fMRI and Behavioral Analyses of the Representation of Shape

在几分之一秒的时间里，一个物体或场景的图像——一个以前从未经历过的——可以很容易地被人类观察者理解。功能性磁共振成像（fMRI）对这一非凡壮举的神经基础的研究已经得到了极大的推进，因为发现了一个皮层区域，它对完整的物体反应良好，但对这些相同图像的混乱版本却没有反应。这个区域被称为“外侧枕复合体”（LOC），从枕叶腹侧延伸到颞叶后部。LOC不仅被熟悉的对象激活，在不熟悉的对象（如抽象雕塑）中，LOC也比它们的混乱版本产生更大的激活。LOC的激活也不仅仅是早期视觉阶段的前馈效应，因为与完整的图像版本相比，这些阶段对打乱的图像显示出更大的激活。LOC对同一物体的照片和线条画的反应是相同的。双侧LOC病变已被证明会导致完全无法根据物体形状识别物体，而视觉引导的运动相互作用则不受影响。因此，LOC表示物理形状，可能与语义信息（包括名称）相关联。因此，这个阶段看来是在认识的开端。尽管LOC本地化器实现了一些进步，但是这个本地化器实际本地化的内容仍然存在相当大的不确定性。置乱操作既影响图像的低级测量，也影响与对象解释相关的高级方面。低水平的测量包括由元素散射产生的显示范围的增加，低频信息的损失，以及团块从一个（完整的对象）明显增加到超过20个。当然，随着散射，团块的大小也同样减小。在美国国家科学基金会（National Science Foundation）的资助下，欧文·比德曼博士将进行功能磁共振成像（fMRI）研究，旨在弄清定位器定位的究竟是什么，并在此过程中为如何从图像中提取形状提供一些线索。该研究将阐明物体与纹理的神经编码，显示中元素数量的影响以及这些元素是否构成完整的物体或场景。此外，将注意定义那些可能对某些方面更敏感的皮质区域，如纹理而不是物体，在混乱的图像中。直接的更广泛的影响将有助于推进我们的知识，形状的神经表征的目的是识别。这项研究将填补物体识别的心理物理（行为）研究和猕猴形状变化的单单元记录之间的关键空白。虽然人类和猕猴的初级感觉和运动皮层的同源性已经很好地建立起来，但关于后期感知“关联”区域的同源性仍然存在重大问题。广泛的计划已经到位，包括南加州大学的nsf资助的3T扫描仪。由于实时对象识别问题对非技术高级受众的可访问性，本研究将成为向南加州大学主要少数民族社区的学生展示认知神经科学的特色研究项目之一，并招募一些人参与研究本身。

In a fraction of a second, an image of an object or scene--one never experienced previously--can be easily comprehended by a human observer. The functional magnetic resonance imaging (fMRI) study of the neural basis of this remarkable feat has been greatly advanced by the discovery of a cortical area that responds well to intact objects but not to scrambled versions of these same images. This region, termed "the lateral occipital complex" (LOC), runs ventrally from the occipital lobe to the posterior regions of the temporal lobe. LOC is not merely activated by familiar objects in that unfamiliar objects, such as abstract sculptures, also produced greater activation in LOC compared to their scrambled versions. Nor is activation in LOC merely a feed forward effect from earlier visual stages in that these stages show greater activation for the scrambled compared to the intact versions of the images. LOC responds equivalently to a photograph and a line drawing of the same object. Bilateral lesions to LOC have been shown to produce a complete inability to recognize objects on the basis of their shape, while leaving visually guided motor interactions unaffected. LOC thus represents physical shape to which, presumably, semantic information, including a name, can be associated. This stage thus appears to be at the threshold of cognition. Despite the advances enabled by the LOC localizer, there is considerable uncertainty as what this localizer is actually localizing. The scrambling operation affects both low-level measures of the image as well as higher-level aspects associated with the interpretation of the object. The low-level measures include an increase in the extent of the display produced by the scattering of the elements, a loss of low frequency information, and a marked increase in the clumps from one (the intact object) to over 20. Of course, with the scattering, the sizes of the clumps are similarly reduced. With National Science Foundation funding, Dr. Irving Biederman will conduct fMRI research designed to clarify just what the localizer is localizing and in doing so, provide some clues as to how shape is abstracted from an image. The research would elucidate the neural coding of object vs. texture, the effect of the number of elements in a display and whether these elements comprise an intact object or scene. Additionally, attention will be paid toward defining those cortical areas that might be more responsive to aspects, such as texture rather than object, in the scrambled images.The immediate broader impacts will be to contribute to advancing our knowledge as to the neural representation of shape for purposes of recognition. The research will fill a critical gap between psychophysical (behavioral) research on object recognition and single-unit recording of shape variations in the macaque. Although the homologues between human and macaque of primary sensory and motor cortices are well established there are significant questions concerning the homologues of later, perceptual "association" areas. Extensive plans are already in place for an outreach program involving USC's NSF-funded 3T scanner. Because of the accessibility of the problem of real-time object recognition to a non-technically advanced audience, this research will be one of the featured research projects for exposing cognitive neuroscience to students from USC's largely minority neighborhood and to recruit some to participate in the research itself.