How a fly remembers a smell

About this lesson

Send a smell into a real fruit fly brain, follow it to the mushroom body, and find where its memory is stored. A free 10-minute lesson.

What happens, step by step

1. 1

   A fly smells with its antennae (its two feelers). Tap Stimulate to send a smell in. Watch the orange neurons light up.

   Those orange smell receptors (the smell catchers) fire first. Every smell starts here.

2. 2

   Tap Stimulate again and follow the colors. Yellow projection neurons (the smell messengers) carry the smell inward. Blue Kenyon cells (the smell sorters) catch it next.

   The blue cells turn each smell into its own pattern.

3. 3

   Tap Stimulate once more. Now watch the pink output neurons (the memory readers). They read the blue pattern.

   When a smell comes with sugar or danger, the links from blue to pink change. Scientists think that change is the memory.

4. 4

   Now silence the Kenyon cells (the smell sorters). We will send the smell for you. What disappears?

   The pink light almost vanishes. The smell still gets in, but the memory readers get nothing to read.

5. 5

   Tap the Kenyon cells (the smell sorters) button again to switch them back on. We will send the same smell.

   The pink light comes back. The fly can read its smell memory again.

Questions this lesson answers

How do flies smell?

A fly smells mainly with its two antennae. Smell receptors on them fire when an odor lands, and the signal travels into the brain to be sorted.

Do flies have memories?

Yes. A fruit fly can learn that a smell means food or danger and remember it for hours or days. The memory forms in the mushroom body.

Key terms

• Antennae
• Smell receptors
• Antennal lobe
• Projection neurons
• Mushroom body
• Kenyon cells
• Output neurons

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