fMRI and Behavioral Analyses of the Representation of Shape

在不到一秒钟的时间内，人类观察者可以很容易地理解一个物体或场景的图像--一个以前从未经历过的图像。功能磁共振成像(FMRI)对这一非凡壮举的神经基础的研究得到了极大的进步，因为发现了一个皮质区域，该区域对完整的物体反应良好，但对这些图像的混乱版本不起作用。这一区域被称为“枕侧复合体”(LOC)，从枕叶腹侧至颞叶后部。LOC不仅被熟悉的物体激活，因为与它们的混乱版本相比，不熟悉的物体，如抽象雕塑，也在LOC中产生更大的激活。LOC中的激活也不仅仅是来自早期视觉阶段的前馈效应，因为与图像的完整版本相比，这些阶段对加扰的图像显示出更大的激活。LoC对同一对象的照片和线条画的响应是相同的。双侧病变到LOC已被证明完全不能根据物体的形状识别物体，而视觉引导的运动相互作用不受影响。因此，LoC表示物理形状，推测包括名称在内的语义信息可以关联到该物理形状。因此，这一阶段似乎处于认识的门槛。尽管LOC本地化程序实现了这些改进，但该本地化程序实际本地化的内容仍存在相当大的不确定性。加扰操作影响图像的低级别测量以及与对象的解释相关联的较高级别方面。低水平措施包括由元素的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)显著增加到超过20个。当然，随着散射，团块的大小类似地减小。在国家科学基金会的资助下，欧文·比德曼博士将进行功能磁共振研究，旨在澄清定位器正在定位的是什么，并在这样做的过程中，提供一些关于如何从图像中提取形状的线索。这项研究将阐明物体与纹理的神经编码，显示器中元素数量的影响，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方面更敏感的皮质区域，如纹理而不是物体，在置乱的图像中。直接的更广泛的影响将有助于促进我们对形状的神经表征的知识，以便识别。这项研究将填补关于物体识别的心理物理(行为)研究和单一单位记录猕猴形状变化之间的关键空白。虽然人类和猕猴之间初级感觉和运动皮质的同源已经被很好地建立起来，但关于后来的知觉“联系”区域的同源仍然存在重大问题。涉及南加州大学国家科学基金会资助的3T扫描仪的外展项目已经有了广泛的计划。由于实时物体识别问题对非技术先进的受众来说很容易理解，这项研究将成为向南加州大学以少数族裔为主的社区的学生展示认知神经科学并招募一些人参与研究本身的特色研究项目之一。

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.