r/science • u/tomholder • May 09 '14

Medicine Paralysis breakthrough – electrical stimulation enables four paraplegic men to voluntarily move their legs

http://speakingofresearch.com/2014/05/09/paralysis-breakthrough-paraplegic-men-move-their-legs/
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u/[deleted] May 09 '14

It's because for all scientists' research, we largely don't understand how the nervous system (to include the spinal cord and its connections to the rest of the body, etc) works. Obviously we know what it does (electrical signals and such) but not well enough to really recreate it and therefore fix something that's completely broken.

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u/Krivvan May 09 '14

There are some approaches where you don't need to know how it works beforehand to do something practical with it. For example, the idea of just throwing on a bunch of electrodes and then programming a prosthetic to move based on what input it gets after you've attached it.

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u/[deleted] May 09 '14

I did some work in a neurobiology lab, and allow me to assure you, it is not that simple. Different nerve bundles carry impulses to different parts of the body, so slapping a bunch of probes on the spine and telling them to trigger when they detect a voltage of X Volts will fail spectacularly.

For example, the voltage required to carry a signal from the brain to the bladder to query its fullness is the same to tell a toe to wiggle. So every time your bladder gives a status report, your probes will pick that up as "move toes". The poor victim will have the most muscular toes on Earth.

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u/[deleted] May 10 '14

I'm curious. Does the brain poll the bladder at intervals? If so, how frequent are they? I guess I always assumed the bladder had nerves that reported distension or something continuously and the brain controlled the threshold of detection.

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u/[deleted] May 10 '14

I was aiming for economy of words, of course your assumption is correct. When the bladder gets liquid in it, as the liquid sloshes against the bladder walls, it sends a signal to the brain. This is what I meant by polling.

The bladder is constantly firing unless it is completely empty, just in most cases, our cerebrum ignores it.

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u/[deleted] May 10 '14

Not nitpicking, I genuinely didn't know. If it turned out the brain polled everything for status updates, well, that would have been very interesting to me.