Neural correlates of shape perception : neuroimaging studies.

本研究旨在通过神经成像技术阐明知觉情境效应的神经关联。我们研究了被试在视觉刺激加工过程中感受到不同背景效应时视觉皮层视网膜区域的脑活动，以及这些区域在视觉刺激加工过程中的功能关系。我们对背景效应的视觉现象进行了fMRI测量。我们在使用相位编码刺激的fMRI测量的基础上识别视网膜定位区域。测量受试者在感觉到色觉诱导、掩蔽和波动性完成时的脑活动，并对结果进行分析和比较。结果表明，早期和高级视觉皮层脑区活动的时空特征存在差异。一般而言，对于V1、V2和V3等早期过程，语境效应的空间范围被描述为局部的。另一方面，对于V4这样的较高阶段，语境效应的空间范围具有全局性。对色觉诱导和掩蔽效应的心理物理测量表明，视觉情境的差异效应对应于视觉信息的局部和全局加工。

The present study aimed to elucidate the neural correlates to the perceptual contextual effects by using neuroimaging technique. We examined the brain activities in the retinotopic areas of the visual cortex during subjects perceived the various stimuli evoking contextual effects and the functional relationship among these areas in the processing of the visual stimuli.We have carried out fMRI measurements for the visual phenomena of the contextual effects such as chromatic induction effect, masking effect and amodal completion. We identified the retinotopic areas on the basis of the fMRI measurement using phase-encoding stimuli. The brain activities were measured during subject perceived the chromatic induction, masking, and amodal completion and the results were analyzed and compared among the retinotopic areas. The results showed that there was difference in the spatio-temporal characteristics of the brain activities between the early and higher-order visual cortical areas. In general, the spatial extent of the contextual effect is characterized as local for early processes such as V1, V2 and V3. On the other hand, the spatial extent of the contextual effect is characterized as global for higher-stage such as V4. Psychophysical measurement of the chromatic induction and masking effect showed that the differential effects of the visual context correspond to the local and global processing of the visual information.