Dr. Charles Zuker

Coffee, it has an associated gain to the system.

And that gain to the system, that positive valence that emerges out of that negative signal is sufficient to create that positive association.

And in the case of coffee, of course, it's caffeine activating a whole group of neurotransmitter systems that give you that high associated with coffee.

So yes, this taste system is changeable, it's malleable, and it's subjected to learning and experience.

Where does this desensitizing happens?

That's the term that we use.

I think it's happening at multiple stations.

It's happening at the receptor level, i.e.

the cells in your tongue that are sensing that sugar.

As you activate this receptor and it's triggering activity after activity after activity, eventually you exhaust the receptor.

Again, I'm using terms which are extraordinarily loose.

The receptor gets to a point where it undergoes a set of changes, chemical changes, where it now signals far less efficiently.

or even gets removed from the surface of the cell.

And that is a huge side of this modulation.

And then the next, I believe, is the integrated, again, loss of signaling that happens by continuous activation of the circuit at each of these different neural stations.

from the tongue to the ganglia, from the ganglia to the first station in the brainstem, a second station in the brainstem to the thalamus, then to the cortex.

So there are multiple steps that this signal is traveling.

Now you might say, why, if this is a label line, why do you need to have so many stations?

And that's because the taste system is so important to ensure

that you get what you need to survive, that it has to be subjected to modulation by the internal state.