Mechanism of Rapid Object Recognition in Human Ventral Temporal Cortex

描述(由申请人提供)： 我们的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上相似的对象。这对于识别个人面孔尤其重要，因为细微的差异在行为上是至关重要的。一方面，人脸识别的精确度很高，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人脸，尽管它的视网膜图像有很大的变化。不知何故，面部识别(以及对其他特定物体的识别)背后的大脑皮层机制同时是严格和宽容的。我们关于人脑如何识别人脸和其他物体的大部分详细知识来自血氧水平依赖(BOLD)的功能磁共振成像(FMRI)。特别是，功能磁共振成像识别出了颞叶皮质腹侧部分的一个特定区域，即梭形面部区域(FFA)，它对人脸的反应比对任何其他类别的视觉对象都要强烈得多。尽管名为FFA，但FFA在识别人脸方面的确切作用尚不清楚，部分原因是FFA中的神经活动与大胆的fMRI信号之间存在间接关系。为了能够直接测量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临床评估癫痫。这些植入提供了一种独特而安全的机会，以一种其他方式不可能的方式直接记录人类大脑皮层的电生理。虽然FFA对面孔的大胆反应一般比对其他物体的反应更大，但FFA对不同个体面孔的反应是相似的，可能是因为大胆反应是许多神经元在空间和时间上的平均反应。然而，使用直接记录FFA中的活动，我们将确定在单个试验中从FFA记录的刺激诱发的局部场电位是否可以区分两个不同的脸。PI还将使用这些记录来确定FFA中的神经活动是否支持我们识别面孔的能力，尽管面孔的大小和位置不同。最后，我们将测试FFA是否对人脸身份的判断至关重要。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。我们将在个体试验中检查FFA活动和行为之间的相关性，因为受试者识别变形的脸。这些相关性将提供强有力的证据，表明FFA参与了对个人面孔的歧视。拟议中的实验考察了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？)这在临床上也是相关的。视觉感知障碍是由于创伤和中风而导致的后天性脑损伤患者经常出现的一种严重的认知缺陷，而这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在人脑中是如何处理的，可能会为这些致残损伤的病理生理学和康复提供重要的见解。 公共卫生相关性： 许多因头部创伤或中风而后天脑损伤的美国退伍军人，都失去了认知处理周围单词的能力。我们对大脑处理周围环境的能力知之甚少，目前也几乎没有什么办法来康复或治疗精神处理障碍的患者。我们的项目利用了一个独特的机会来直接观察人类大脑的活动，以研究大脑如何使我们能够识别特定的物体。更好地理解大脑是如何奇迹般地处理视觉信息的，最终应该会帮助我们更好地治疗大脑受伤的患者。

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. PUBLIC HEALTH RELEVANCE: Many of the U.S. veterans with acquired brain injuries due to head trauma or stroke suffer a loss in their ability to cognitively process the word around them. Little is know about the brain allows us to process our surroundings, and there is currently very little that can be done to rehabilitate or treat patients with disabling deficits in mental processing. Our project uses a unique opportunity to directly observe the human brain's activity in order to study how the brain enables us to recognize specific objects. A better understanding how the brain is miraculously able to process visual information should ultimately help us better treat patients with injured brains.