Neurobiology Department, Weizmann Institute of Science, Rehovot, Israel.
Department of Psychology, Sapienza University, Rome, Italy.
Sci Rep. 2017 Nov 1;7(1):14848. doi: 10.1038/s41598-017-13921-z.
Visual crowding is a perceptual phenomenon with far-reaching implications in both perceptual (e.g., object recognition and reading) and clinical (e.g., developmental dyslexia and visual agnosia) domains. Here, we combined event-related fMRI measurements and wide-field brain mapping methods to investigate whether the BOLD response evoked by visual crowding is modulated by different attentional conditions. Participants underwent two sessions of psychophysical training outside the scanner, and then fMRI BOLD activity was measured simultaneously in early visual areas (including the visual word form area, VWFA), while they viewed strongly-crowded and weakly-crowded Gabor patches in attended and unattended conditions. We found that crowding increased BOLD activity in a network of areas including V1, V2, V3A, V4/V8, and VWFA. In V4/V8 and VWFA we found an increased activity related to attention. The effect of crowding in V1 was recorded only when attention was fully devoted to the target location. Our results provide evidence that some area beyond V1 might be the likely candidate for the site of crowding, thus supporting the view of visual crowding as a mid-level visual phenomenon.
视觉拥挤是一种具有深远意义的知觉现象，在知觉（例如，物体识别和阅读）和临床（例如，发展性阅读障碍和视觉失认症）领域都有涉及。在这里，我们结合事件相关 fMRI 测量和广域脑映射方法，研究了视觉拥挤引起的 BOLD 反应是否受到不同注意力条件的调节。参与者在扫描仪外进行了两次心理物理训练，然后在注视和非注视条件下同时测量他们观看强拥挤和弱拥挤的 Gabor 补丁时早期视觉区域（包括视觉词形区 VWFA）的 fMRI BOLD 活动。我们发现，拥挤会增加包括 V1、V2、V3A、V4/V8 和 VWFA 在内的一系列区域的 BOLD 活动。在 V4/V8 和 VWFA 中，我们发现与注意力相关的活动增加。只有当注意力完全集中在目标位置时，V1 中的拥挤效应才会被记录下来。我们的结果提供了证据，表明 V1 以外的某些区域可能是拥挤的候选部位，从而支持视觉拥挤是一种中级视觉现象的观点。
