After some re-reading, I now understand in a way I didn't quite internalize before that stimulating the vagus nerve affects the amygdala. That is -- and I'm sure nothing is this simple -- in theory a problem with the vagus nerve could cause --- would cause, I think -- problems with whatever the amygdala does. The study reported on in this article seems to establish that pretty well. So ... I guess problems with the vagus nerve really might lead to problems involving dilation of the puils, for example. In fact, it appears that epinephrine does have SOMETHING to do with dilation of the pupils. (see this, for example.) And epinephrine does have SOMETHING to do with the vagus nerve:
"The research solves the mystery of how the adrenal gland could stimulate the release of norepinephrine in the brain, observers say. During stress, the adrenal medulla (near the kidneys) in humans and rats releases epinephrine into the bloodstream, famously causing the "fight-or-flight" response in the heart, lungs, stomach and elsewhere. However, epinephrine can't cross the blood-brain barrier. So what is the switch that turns on epinephrine? The vagus nerve."
-- Adelson, Stimulating the vagus nerve: memories are made of this
Wow this stuff is mind-bogglingly complicated. adrenal medulla? blood-brain barrier? afferent vs. efferent nerve fibers?
I think it's going to take a while to really parse through this stuff.
Thoughts on Newtown
4 years ago