As the brain sorts through the mountains of visual stimuli that it encounters every day, it shines a spotlight on conveniently located objects that could serve as tools, a new study shows. It is the first evidence that a passing glimpse of mundane--but potentially useful--tools can seize the brain's attention as dramatically as flashing lights and sudden motion.
Stare directly at a screwdriver and the motor areas of your brain will get you ready to grasp it. But what about that hammer briefly spotted in the corner of your eye? Cognitive neuroscientist Todd Handy of Dartmouth College in Hanover, New Hampshire, and colleagues theorized that the brain's visual areas might check for graspable objects in peripheral vision in order to compute their location, size, and orientation, for example.
To test this idea, Handy's team used an electroencephalogram (EEG) to measure electrical activity in the occipital cortex, a visual area of the brain, as right-handed volunteers focused on the center of a computer screen. When tools appeared in the lower or right peripheral visual areas--where right-handed people most often grab objects--a blip in the EEG indicated that the occipital cortex was paying attention. Nothing happened at the sight of less useful items, such as a goat or a sailboat. Functional magnetic resonance imaging showed that motor areas responded most to tools in the same locations, suggesting that as the brain's motor system prepares to grasp a tool, it draws the visual system's attention to the object's location. The research is published online 17 March in Nature Neuroscience.
"It's a terrific paper," comments neuroscientist Melvyn Goodale of the University of Western Ontario in London, Ontario, adding to the little-researched area of how the brain uses visual information to guide action. Goodale wonders whether graspable objects that are not tools also capture visual attention. To examine that question, Handy's group is currently testing whether objects that not everyone would recognize as tools, such as the artificial hand-holds that rock climbers use for indoor climbing, also grab visual attention--and if so, whether they do so only for rock-climbers.
Todd Handy's Web site