tips us to a story about a nationwide effort to incorporate advanced technology into the next generation of prosthetic arms
. Researchers for the DARPA-funded project are developing feedback techniques that range from sensors on the surface of the user's skin to electrodes implanted on the inside of the user's skull that intercept and interpret signals from the motor cortex. Quoting:
"'Think about taking a sip from a can of soda,' Harshbarger says. The complex neural feedback system connecting a native limb to its user lets that user ignore an entire series of complicated steps. The nervous system makes constant automatic adjustments to ensure, for example, that the tilt of the wrist adjusts to compensate for the changing fluid level inside the can. The action requires little to no attention. Not so for the wearer of current prosthetic arms, for whom the act of taking a sip of soda precludes any other activity. The wearer must first consciously direct the arm to extend it to the correct point in space, then switch modes to rotate the wrist into proper position. Then he must open the hand, close it to grasp the soda can (not so weakly as to drop it but not so hard as to crush it), switch modes to bend the elbow to correctly place the can in front of his mouth, rotate the wrist into position, and then concentrate on drinking from the can of soda without spilling it."