The case of Michael May, the blind man who can now "see" gives us a fascinating instance of the mind-brain conundrum and how habits shape perception.
May was blinded in both eyes at the age of three by an explosion of calcium carbide. The jar of powder he had placed in water produced a gas which was accidentally ignited by a spark from a nearby incinerator. He narrowly escaped death. After six months in hospital, he emerged with only light and bright colour perception and then lost total sight in his left eye as a teenager. A series of early cornea transplants failed.
Then in 1999, May underwent a pioneering epithelial stem-cell transplant of new tissue to replace damaged scar tissue. This was followed some four months later by the transplant of a donated cornea. The next day, when bandages were removed, May could see colours and objects hundreds of feet away.
The problem for him was and remains interpreting what is seen, making sense of shapes and colours, let alone shapes and colours in motion. After two years of sight, May, once a fine blind skier, still can't ski easily with his eyes open. Nor can he recognise his wife until she speaks. Although he has very good "optical acuity", he can't process what he sees or, as he says, "catalogue" it. His visual language is growing slowly, but it is still a foreign language.
May's case disproves the notion that we can see independently of conceptual frameworks. Seeing things over and over - that is learning - somehow gives us frameworks through which to interpret sensation from then on.
The way May experiences "sight" also throws light on our models of the brain. One of the standard models, borrowed from the computer world, would be that we're born hard-wired (brain) with the ability or not to run certain programmes (mind). Michael May was born with the hard-wiring for seeing, but somewhere along the way that hard- wiring was altered by the altered workings of his mind.
The day-to-day running of life, we could say, reshaped his hardwiring. Seeing was no longer there, and the new programme put in place by years of blindness reprogrammed the hard-disk.
One of the many things I learned in shadowing neuroscientists for a year is that the older notions that discrete parts of the brain engage in narrowly discrete functions - sight, speech and so on - are moving quickly past their sell-by date. At its simplest level, seeing may be merely the registering of light and reacting to it. When we move into the complexities of perception and recognition, which also involve memory and a lifetime of habit, much more than the visual cortex comes into play.
At its …