The neural basis for perceptual grouping operations in the human visual system, including the processes which generate illusory contours, is fundamental to understanding human vision. We have employed functional magnetic resonance imaging to investigate these processes noninvasively. Images were acquired on a GE Signa 1.5T scanner equipped for echo planar imaging with an in-plane resolution of 1.5 x 1.5 mm and slice thicknesses of 3.0 or 5.0 mm. Visual stimuli included nonaligned inducers (pacmen) that created no perceptual contours, similar inducers at the corners of a Kanizsa square that created illusory contours, and a real square formed by continuous contours. Multiple contiguous axial slices were acquired during baseline, visual stimulation, and poststimulation periods. Activated regions were identified by a multistage statistical analysis of the activation for each volume element sampled and were compared across conditions. Specific brain regions were activated in extrastriate cortex when the illusory contours were perceived but not during conditions when the illusory contours were absent. These unique regions were found primarily in the right hemisphere for all four subjects and demonstrate that specific brain regions are activated during the kind of perceptual grouping operations involved in illusory contour perception.
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机译:人类视觉系统中感知分组操作的神经基础,包括产生虚幻轮廓的过程,是理解人类视觉的基础。我们已经采用功能磁共振成像来无创地研究这些过程。在配备有用于回波平面成像的GE Signa 1.5T扫描仪上获取图像,其平面内分辨率为1.5 x 1.5 mm,切片厚度为3.0或5.0 mm。视觉刺激包括不产生感官轮廓的不对齐的诱导物(pacmen),在Kanizsa正方形的角上产生虚幻轮廓的相似诱导物,以及由连续轮廓形成的真实正方形。在基线,视觉刺激和刺激后期间获取了多个连续的轴向切片。通过对每个采样的体积元素的活化进行多阶段统计分析,确定活化区域,并在各种条件下进行比较。当觉察到虚幻的轮廓时,特定的大脑区域被激活在外皮层中,而在没有虚幻的轮廓的情况下则未被激活。这些独特的区域主要在所有四个对象的右半球发现,并证明特定的大脑区域在涉及虚幻轮廓感知的感知分组操作中被激活。
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