The role of area V4 in the perception and recognition of visual objects

 描述（由申请人提供）：人类视觉系统将到达我们眼睛的信息解析为区域和对象的有意义的排列。这个过程被称为图像分割，是灵长类动物大脑完成的最具挑战性的计算之一。为了揭示其神经基础，我们将研究猕猴两个脑区的神经元过程--V4和前额叶皮层（PFC）。V4是形态加工的基本阶段，沿着枕-颞通路，PFC对执行控制很重要。这两个领域的功能障碍损害形状歧视行为的显示器，需要识别分割的对象，强烈表明它们是重要的图像分割。我们的实验技术将包括单电极和多电极记录，行为操纵，微扰方法和计算机模型。在目标1中，我们将识别反映视觉皮层分割的神经信号。使用各种参数的刺激与闭塞，杂波和阴影刺激功能，挑战分割在自然视觉，我们将评估是否实现分割通过分组区域具有相似的表面特性，如表面颜色，纹理和深度，或通过分组轮廓段，可能形成一个对象的边界或这两种策略之间的一些相互作用。我们将测试的假设，轮廓分组机制是最有效的低杂波和接近中央凹。在目标2中，我们将研究PFC的反馈如何调节V4中的形状反应并促进分割：我们将测试长期存在的假设，即高级皮质阶段的物体识别先于视觉形式处理的中级阶段并促进分割。我们将同时研究V4和PFC神经元的群体，而动物从事形状辨别行为。我们将使用单次尝试解码方法和相关性分析，在这两个领域的神经元反应的内容和时间。为了从因果关系上测试PFC反馈的作用，我们将通过冷却可逆地抑制PFC并研究V4神经元。我们的研究结果将提供第一个详细的，分析模型的V4神经元响应动力学的存在下的闭塞和混乱，并推进我们的理解复杂的视觉场景是如何处理在V4区。他们还将揭示V4和PFC如何共同介导复杂形状辨别任务的表现，执行功能和中级视觉在行为过程中如何协调，以及反馈如何用于皮层计算。视觉失认症（一种枕-颞通路功能障碍）和PFC功能障碍（例如精神分裂症）会损害物体识别。这些实验的结果将构成我们对分割和对象识别基础的大脑计算的理解的重大进步，并将使我们更接近于设计策略来缓解和治疗这些能力受损的大脑疾病。

 DESCRIPTION (provided by applicant): The human visual system parses the information that reaches our eyes into a meaningful arrangement of regions and objects. This process, called image segmentation, is one of the most challenging computations accomplished by the primate brain. To discover its neural basis we will study neuronal processes in two brain areas in the macaque monkey-V4, a fundamental stage of form processing along the occipito-temporal pathway, and the prefrontal cortex (PFC), important for executive control. Dysfunctions of both areas impair shape discrimination behavior in displays that require the identification of segmented objects, strongly suggesting that they are important for image segmentation. Our experimental techniques will include single and multielectrode recordings, behavioral manipulations, perturbation methods and computer models. In Aim 1 we will identify the neural signals that reflect segmentation in visual cortex. Using a variety of parametric stimuli with occlusion, clutter and shadows-stimulus features known to challenge segmentation in natural vision-we will evaluate whether segmentation is achieved by grouping regions with similar surface properties, such as surface color, texture and depth, or by grouping contour segments that are likely to form the boundary of an object or some interplay between these two strategies. We will test the hypothesis that contour grouping mechanisms are most effective under low clutter and close to the fovea. In Aim 2, we will investigate how feedback from PFC modulates shape responses in V4 and facilitates segmentation: we will test the longstanding hypothesis that object recognition in higher cortical stages precedes and facilitates segmentation in the midlevels of visual form processing. We will simultaneously study populations of V4 and PFC neurons while animals engage in shape discrimination behavior. We will use single-trial decoding methods and correlation analyses to relate the content and timing of neuronal responses in the two areas. To causally test the role of feedback from PFC, we will reversibly inactivate PFC by cooling and study V4 neurons. Our results will provide the first detailed, analytical models of V4 neuronal response dynamics in the presence of occlusion and clutter and advance our understanding of how complex visual scenes are processed in area V4. They will also reveal how V4 and PFC together mediate performance on a complex shape discrimination task, how executive function and midlevel vision may be coordinated during behavior and how feedback is used in cortical computation. Object recognition is impaired in visual agnosia, a dysfunction of the occipito-temporal pathway, and in dysfunctions of the PFC (e.g. schizophrenia). Results from these experiments will constitute a major advance in our understanding of the brain computations that underlie segmentation and object recognition and will bring us closer to devising strategies to alleviate and treat brain disorders in which these capacities are impaired.