Welcome to Quantum Magazine's podcast.

Each episode, we bring you stories about developments in science and mathematics.

I'm Susan Vallett.

Our brain encodes memories as either positive or negative.

And it turns out that a single molecule determines

which way they'll go. That's next. Quantum Magazine is an editorially independent online

publication supported by the Simon's Foundation to enhance public understanding of science.

Imagine you're on a vacation of a lifetime in Kenya, traversing the Savannah on safari.

The tour guide points out elephants to your right and lions to your left.

It's amazing.

Years later, you walk into a florist's shop in your hometown and smell something like the flowers

on the jackalberry trees that dotted the landscape.

When you close your eyes, the store disappears and you're back in the land rover.

Inhaling deeply, you smile at the happy memory.

Now, let's rewind a minute.

Imagine you're on the vacation of a lifetime in Kenya, traversing the savanna on safari.

The tour guide points out elephants to your right and lions to your left.

From the corner of your eye, you notice a rhino trailing the vehicle.

Suddenly it sprints toward you, and the tour guide yells at the driver to hit the gas.

You panic. Your adrenaline spikes. You think you're going to die.

Years later, when you walk into that florist shop,

the sweet floral scent makes you shudder. How Lee is a postdoctoral researcher at the Salk Institute

...