Wednesday, December 31, 2008

Blind man 'sees' a path

Reviewer: Liesel Deppe

Reference: Blind man 'sees' a path
Benedict Carey. The Globe and Mail. Toronto, Ont.: Dec 23, 2008. pg. A.2

Summary: This was a brief report I encountered in the Globe and Mail on December 23rd, 2008. The original study was published in the journal "Current Biology". The subject of this study was a doctor who was left blind by two successive strokes. In the experiment he was required to navigate an obstacle course without help. He did so successfully, managing to avoid a garbage can, a tripod and several other onbjects.

Review: Scientist have previously reported on cases of blind people with partial damage to their visual lobes. However, this is the first study to show that there is something else at work, since both visual lobes were destroyed in this patient; or in more technical terms: where there is an apparent total absence of a striate cortex(where visual processing takes place.)

This study seems to suggest that we have a sub-conscious visual system; one where we have the ability to sense things by using the brain's primitive, subcortical system.

This seems to suggest that there are various forms/ degrees of blindness. This experiment might not have worked one a patient who was born blind or on one who had damage to the ideas. In the experiment, the patient suffered from damage to the brain, not the eyes. This means that his eyes couls still see, but that the processing took place in a different region of the brain, as well as in a different fashion. To ensure that there was no activity in the cortex, researchers took brain scans and magnetic resonance images of the brain, making sure that nothing was actually happening. Researchers also ensured that the patient was not navigating by reflected sound - the way bats navigate.

The fact that our brains process information from our eyes using two sets of circuits is not a new revelation to researchers. Apparently, cells in the retina project to the visual cortex, as well as to the subcortical areas. These subcortical areas include the superior colliculus (crucial in eye movement; possibly in other sensory functions as well). It is also suspected that information is also sent through the amygdala, which registers emotion.

Response: I was able to locate some footage of the experiment, which can be viewed here:

This experiment seems to demonstrate the amazing capabilities of our brains - I think that we are actually not aware of how much it can do, or how it can adapt. It would be interesting to know what the role of light played in this experiment. Would he perphaps have been less successful had it been dark? This reminds me of a blind student I taught for a while. She was born blind and it was obvious from her eyes that she could not see. I was amazed at how well she navigated her apartment and how she was able to cook us a dinner without help. She did mention however that she could sense whether or not there was light in the room. Therefore, I think it would be interesting to experiment further with levels of light in the obstacle course.

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