College of Optometry, University of Houston, Houston, TX, USA.
School of Optometry, Vision Science Graduate Group, Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, USA.
Sci Rep. 2018 Jun 15;8(1):9177. doi: 10.1038/s41598-018-27480-4.
Crowding is the substantial interference of neighboring items on target identification. Crowding with letter stimuli has been studied primarily in the visual periphery, with conflicting results for foveal stimuli. While a cortical locus for peripheral crowding is well established (with a large spatial extent up to half of the target eccentricity), disentangling the contributing factors in the fovea is more challenging due to optical limitations. Here, we used adaptive optics (AO) to overcome ocular aberrations and employed high-resolution stimuli to precisely characterize foveal lateral interactions with high-contrast letters flanked by letters. Crowding was present, with a maximal edge-to-edge interference zone of 0.75-1.3 minutes at typical unflanked performance levels. In agreement with earlier foveal contour interaction studies, performance was non-monotonic, revealing a recovery effect with proximal flankers. Modeling revealed that the deleterious effects of flankers can be described by a single function across stimulus sizes when the degradation is expressed as a reduction in sensitivity (expressed in Z-score units). The recovery, however, did not follow this pattern, likely reflecting a separate mechanism. Additional analysis reconciles multiple results from the literature, including the observed scale invariance of center-to-center spacing, as well as the size independence of edge-to-edge spacing.
拥挤是指目标识别过程中相邻项目的实质性干扰。人们主要在视觉外围研究了带有字母刺激的拥挤现象，而针对中央凹刺激的研究结果则相互矛盾。虽然已经确定了外围拥挤的皮质位置（其空间范围很大，可达目标偏心距的一半），但由于光学限制，更难以分离中央凹的影响因素。在这里，我们使用自适应光学（AO）克服了眼像差，并采用高分辨率刺激来精确描述具有高对比度字母的中央凹横向相互作用，这些字母两侧是字母。存在拥挤现象，在典型的未受干扰的性能水平下，最大边缘到边缘干扰区为 0.75-1.3 分钟。与早期的中央凹轮廓相互作用研究一致，性能是非单调的，近端侧翼存在恢复效应。建模表明，当退化表现为灵敏度降低（以 Z 分数单位表示）时，可以用单个函数来描述侧翼的有害影响，而恢复则不符合这种模式，这可能反映了一种单独的机制。进一步的分析调和了文献中的多个结果，包括观察到的中心到中心间距的尺度不变性，以及边缘到边缘间距的尺寸独立性。
