

Research promises a more capable prosthetic limb







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RE: why couldn't they just read the signals?
By geddarkstorm on 11/15/2007 3:46:45 PM , Rating: 3
From all I understand, nerve signals aren't simply electronic. There is an action potential, but the real signal is sent by the type of neural transmitters a particular nerve is set up to release at a particular time (which is why drugs affect nerves--a drug isn't electrical, but it can mimic a neural transmitter and screwup all the signals in the brain). The action potential will be identical in either case that you want to relax or contract a muscle, it's just different nerves will be used, or the same nerve got a different nerve's signal and switched which neural transmitter it was shipping to the synapse. You can't just hook up an electrode to a nerve and have it make sense. This isn't even to mention the ratio of transmitters released, and the overall concentrations all cause slightly different outputs. Neural signaling is incredibly complex and more like analogue instead of digital; the action potential is only a "release what's been prepared" signal, not the signal itself.

So then, by simply watching the twitch initiated by the proper signals in the chest muscles, the processor can fine tune the specific movement, degree of movement, and so forth. There's a lot of translation that still has to go on, which is why it's a breakthrough in its own right. None the less, there's no way yet to make complete sense of a nerve impulse by itself as it can mean so many different things (some nerves are much easier to translate than others just by the degree and frequency of their action potentials; such as optical nerves which are committed to one signal so you don't have to worry so much about which neural transmitter is being use, but in general this is not the case); not till there are systems to detect neural transmitters and translate that correctly.

By Manch on 11/15/2007 8:26:30 PM , Rating: 2
Measuring the twitch of the muscle is used because measuring the contraction is far easier than decoding the nerves signal itself. Also measuring these is easy using a couple of leads.

The muscle acts as a sort of potentiometer. The electrical signal from the muscle can be measured using electromyography. They can measure Voltage and Frequency. Measuring these they can mimic to a degree how fast(frequency) how much force(voltage) etc.

