Although most people think that we see with our eyes, most of the hard work is actually performed by our brains. The eyes themselves simply transmit information, via nerve impulses generated in the retina, to the part of our brain at the back of our head devoted to “seeing”.
There isn’t just one area in the brain devoted to vision, but rather many areas that radiate towards the front of our brain. Visual information from the eyes first arrives in the brain at the primary visual cortex, which encodes simple characteristics about images such as edges or bars. This information is then passed on to higher cortical areas where more and more complex image properties are represented.
A simple analogy might be to consider how a cartoonist creates an illustration. He first draws outlines of characters and then adds in details and colour, rendering the illustration more and more complex with every iteration. The brain can be likened to working in a similar manner: early cortical areas do the easy work, while later areas are lumbered with increasingly complicated tasks.
Recent research suggests that the first stages of visual processing in the primary visual cortex mainly occur unconsciously, but we actually have no idea what the neurons that convey information about vision are doing. These areas contain a multitude of neurons – approximately 150 million in...
