I'm not going to comment on epilepsy because I'm not a physician or a medical researcher. To me, epilepsy seems too powerful and independently energised by local neuronal activity to be overridden by a voluntary thought directed at the vagus nerve.

The examples the author gives of experienced meditators being able to influence what in non-practitioners are autonomic systems, makes sense, given that there is evidence for example of Tibetan monks surviving freezing temperatures. The investigations into that phenomenon show the physiological mechanism is to burn a particular type of fat. How do the monks access that physiology? The meditation switches it on. How does that work? That's the interesting part. It takes many years to learn and decades to gain the skills, but can be stated in one simple sentence. They use visualisation.

I learned to suppress sneezing after much practice. I don't have the language to describe the technique, but I go almost to the point of sneezing, doing the inhale, and then I sort of meditate. I neither try hard to stop the sneeze or do anything active - I just let my mind go blank, and set my expectations that the sneeze is going to fade away. And it does.