Your Brain Can Sees What You Can't

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blindsight.jpg

One of the most interesting phenomena that we discussed briefly about in Psy 1001 lecture is blindsight. Basically, it is when a "visually blinded" person can still detect an object and succeed in variety of discrimination tasks through guesswork but unaware that he can see it. Through some research, I discovered that people with blindsight are not only able to subconsciously use visual information to navigate, but they are also able to detect emotion and even gender of others. This rare phenomenon occurs when the patient's primary visual cortex, the region that considered essential to sight has been damaged due to injury or stroke. However, their visual system is still functioning fine: the visual information is going to the retina's visual receptors (rods and cones), and activating the higher visual cortex of the brain for visual processing. Researchers believe it is this disconnection of the primary visual pathway that disrupted the communication part of the visual processing that is causing the problem.
The first intensive case study on blindsight is DB, who is blind because of the surgical removal of a non-malignant tumor in his right visual cortex (V1) at the age of 33 years old. He is reported to be aware of basic shape and line in the discrimination task, although for him it is more of a guessing game throughout the procedure. When presented him with more complex images, DB was able to distinguish the image with one word syllable though many responses are not correct they clearly in similar category with the image. One theory for DB's phenomenon is that in the absence of V1, his visual processing skips through V1 and the visual input is then transfer to the dorsal pathway (the Where pathway) that identifying what things are without projecting the image in his brain through V1. There is a video clip on blindsight: http://www.youtube.com/watch?v=RuNDkcbq8PY (it is the same documentary that we watched about Phantom Limb)

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This page contains a single entry by voxxx114 published on October 9, 2011 1:14 PM.

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