'Blindsight'

You wouldn’t believe your own eyes especially if you have read the background. The man on the video walked along a path strewn with obstacles — two trash cans, a tripod, a pile of papers, a desk organizer and a box. The hallway was deliberately littered with these objects to see if he could negotiate the walk without tripping or bumping into any of them. That would not have been such a big deal; not unless you know that the man who walked the path was clinically blind. He neither had a cane nor prior knowledge of the layout of the hall. I found myself rooting for him as I watched.

You can even watch the clip yourself at www.beatricedegelder.com/books.html. The video is part of the documentation of the study entitled Intact navigation skills after bilateral loss of striate cortex by Beatrice de Gelder, Marco Tamietto, Geert van Boxtel, Rainer Goebel, Arash Sahraie, Jan van den Stock, Bernard M.C. Stienen, Lawrence Weiskrantz and Alan Pegna. It appeared in the journal Current Biology. Beatrice de Gelder, who led the study, is a neuroscientist at Harvard and Tilburg University in the Netherlands.

The subject, named in the study only as TN, had his face blocked in the video. He is a doctor and was said to be initially very reluctant to participate in the study and of course, was very surprised when he was told that he perfectly scored in his navigation skills. His blindness was due to two successive strokes. His brain scan “showed a severe loss of posterior callosal fibers connecting the two occipital lobes” which essentially means that no input from his eyes would be able to register in his consciousness as images. So how could he have avoided the objects in the hall?

The researchers think that the clue may be in how TN performed in a previous test where he responded to facial images which he could not see. For example, he cringed when “shown” images of fearful faces. The researchers called this “blindsight” as they watched TN’s amygdala get activated when he was shown “emotional expressions of fear, anger and joy compared to neutral.” The team recorded his response in terms of TN’s behavior and through evidence gleaned from his electroencephalogram and brain scans.

There is nothing wrong with TN’s eyes except that the brain part that processes the images that the eyes send to it has been completely damaged. But it seems that the signals from our eyes also go to other parts of our brains, other than the part that gives us the “picture.” TN is clinically blind but scientists think that this case demonstrates that there are other ways other than the primary visual cortex in humans that “can sustain sophisticated visuo-spatial skills in the absence of perceptual awareness.” The researchers think that the signals from the eyes register in parts of the brain that somehow are able to still make sense of it — such as that of the amygdala for emotions and that part that the scientists called “border cells” which activate when we are near a wall or a barrier. At least, that was what it seemed like in rats and in a monkey named Helen mentioned in their other studies, as TN’s was the first human case where this was demonstrated.

Together with another recent study that found that the facial expressions are innate and not learned by observing others, these studies point us to the insight that there is a lot more to learning than just by “seeing” images. This other study involved looking at almost 5000 photographs of sighted and blind athletes (blind from birth) in their moments of triumph or disappointment. This study will appear in the Journal of Personality and Social Psychology that will come out this month and reported in Livescience last Dec. 29 by Jeanna Bryner. In the studied photos, the universal sad face seems to be one with “a downturned mouth and a raising of the inner eyebrow.”

I think another evidence, though not as direct, that facial expressions are innate, is found in the universal appeal of emoticons in terms of communicating with others, despite differences in culture. How we show what we feel are hardwired in the grays and whites in each of our mission control, and need not wait until we are taught how to let the world know when we grieve or when we rejoice.

Helen Keller was one of the most famous among the blind who walked the world in the most extraordinary way, with such artistry, eloquence and wisdom. She, too, was blinded most likely by meningitis as a child, which caused damage to parts of her brain that affected her sight and speech. She said, “It is a terrible thing to see and have no vision.” She knew she had a way of knowing — an access to that “vision,” even without “images” fed from her eyes. I wonder how she would have responded to this new finding as science has started to unravel the possible explanation for the rich tapestry of life she keenly perceived.

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