Dr. Charles Zuker

And each of these nodes provides a new site to give it plasticity and modulation.

I'm going to give you one example of how the internal state changes the way the taste system works.

Salt

is very appetitive at low concentrations.

And that's because we need it.

It's our electrolyte balance requires salt.

Every one of their neurons uses salt as the most important of the ions, you know, with potassium to ensure that you can transfer these electrical signals within and between neurons.

But at high concentrations, let's say,

Ocean water is incredibly aversive.

And we all know this because we've gone to the ocean and then when you get it in your mouth, it's not that great.

However, if I salt deprive you, now this incredibly high concentration of salt, one molar sodium chloride, becomes amazingly appetitive and attractive.

What's going on in here?

Your tongue is telling you this is horrible, but your brain is telling you you need it.

And this is what we call the modulation of the taste system by the internal state.

Yes.

You know, the brain...

needs to monitor the state of every one of our organs.

It has to do it.

This is the only way that the brain can ensure that every one of those organs are working together in a way that we have healthy physiology.

This is a two-way highway where the brain is not only monitoring, but is now modulating back what the body needs to do.