Turn neurons

See it in a lesson

• Lesson 2

  How a fly knows which way it’s facing

  Push a real fly’s compass around and see what holds it in place.

  Where the lesson uses it

  1. Tap Stimulate to fire the left turn neurons (the turning signal). Then watch the compass dial.

     The compass neurons (the heading cells) light up on one side. That bright patch, the bump, marks which way the fly faces.

  2. Now tap Stimulate on the right turn neurons (the other signal). Keep your eyes on the bump.

     The bump swung around the dial. Turning signals from each side push it opposite ways, so the fly’s sense of direction turns too.

  Open the lesson→

Related terms

Compass neurons

A ring of nerve cells that keeps track of which way the fly is facing. Scientists call them E-PG neurons.

Activity bump

The patch of active compass neurons. Where it sits on the ring shows which way the fly is facing.

Ring neurons

Nerve cells that bring what the fly sees, such as landmarks, to the compass. They quiet the compass neurons, and that holds the bump in place.

Landmark

Something the fly sees that stays in place, like the sun or a tree. The fly uses it to keep its sense of direction steady.

Protocerebral bridge

A bar-shaped part of the fly’s brain, the protocerebral bridge. The compass neurons and the turn neurons both run through it.