Self-Motion Perception Heads for Home

Article excerpt

As a person walks down a street or drives along a highway, features of the outside world appear to emerge from a point in the distance and stream by in a perceptual phenomenon that scientists appropriately call optical flow. Even walkers who glance up at cloud patterns and drivers who sneak peeks at roadside billboards manage, for the most part, to go with the optical flow and safely reach their destinations.

Keen eyesight certainly helps one to steer through space and avoid obstacles as the head tilts to and fro. But nerve impulses from neck muscles, the ear's inner canals, and other parts of the head must be given their due. They offer crucial navigational aid to people on the move, a new study finds.

As a traveler looks in various directions while moving toward a goal, vision combines with these sources of bodily information to keep him or her headed in the right direction, according to a team of neuroscientists led by James A. Crowell of the California Institute of Technology in Pasadena.

The ear's vestibular canals sense the angle and speed of head movements; muscle signals alert the brain to the neck's orientation relative to the body; and motor commands for head turns are relayed to the visual system. Accurate estimates of a person's approach to a destination require access to at least two of these three nonvisual information sources, the researchers say.

Their report, published in the December Nature Neuroscience, supports theories that cognitive functions reflect an interplay of brain, body, and environment. …