- NeuronBank AccessionID: Tri0002406
- Names and Aliases- Ventral Swim Interneuron A, VSI-A, or just swim interneuron.
- Species: Tritonia diomedea
- Neurotransmitter: Unknown
There is one VSI-A in each Cerebral ganglion. It is located near the DSIs. VSI is recognizable by its very small, broad spikes and high level of spontaneous activity.
VSI-A projects its axon contralaterally to the pedal ganglion.
It was initially reported that VSI-A was a component of the Tritonia swim Central Pattern Generator because it fires antiphasically to the DSIs and makes and receives synapses with DSI and C2. However, no effect of VSI-A on the motor pattern has ever been reported.
A second neuron, called VSI-B, on the ventral side of the pleural ganglion seems to be responsible for the ventral phase of the behavior.
- P. A. Getting, P. R. Lennard, and R. I. Hume. Central pattern generator mediating swimming in Tritonia. I. Identification and synaptic interactions. J.Neurophysiol. 44:151-164, 1980.
- P. A. Getting. Mechanisms of pattern generation underlying swimming in Tritonia. I. Neuronal network formed by monosynaptic connections. J.Neurophysiol. 46:65-79, 1981.
- P. S. Katz. Tritonia swim network. Scholarpedia 4 (5):3638, 2009. 
See also VSI