Structural Properties of the Caenorhabditis elegans Neuronal Network
The C. elegans nervous system contains 302 neurons and is divided into the pharyngeal nervous system containing 20 neurons and the somatic nervous system containing 282 neurons.
We updated the wiring diagram (see Methods) of the larger somatic nervous system. Since neurons CANL/R and VC06 do not make synapses with other neurons, we restrict our attention to the remaining 279 somatic neurons.
The wiring diagram consists of 6393 chemical synapses, 890 gap junctions, and 1410 neuromuscular junctions.
Although the updated wiring diagram represents a significant advance, it is only about 90% complete because of missing data and technical difficulties.
Neurons are divided into 118 classes, based on morphology, dendritic specialization, and connectivity. Based on neuronal structural and functional properties, the classes can be divided into three categories: sensory neurons, interneurons, and motor neurons.
Neurons known to respond to specific environmental conditions, either anatomically, by sensory ending location, or functionally, are classified as sensory neurons. They constitute about a third of neuron classes. Motor neurons are recognized by the presence of neuromuscular junctions.
Interneurons are the remainder of the neuron classes and constitute about half of all classes. A few of the neurons could have dual classification, such as sensory/motor neurons. Some interneurons are much more important for developmental function than for function in the final neuronal network.
Wiring diagram as adjacency matrices
Adjacency matrices for the gap junction network (blue circles) and the chemical synapse network (red points) with neurons grouped by category (sensory neurons, interneurons, motor neurons).
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