FUNCTIONAL BRAIN IMAGING STUDIES OF HUMAN VISUAL COGNITION

人类神经系统介导的视觉感知，注意和记忆在完整的大脑功能成像研究。功能磁共振成像（fMRI）用于精确测量与选定的视觉感知和记忆任务的表现相关的局部血流动力学变化。这些血流动力学变化是局部神经活动变化的指标。人和猕猴一样，人类的外层视觉皮层被组织成腹侧物体视觉流和背侧空间视觉流。腹侧物体视觉通路被发现有一个功能结构，它对面孔和不同类别的物体（如房子、椅子、动物和工具）产生不同的反应模式。这些与类别相关的反应模式在受试者之间非常一致。研究发现，面部感知涉及颞叶腹侧皮层和颞上沟，前者更多地参与对面部身份的表征，后者更多地参与对面部结构的可变方面的表征，这些方面对社会交流很重要，如表情和眼睛注视的方向。完整的物体和空间视觉加工流，包括脑后外皮层和前额叶投射，参与物体和空间视觉工作记忆。不同的前额叶区域与物体和空间视觉工作记忆有关。空间工作记忆激活了额上沟的一个区域，该区域正好位于人的额视野前部。三是在解剖和功能上分别确定了参与物体工作记忆的额中回和额下回前额叶区域。事件相关的功能磁共振成像被用来区分工作记忆中跟踪项目的互补机制——一个用于跟踪重复的项目以促进忽略干扰物，另一个用于跟踪工作记忆搜索的目标。

Human neural systems that mediate visual perception, attention, and memory were investigated in the intact brain with functional brain imaging. Functional magnetic resonance imaging (fMRI) was used to measure precisely localized hemodynamic changes associated with the performance of selected visual perceptual and mnemonic tasks. These hemodynamic changes are indices of local changes in neural activity. Human extrastriate visual cortex, like that of the macaque monkey, is organized into a ventral object vision stream and a dorsal spatial vision stream. The ventral object vision pathway was found to have a functional architecture that produces different patterns of response for faces and different categories of objects, such as houses, chairs, animals, and tools. These category-related patterns of response are remarkably consistent across subjects. Face perception was found to involve both the ventral temporal cortex, which is more involved in the representation of face identity, and the superior temporal sulcus, which is more involved in the representation of changeable aspects of the facial configuration that are important for social communincation, such as expression and eye gaze direction. The complete object and spatial visual processing streams, including posterior extrastriate and prefrontal projections, participate in object and spatial visual working memory. Different prefrontal areas were associated with object and spatial visual working memory. Spatial working memory activated a region in the superior frontal sulcus just anterior to the human frontal eye field. Three, anatomically and functionally distinct prefrontal regions in the middle and inferior frontal gyri were identified that participate in object working memory. Event-related fMRI was used to distinguish complementary mechanisms for tracking items in working memory - one for tracking repetitions of items to facilitate ignoring distracters and one for tracking the target of a working memory search.