When mice are low on salt, a specific group of brain cells makes them desperately want to eat salt—even if it tastes bad—and these cells also make the mice feel bad, so they do things to stop the feeling.

Mice stop wanting salt almost instantly when they taste it in their mouth—even before the salt gets into their body—and this happens because a specific brain signal turns off when salt is tasted.

These brain cells only make mice want salt—not water or food—and don’t affect how much they move around.

When mice taste salt, a different group of brain cells that use a calming chemical (GABA) gets turned on and sends a 'stop' signal to the salt-craving cells, making them quiet down.

When the body is low on salt, special cells in the brainstem that detect this imbalance send a 'go' signal to the salt-craving neurons, turning them on.

The brain uses two different signals to control salt craving: one slow signal that says 'we need salt' and one fast signal that says 'you tasted salt, stop now'—and they work together to make the mouse eat just enough.