Why the Blind Cannot See When Given Eyes

The family and medical staff who attended Vincent, blinded since childhood by thick cataracts, had high hopes that, for the first time in nearly 45 years, he would be able to see following a surgery to remove the cataracts. When the bandages came off, Vincent saw colors, movement and shape. He even saw details and isolated features of objects. What he could not do, to their dismay, was to make sense of what he saw: he could not form coherent perceptions of objects in his world from the parts and features, and he had no sense of space, depth, or distance. (1)

That Vincent could perceive color, motion and shape directly following surgery is not surprising, given that the eye comes equipped to transduce signals relating to color, motion and shape. (2)These signals leave the eye, converging and diverging along neural pathways to other visual processing centers in the brain. (3) Eventually, many end up at the occipto-temporal region, which is specialized for object recognition, and the posterior parietal area, which is specialized for spatial perception. Interestingly, Vincent's pattern of impairment seems to roughly correspond to these "what" and "where" processes in the brain. (8) What interests me mainly is the failure of Vincent's "what" process, his inability to organize the various percepts into meaningful, whole representations. (4)

Early in the 20th century, Gestalt psychologists explored how organization governs perception by grouping parts into coherent wholes. They discovered laws of grouping, including similarity, proximity, good continuation, and closure. (5) From his pattern of visual perceptive deficits, it appears that Vincent's brain does not group visual input into wholes according to the Gestalt principles. The visual stimulus remains fragmented, disorganized. If there is a center in the brain for perceiving objects (like the "what center"), is it somehow related to the Gestalt-like integration of objects into wholes? And if so, how does that mechanism work, and why does it not seem to work for Vincent?

Unfortunately, although the Gestalt principles did predict with great accuracy how objects tend to be perceptually grouped as wholes, it was mainly a descriptive theory. It didn't try to link the observed regularities with biological substrates or explain how the phenomena arose. It could be that the brain comes equipped with Gestalt-like mechanisms (such as a bias to group pieces into a whole based on how much relative space is between the pieces - the principle of "proximity").