI has identified a specific area in the ventral part of the temporal cortex, the fusiform face area (FFA) that responds much more strongly to faces than to any other category of visual object. Despite its name, the precise role of the FFA in recognizing faces is unclear, partly because of the indirect relationship between neural activity in the FFA and the BOLD fMRI signal. To allow for direct measurement of neural activity in the FFA, our experiments will be conducted using electrodes implanted in patients for the clinical evaluation of epilepsy. These implantations offer a unique and safe opportunity to directly record electrophysiological from human cortex in a way that is otherwise not possible. Although the BOLD response in the FFA to faces in general is greater than the response to other objects, the response in FFA to different individual faces is similar, likely because the BOLD response averages the response of many neurons over space and time. However, using direct recording of activity in the FFA, we will determine if stimulus-evoked local field potentials recorded from FFA in single trials can discriminate between two different faces. The PI will also use these recordings to determine if neural activity in the FFA underlies our ability to recognize a face in spite of variations in its size and position. Finally, we will test whether that the FFA is critical to judgments about face identity. A key test of the importance of a neuronal population for behavior is the connection between its activity and behavioral performance on a trial-by-trial basis. We will examine correlations between FFA activity and behavior across individual trials as a subject recognizes morphed faces. These correlations would provide powerful evidence that FFA is involved in discrimination of individual faces. The proposed experiments examine a fundamental question in neuroscience (what is the neural basis of human visual perception?) that is also clinically relevant. Impairments in visual perception are a frequent and significant cognitive deficit in victims of acquired brain injuries due to trauma and stroke, which in turn are major problems facing U.S. veterans today. A better understanding of how visual objects are processed in the human brain may provide important insights into the pathophysiology and rehabilitation of these disabling impairments.