Karnath H O, Ferber S, Bülthoff H H
Department of Cognitive Neurology, University of Tübingen, Hoppe-Seyler-Str 3, 72076 Tübingen, Germany.
Neuropsychologia. 2000;38(9):1235-41. doi: 10.1016/s0028-3932(00)00043-9.
The dissociation between object identity and object orientation observed in six patients with brain damage, has been taken as evidence for a view-invariant model of object recognition. However, there was also some indication that these patients were not generally agnosic for object orientation but were able to gain access to at least some information about objects' canonical upright. We studied a new case (KB) with spared knowledge of object identity and impaired perception of object orientation using a forced choice paradigm to contrast directly the patient's ability to perceive objects' canonical upright vs non-upright orientations. We presented 2D-pictures of objects with unambiguous canonical upright orientations in four different orientations (0 degrees, -90 degrees, +90 degrees, 180 degrees ). KB showed no impairment in identifying letters, objects, animals, or faces irrespective of their given orientation. Also, her knowledge of upright orientation of stimuli was perfectly preserved. In sharp contrast, KB was not able to judge the orientation when the stimuli were presented in a non-upright orientation. The findings give further support for a distributed view-based representation of objects in which neurons become tuned to the features present in certain views of an object. Since we see more upright than inverted animals and familiar objects, the statistics of these images leads to a larger number of neurons tuned for objects in an upright orientation. We suppose that probably for this reason KB's knowledge of upright orientation was found to be more robust against neuronal damage than knowledge of other orientations.
在六名脑损伤患者中观察到的物体识别与物体方向之间的分离，已被视为物体识别视图不变模型的证据。然而，也有一些迹象表明，这些患者并非普遍对物体方向失认，而是能够获取至少一些关于物体标准直立方向的信息。我们研究了一个新病例（KB），该患者物体识别知识保留，但物体方向感知受损，我们使用强制选择范式直接对比患者感知物体标准直立方向与非直立方向的能力。我们展示了具有明确标准直立方向的物体的二维图片，图片呈现四种不同方向（0度、-90度、+90度、180度）。无论给定方向如何，KB在识别字母、物体、动物或面部方面均无损伤。此外，她对刺激物直立方向的知识保存完好。形成鲜明对比的是，当刺激物以非直立方向呈现时，KB无法判断其方向。这些发现进一步支持了基于分布式视图的物体表征，其中神经元会针对物体特定视图中呈现的特征进行调谐。由于我们看到直立的动物和熟悉物体比倒立的更多，这些图像的统计数据导致更多神经元针对直立方向的物体进行调谐。我们推测，可能正是由于这个原因，发现KB对直立方向的知识比对其他方向的知识更能抵抗神经元损伤。
