After suffering a stroke that damaged right-brain tissue, including the primary visual cortex, a 68-year-old college professor could no longer see most objects on his left side. Then, under the supervision of Krista Schendel and Lynn C. Robertson, both of the Veterans Affairs Northern California Health Care System in Martinez, the professor literally reached out to recapture some of his lost sight.
His vision improved markedly when he extended his left arm toward computer-displayed items positioned within reach on his blind side, Schendel and Robertson report in the July-Aug. Journal of Cognitive Neuroscience. This is the first evidence that a well-placed arm can partly reverse vision loss following an injury to the brain’s visual hub.
The man—called WM in the report—used his right hand to press a key when he saw a blue circle flash at various locations on a computer’s screen. He detected most circles on the screen’s right side but only 14 percent of circles on the left side. When WM extended his left arm toward the screen, he again detected most right-side circles, but his success at detecting circles on the left side shot up to 25 percent.
In a set of tests where the circles appeared on an out-of-reach surface, WM exhibited no vision gains when he extended his left arm toward the circles. However, if he held a tennis racket, putting the circles within reach, he showed almost as much vision recovery as he did in the first set of tests.
Neurons outside the visual cortex that respond both to the feel of objects and to sights near an observer’s body may have fostered WM’s ability to see more when activated by arm movement, the scientists theorize. So far, such neurons have been found only in monkeys.