Vagus Nerve and Neurostimulation
Neurostimulators being a type of neuroprosthetic that act to deliver data into the brain directly, they can be used for a plethora of purposes. Regulating the brain, regulating data from the body, replacing data from the body, even potentially replacing data from the body, and providing direct data feedback from a computer system. It is even conceivable that they could be used as part of a technological telepathy system, inputting the mental voice of person A into person B's head.
Stimulation of the vagus nerve is one usage that we already have for neurostimulators. The vagus nerve is one of the most critical body sensory and control nerves since it does not deal with the outer body, instead heading straight down into the organs of the torso.
It is also called the pneumogastric nerve since it innervates both the lungs and the stomach. In addition, it supplies parasympathetic nerves to the whole body - it controls the entire of the subconscious immune system.
It is also one of ten cranial nerves. That is to say, one of ten cranial nerve pairings which split out from the brain directly, rather than move through the central spinal cord. That means it travels down the neck into the body, independent of the main brainstem. This means it can be interfaced with directly, without altering the signals of the spinal nerves - which means a general pulse stimulator can be used. That is fortunate, as general pulse systems are all we have right now.
There are two nerves that makeup the vagus. As with every other major nerve, one goes down the left side of the body, one goes down the right. Typically the one on the left is the one to which the neurostimulator gets attached. This is because the left passage has few connections to the heart, whilst the right passage has many.
Previous attempts at stimulation of the vagus nerve on the right hand side produced heart rhythm abnormalities as the brain's instructions to the heart for how to beat and behave were scrambled. This was less than desirable, so now the left side is used.
The stimulators used currently tend to be to cure epilepsy, as it has been found that a regular pulse up and down the vagus nerve, lessens or cures epileptic fits. Likewise, it seems to lessen extreme depression. In both cases, no-one is really sure why this occurs, just that it does. Given that, many surgeons are happy to just run with it. Still, there is significant research into just how changing the data signals on the main inner body control nerves can have such an effect on epileptic fits.
We still, at this time, have little idea whatthe codes that pass along the vagus, actually are. We know what they do in a general manner, of course, just not what the individual codes are. Very little investigation has been done in this area thus far, and it looks to continue like this for the foreseeable future - the spinal nerves have the majority of research attention.