Dr. Jack Feldman

and actually move that air out, this group of cells, which is silent at rest, suddenly becomes active to drive those muscles.

And it appears that it's an independent oscillator in a region around the facial nucleus.

When this region was initially identified,

We thought it was involved in sensing carbon dioxide.

It was what we call a central chemoreceptor.

That is, we want to keep carbon dioxide levels, particularly in the brain, at a relatively stable level because the brain is extraordinarily sensitive to changes in pH.

if there's a big shift in carbon dioxide, there'll be a big shift in brain pH, and that'll throw your brain, if I can use the technical term, out of whack.

And so you want to regulate that.

And the way to regulate something in the brain is you have a sensor in the brain.

And others basically identified that the ventral surface of the brainstem, that is the part of the brainstem that's on this side,

was critical for that.

And then we identified a structure near the trapezoid nucleus.

It was not named in any of these neuroanatomical atlases.

So we just picked the name out of the hat, and we called it the retrotrapezoid nucleus.

If you go back in an evolutionary sense, and a lot of things that are hard to figure out begin to make sense when you look at the evolution of the nervous system, when control of facial muscles, going back to more primitive creatures because they had to take things in their mouth for eating, so we call that the face sort of developed, the eyes were there, the mouth is there.

These...

nuclei that contained the motor neurons, a lot of the control systems for them developed in the immediate vicinity.

So if you think about the face, there's a lot of sub-nuclei around there that had various roles at various different times in evolution.

And at one point in evolution, the facial muscles were probably very important in moving

fluid in and out of the mouth and moving air in and out of the mouth.