The comfort and pleasure of holding a hand, the warning that comes from grabbing the sharp edge of a knife, the coolness of silk as it runs through the fingers. All of these are examples of the sophisticated communication that goes on between the hands and the cerebral cortex. While a number of today’s prosthetic hands have earned the moniker “bionic,” with their fine motor control and life-like range of motion, scientists at Johns Hopkins University (JHU) now aim to provide such limbs with an additional, meaningful layer-the feeling associated with the sense of touch.
Photograph of Steven Hsiao, PhD, courtesy of Will Kirk, Homewood Photographic.
JHU neuroscientist Steven Hsiao, PhD, is leading a team of researchers who aim to provide prosthetic hands with sensitive electronics that will activate neurons in the touch sensors of the cerebral cortex, to “feel” what the hand is touching, thereby providing the warnings and pleasures associated with this powerful perception.
“The truth is, it is still a huge mystery how we humans use our hands to move about in the world and interact with our environment,” Hsiao said in a JHU press release. “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.”
The study is being funded by a $600,000 grant administered through the federal stimulus act and builds on several previous studies. In those studies, Hsiao’s team found that neurons in the area of the brain that respond to touch are able to “code for,” or understand, the orientation of bars pressed against the skin, the speed and direction of motion, and curved edges of objects. In their stimulus-funded study, 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 team will do this by first investigating how complex shapes are processed in the somatosensory cortex and second, by studying the responses of individual neurons in an area that has traditionally been associated with visual motion but appears to also have neurons that respond to 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 said. “I believe that these neural coding studies will provide a basic understanding of how signals should be fed back in to the brain to produce the rich percepts that we normally receive from our hands.”
