Scientists Help Explain Visual System Remarkable Ability to Recognize Complex Objects

How is it possible for a human eye to figure out letters that are twisted and looped in crazy directions, like those in the little security test internet users are often given on websites?
It seems easy to us—-the human brain just does it. But the apparent simplicity of this task is an illusion. The task is actually so complex, no one has been able to write computer code that translates these distorted letters the same way that neural networks can. That’s why this test, called a CAPTCHA, is used to distinguish a human response from computer bots that try to steal sensitive information.
Now, a team of neuroscientists at the Salk Institute for Biological Studies has taken on the challenge of exploring how the brain accomplishes this remarkable task. Two studies published within days of each other demonstrate how complex a visual task decoding a CAPTCHA, or any image made of simple and intricate elements, actually is to the brain.
The findings of the two studies, published June 19 in Neuron and June 24 in the Proceedings of the National Academy of Sciences (PNAS), take two important steps forward in understanding vision, and rewrite what was believed to be established science. The results show that what neuroscientists thought they knew about one piece of the puzzle was too simple to be true.
Their deep and detailed research—-involving recordings from hundreds of neurons—-may also have future clinical and practical implications, says the study’s senior co-authors, Salk neuroscientists Tatyana Sharpee and John Reynolds.
"Understanding how the brain creates a visual image can help humans whose brains are malfunctioning in various different ways—-such as people who have lost the ability to see,"