Neurons of the VNC
These colorful blobs and strings represent a very detailed connectome of the Ventral Nerve Cord (VNC) of a male adult fruit fly. OK, yes, that’s a lot to take in, but let’s hit the high points: a connectome is a map of the connections between neurons in the nervous system, and the ventral nerve cord is the area in the fruit fly nervous system that controls most of its movement (the insect analog of our spinal cord).
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DownloadNeurons of the VNC
These colorful blobs and strings represent a very detailed connectome of the Ventral Nerve Cord (VNC) of a male adult fruit fly. OK, yes, that’s a lot to take in, but let’s hit the high points: a connectome is a map of the connections between neurons in the nervous system, and the ventral nerve cord is the area in the fruit fly nervous system that controls most of its movement (the insect analog of our spinal cord).
What am I looking at?
Researchers at HHMI’s Janelia Research Campus mapped all ~23,000 neurons in the VNC to create this connectome. The video begins by showing a small sample (about 4%) of the neurons mapped within the VNC to provide an idea of the broad categories of neurons mapped and visual examples of how they are connected. Individual neurons are shown in different colors to more easily distinguish them from each other. The video moves on to show the neruomeres (different compartments) of the VNC. Then various classes of neurons: ascending sensory neurons, sensory neurons that terminate in the VNC, descending neurons, ascending neurons, intrinsic neurons, motor neurons, and finally a combined view showing examples of all classes together.
Biology in the Background
The ventral nerve cord is the area of the fruit fly’s nervous system that controls most of its movement, also called its motor functions. There are a variety of different broad classes of neurons that work together to allow the VNC to do this. This video shows samples from six of them.
The first group of neurons shown are ascending sensory neurons. Sensory neurons are neurons that provide sensory information (things like touch, vision, and smell) to the VNC or the brain. Ascending sensory neurons are neurons that gather sensory information from the body (also called the periphery) and pass it directly to the brain, running through the VNC but not providing it with significant input. Next, we see sensory neurons that terminate in the VNC, meaning the information gathered by these neurons is provided directly to the VNC and is processed locally before traveling to the brain, if at all.
Then we see descending neurons, which are neurons that send information from the brain to the VNC. After that, we see ascending neurons, which differ from the ascending sensory neurons described earlier because instead of sending information from the periphery to the brain, they send information from the VNC to the brain. Next, we see intrinsic neurons, which are neurons that are completely contained within the VNC and aid in information processing there. Finally, we see motor neurons. These are the neurons that send signals to the muscles in the body to control their movement.
All these neurons together allow the fly to sense the environment around it, process information, and move its body to respond to sensory cues. This includes extremely quick reflex responses that help the fly escape from danger.
Neuron digital reconstructions like the ones in this video can provide researchers with a more complete understanding of how different groups of neurons in the nervous system control functions like movement. This knowledge could be the foundation for additional research on how this process works in other organisms, even humans.
Technique
This video was created by mapping images gathered via Focused Ion Beam Scanning Electron Microscopy (FIB-SEM), with a combination of automated and manual image analysis.
Elizabeth Marin, Philip Hubbard, the HHMI Janelia FlyEM Project Team, Google, the University of Cambridge