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.
Dr. Edward Taub and his colleagues work with patients who have lost the use of an arm following a stroke. They discovered that the patients who regained the most function in their arm were not the individuals who best performed the exercises in the therapist's office but rather those who regularly practiced using their affected arm in the routine tasks of daily life, such as brushing their teeth, combing their hair, or picking up a coffee cup. The brain rewires itself to complete behaviorally relevant tasks.
Similarly, for me to learn to see in 3D, I had to learn how to aim my two eyes at the same place in space at the same time. If I had tried to learn this only with the use of complicated pieces of equipment such as stereoscopes or computer programs, I may not have generalized these new skills to everyday life. Instead, I practiced aiming my eyes at targets in real space while moving in routine ways. Now, whenever I work out on a Nordic track or treadmill, I also practice my vision therapy exercises, thus giving my eyes, brain, and body a workout all at the same time. If I had learned how to see in stereo only while sitting still, I wouldn't be able to see in 3D for much of the time. Instead, I taught myself how to see in stereo for everyday activities, whether sitting quietly or moving about.
Note: You can read about my experiences in rehabilitating my vision and about brain plasticity in general in my book, Fixing My Gaze.