最近，一篇发表于Proceedings of the National Academy of Sciences USA杂志的研究报告中，西安大略大学的视觉神经学专家Chris Striemer等人解开了一个谜团：大脑是如何控制肢体避开障碍并准确地取到想要的事物。
在这项研究中，研究对象是一位因大脑主要视觉区域中风，导致左眼视力完全丧失但右眼正常的患者，研究人员要求其避开各种障碍获取其右视觉区的目标物。显然，他能成功地完成该测试。但令人吃惊地是，当障碍物转移到他的左边盲区，他依然能够避开障碍物。该患者的行为表明，他在完全不知道障碍物的情况下，对障碍物的位置也非常敏感。
这项发现证实了避障能力(obstacle avoidance)能绕开大脑内主要的视觉区域而依赖于大脑内原始的视觉通路。因此，即使我们大脑的视觉中心部分损伤，大脑的其他部分仍能保持有限的能力来利用眼睛获得的视觉信息来控制肢体的运动。
此外，研究人员还通过试验表明，这些原始的视觉通路仅能发挥功能是即时(real-time)的，并不能进入记忆系统。例如，在患者的盲区设置一个障碍物，但时间是在他拿到之前两秒钟，即使是在这么短的时间内，患者的行为表明他已对物体的位置不具有敏感性。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS September 2, 2009, doi: 10.1073/pnas.0905549106
“Real-time” obstacle avoidance in the absence of primary visual cortex
Christopher L. Striemer, Craig S. Chapman and Melvyn A. Goodale,1
Canadian Institutes of Health Research (CIHR) Group on Action and Perception, Centre for Brain and Mind, Department of Psychology, Social Sciences Centre, The University of Western Ontario, London, Ontario, Canada N6A 5C2
When we reach toward objects, we easily avoid potential obstacles located in the workspace. Previous studies suggest that obstacle avoidance relies on mechanisms in the dorsal visual stream in the posterior parietal cortex. One fundamental question that remains unanswered is where the visual inputs to these dorsal-stream mechanisms are coming from. Here, we provide compelling evidence that these mechanisms can operate in “real-time” without direct input from primary visual cortex (V1). In our first experiment, we used a reaching task to demonstrate that an individual with a dense left visual field hemianopia after damage to V1 remained strikingly sensitive to the position of unseen static obstacles placed in his blind field. Importantly, in a second experiment, we showed that his sensitivity to the same obstacles in his blind field was abolished when a short 2-s delay (without vision) was introduced before reach onset. These findings have far-reaching implications, not only for our understanding of the time constraints under which different visual pathways operate, but also in relation to how these seemingly “primitive” subcortical visual pathways can control complex everyday behavior without recourse to conscious vision.
