Motion Detectors in the Fruit Fly Eye

What am I looking at?

This video shows a 3D reconstruction of the structure and positions of hundreds of neurons in the fruit fly eye and optic lobe.  The gray and white outline containing the neurons shows the contours of the brain and optic lobe regions within. As the video progresses, we see three different types of neurons revealed: L1 neurons (green), Mi1 neurons (orange), and T4a neurons (blue). These neurons synapse with each other to form a basic communication pathway, also called a neural circuit, that is involved in detecting motion in the visual field. The synapses between the neurons are highlighted in red and yellow towards the end of the video.  

Biology in the Background

Fruit fly eyes have a different structure than ours do, but they serve similar functions: to detect light from the environment and send that information to the brain. The part of the fly’s brain that processes visual information is called the optic lobe. It contains many different types of neurons with distinct functions. These neurons communicate with each other to process various types of visual information, such as directional motion (to track moving objects), optic flow (helping flies navigate and estimate distances), and object detection (recognition of objects by their form and shape, and estimation of their size and distance).  

This video focuses on three different types of neurons that communicate with each other and help the fruit fly detect motion in the environment around them. Since fruit flies are such small insects, they are the target of a wide range of predators, so the ability to detect the motion of a possible predator is crucial to their survival.

The width of the optic lobe is around 0.2 millimeters, roughly 3 times the width of a human hair.

Technique

This video was created by reconstructing information gathered via Focused Ion Beam Scanning Electron Microscopy (FIB-SEM).