Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands.
Neuropsychologia. 2011 Jan;49(1):138-46. doi: 10.1016/j.neuropsychologia.2010.11.006. Epub 2010 Nov 21.
Finger agnosia has been described as an inability to explicitly individuate between the fingers, which is possibly due to fused neural representations of these fingers. Hence, are patients with finger agnosia unable to keep tactile information perceived over several fingers separate? Here, we tested a finger agnosic patient (GO) on two tasks that measured the ability to keep tactile information simultaneously perceived by individual fingers separate. In experiment 1 GO performed a haptic search task, in which a target (the absence of a protruded line) needed to be identified among distracters (protruded lines). The lines were presented simultaneously to the fingertips of both hands. Similarly to the controls, her reaction time decreased when her fingers were aligned as compared to when her fingers were stretched and in an unaligned position. This suggests that she can keep tactile input from different fingers separate. In experiment two, GO was required to judge the position of a target tactile stimulus to the index finger, relatively to a reference tactile stimulus to the middle finger, both in fingers uncrossed and crossed position. GO was able to indicate the relative position of the target stimulus as well as healthy controls, which indicates that she was able to keep tactile information perceived by two neighbouring fingers separate. Interestingly, GO performed better as compared to the healthy controls in the finger crossed condition. Together, these results suggest the GO is able to implicitly distinguish between tactile information perceived by multiple fingers. We therefore conclude that finger agnosia is not caused by minor disruptions of low-level somatosensory processing. These findings further underpin the idea of a selective impaired higher order body representation restricted to the fingers as underlying cause of finger agnosia.
手指失认症被描述为无法明确区分手指，这可能是由于这些手指的神经表示融合所致。因此，手指失认症患者是否无法将多个手指同时感知到的触觉信息分开？在这里，我们对一位手指失认症患者（GO）进行了两项任务的测试，这两项任务都衡量了将单个手指同时感知到的触觉信息分开的能力。在实验 1 中，GO 执行了一个触觉搜索任务，其中需要在分散注意力的物体（突起的线）中识别目标（不存在突起的线）。这些线同时呈现于双手的指尖。与对照组一样，当她的手指对齐时，她的反应时间比手指伸展且未对齐时要短。这表明她可以将来自不同手指的触觉输入分开。在实验 2 中，GO 需要判断食指的目标触觉刺激相对于中指的参考触觉刺激的位置，无论手指是否交叉。GO 能够像健康对照组一样指示目标刺激的相对位置，这表明她能够将两个相邻手指同时感知到的触觉信息分开。有趣的是，与健康对照组相比，GO 在手指交叉的情况下表现更好。总的来说，这些结果表明 GO 能够隐式地区分多个手指感知到的触觉信息。因此，我们得出结论，手指失认症不是由低级感觉处理的轻微干扰引起的。这些发现进一步支持了这样一种观点，即手指失认症是手指特定的高级身体表示受损的选择性障碍，是手指失认症的根本原因。
