How do you change your brain? How can you recover from a neurological injury such as a stroke or learn to see or hear in a new way? I've gathered a number of clues from my own experience in gaining stereovision as well as from talking with and reading about others. In the next several posts, I'll describe what I've learned. Here's the first tip:

You would not want your brain to rewire itself in response to every new occurrence or change in the environment. If this were the case, your sense of the world would be in constant flux. Thus, an adult brain is picky. While a very young brain may change in response to any stimulus that is presented with enough repetition, an older brain rewires itself primarily in response to behaviorally important stimuli.

This idea first became clear to scientists when they studied barn owls. These birds are amazing hunters, and they use both their eyes and ears to locate prey. In several experiments, scientists put prisms over both eyes of the owls so that their whole visual field was shifted many degrees to the right or left . With the prisms, the eyes told the birds that the mouse was in one place while the ears reported that the mouse was in another. Young owls automatically shifted their spatial auditory maps to match the prism-altered visual maps. This happened whether or not the owls hunted for their food or were caged and fed. In contrast, older owls who did not have to catch their food did not adjust. Only when forced to hunt did they realign their auditory maps with their visual ones. Connections in the brains of the older owls changed only when it was necessary to catch their prey, clearly a behaviorally important task.