UCL Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK.
Neuropsychologia. 2012 Jun;50(7):1393-407. doi: 10.1016/j.neuropsychologia.2012.02.024. Epub 2012 Mar 7.
Visual perception depends not only on local stimulus features but also on their relationship to the surrounding stimulus context, as evident in both local and contextual influences on figure-ground segmentation. Intermediate visual areas may play a role in such contextual influences, as we tested here by examining LG, a rare case of developmental visual agnosia. LG has no evident abnormality of brain structure and functional neuroimaging showed relatively normal V1 function, but his intermediate visual areas (V2/V3) function abnormally. We found that contextual influences on figure-ground organization were selectively disrupted in LG, while local sources of figure-ground influences were preserved. Effects of object knowledge and familiarity on figure-ground organization were also significantly diminished. Our results suggest that the mechanisms mediating contextual and familiarity influences on figure-ground organization are dissociable from those mediating local influences on figure-ground assignment. The disruption of contextual processing in intermediate visual areas may play a role in the substantial object recognition difficulties experienced by LG.
视觉感知不仅取决于局部刺激特征，还取决于它们与周围刺激环境的关系，这在图形-背景分割的局部和上下文影响中都很明显。中间视觉区域可能在这种上下文影响中发挥作用，我们在这里通过检查 LG 来测试这一点，LG 是一种罕见的发育性视觉失认症。LG 没有明显的大脑结构异常，功能神经影像学显示 V1 功能相对正常，但他的中间视觉区域（V2/V3）功能异常。我们发现，LG 中图形-背景组织的上下文影响被选择性地破坏，而图形-背景影响的局部来源则被保留。物体知识和熟悉度对图形-背景组织的影响也显著降低。我们的结果表明，介导图形-背景组织上下文和熟悉度影响的机制与介导图形-背景分配的局部影响的机制是可分离的。中间视觉区域中上下文处理的破坏可能在 LG 经历的大量物体识别困难中起作用。
