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"Manhattan Project" For Prosthetic Arms
cortex 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."
I think the only thing we really need to do to improve the arms is creating more inputs. You could have the equivalent of a switch(that senses muscle signals) placed on different parts of the body that would be connected directly to the different motors. You wouldn't need any fancy computer to read brain signals to determine that the user wants pick up a glass and calculate the necessary movements to do this. I think of this like the controls on heavy machinery. The levers directly control the cylinders, and even though they may have little relationship to the actual direction of movement of the end effector, people can operate them effectively. I know this was my experience after a couple of hours using a mini excavator (which is super fun BTW). You don't even think about it anymore. It feels like the machine is part of your body and it just does what you want it to.
I'm thinking of something like a series of pads on the leg muscles like the ones they use now on the shoulder that can tell basic gross signals like raising and lowering the shoulder to open or close the claw. One for each motor. They would normally be off, but turned on when the use wanted to move his arm. The only draw back I see with this is that marathon runners trying to drink during the race could have unpredictable results.