Networking at the VNC

What am I looking at?

This video shows neurons within the VNC of a fruit fly as they’re progressively stacked on top of each other. Each image represents a different dataset, and they were all digitally fitted together. By the end of the video, you can see a rough neuronal map within the VNC. The VNC is responsible for processing movement signals sent from the brain to the muscles; generating movement patterns (for walking or flying, for example); and then processing feedback from the fly’s various mechanosensory organs.

Biology in the background

The VNC in an insect performs functions similar to those of the spinal cord in a vertebrate, like a human. In a fruit fly, the VNC contains about 23,000 neurons, and its brain contains about 135,000 neurons, whereas a human brain contains over 100 billion neurons.

The neurons in any organism’s nervous system communicate with each other, as well as with other cells in the body, by sending electrical or chemical signals via connection points called synapses. Researchers have long been trying to construct maps of these connections to give them a better understanding of the mechanisms behind this communication. These maps are called connectomes.

Through such work, we know that the VNC in a fruit fly is relatively autonomous, capable of functioning independently of the brain in some cases. It can coordinate the fly’s movements, maintain its pattern of breathing, and regulate its reflexive responses to stimuli without the involvement of the brain. Sensory information, such as from the fly’s environment or from forces acting on its exoskeleton, is also processed in the VNC – and some of it never reaches the brain.

The VNC in a fruit fly is about 500 micrometers long, or roughly seven times larger than the width of a human hair.

The original publication of this work can be viewed here: A searchable image resource of Drosophila GAL4 driver expression patterns with single neuron resolution.

Technique

This image was created using confocal microscopy.