Blindsight - History

History

Like so many other interesting phenomenon dealing with the brain, we owe much of our current understanding of blindsight to early experiments on monkeys. One monkey in particular, Helen, could be considered the “star monkey in visual research” because she was the original blindsight subject. Helen was a macaque monkey that had been decorticated; specifically, her primary visual cortex (V1) was completely removed. This procedure had the expected results that Helen became blind as indicated by the typical test results for blindness. Nevertheless, Helen, under certain specific situations, also exhibited sighted behavior. Her pupils would dilate, and she would blink at stimulus that threatened her eyes. Furthermore, it was discovered that under certain experimental conditions she could detect a variety of visual stimulus like the presence and location of objects; the truly amazing part was that she could also discriminate between shape, pattern, orientation, motion, and color! In many cases she was able to navigate her environment and interact with objects as if she was sighted.

A similar phenomenon was also discovered in humans. Subjects who had suffered damage to their visual cortices due to accidents or strokes reported partial or total blindness. Nevertheless, when prompted they could “guess” with above average results about the presence and details of objects much like the animal subjects. They could even catch objects tossed at them when prompted (“Catch!”) . Interestingly, the subjects never developed any kind of confidence in their abilities. Even when told of their successes they would not begin to spontaneously make “guesses” about objects but instead still required prompting. Furthermore, blindsight subjects rarely express the amazement about their abilities we sighted people would expect them to express.