They said people who used a video-game training program saw significant improvements in their ability to notice subtle differences in shades of gray, a finding that may help people who have trouble with night driving.

"Normally, improving contrast sensitivity means getting glasses or eye surgery -- somehow changing the optics of the eye," said Daphne Bavelier of the University of Rochester in New York, whose study appears in the journal Nature Neuroscience.

"But we've found that action video games train the brain to process the existing visual information more efficiently, and the improvements last for months after game play stopped."