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Johns Hopkins UniversityArts and Sciences Magazine

[RESEARCH BRIEF]

Decoding the Mysteries of Touch

Bennett and students

Hsiao's team found that neurons that can respond to touch can understand the orientation of bars pressed against the skin.

Neuroscientist Steven Hsiao, scientific director of the Zanvyl Krieger Mind/Brain Institute, isn't satisfied that a prosthetic limb simply allows its user to move. He wants users to feel what the artificial limb is touching—such as the texture and shape of a quarter, or the comforting perception of holding hands. Accomplishing these goals requires understanding how the brain processes the multitude of sensations that come in daily through our fingers and hands.

Using a $600,000 grant administered through the federal stimulus act, Hsiao is leading a team that is working to decode those sensations, which could lead to the development of truly "bionic" hands and arms that use sensitive electronics to activate neurons in the touch centers of the cerebral cortex.

"It is still a huge mystery how we humans use our hands to move about in the world and interact with our environment," says Hsiao. "How we reach into our pockets and grab our car keys or some change without looking requires that the brain analyze the inputs from our hands and extract information about the size, shape, and texture of objects. How the brain accomplishes this amazing feat is what we want to find out and understand."

Hsiao hypothesizes that our brains do this by transforming the inputs from receptors in our fingers and hands into "neural code" that the brain then matches against a stored central "databank" of memories of those objects. When a match occurs, the brain is able to perceive and recognize what the hand is feeling, experiencing, and doing.

In recent studies, Hsiao's team found that neurons in the area of the brain that respond to touch are able to "code for" (understand) orientation of bars pressed against the skin, the speed and direction of motion, and curved edges of objects. Now Hsiao's team will investigate the detailed neural codes for more complex shapes, and will delve into how the perception of motion in the visual system is integrated with the perception of tactile motion.

"The practical goal of all of this is to find ways to restore normal sensory function to patients whose hands have been damaged, or to amputees with prosthetic or robotic arms and hands," Hsiao says.