http://www.businessinsider.com/vagus-ne ... ion-2015-6
some highlights:
It is made of thousands and thousands of fibres and 80 per cent of them are sensory, meaning that the vagus nerve reports back to your brain what is going on in your organs.
Operating far below the level of our conscious minds, the vagus nerve is vital for keeping our bodies healthy. It is an essential part of the parasympathetic nervous system, which is responsible for calming organs after the stressed ‘fight-or-flight’ adrenaline response to danger. Not all vagus nerves are the same, however: some people have stronger vagus activity, which means their bodies can relax faster after a stress.
The strength of your vagus response is known as your vagal tone and it can be determined by using an electrocardiogram to measure heart rate. Every time you breathe in, your heart beats faster in order to speed the flow of oxygenated blood around your body. Breathe out and your heart rate slows.
Research shows that a high vagal tone makes your body better at regulating blood glucose levels, reducing the likelihood of diabetes, stroke and cardiovascular disease. Low vagal tone, however, has been associated with chronic inflammation.
One of the vagus nerve’s jobs is to reset the immune system and switch off production of proteins that fuel inflammation. Low vagal tone means this regulation is less effective and inflammation can become excessive,
Twin studies show that to a certain extent, vagal tone is genetically predetermined – some people are born luckier than others. But low vagal tone is more prevalent in those with certain lifestyles – people who do little exercise, for example.
Vagal tone was measured at the beginning of the experiment and at the end, nine weeks later. As part of the experiment, half of the participants were taught a meditation technique to promote feelings of goodwill towards themselves and others.
Those who meditated showed a significant rise in vagal tone, which was associated with reported increases in positive emotions. “That was the first experimental evidence that if you increased positive emotions and that led to increased social closeness, then vagal tone changed,” Kok says.