Different command neurons select different outputs from a shared premotor interneuron of crayfish tail-flip circuitry

In the crayfish a bilateral pair of interneurons (the 13's) are involved in the generation of two types of tail-flip escape responses, one mediated by giant neurons and the other by nongiant circuitry. The 13's make a variety of output connections with the motoneurons and with other interneurons involved in tail flipping. The motoneuronal outputs include strong synapses on telson flexor motoneurons, whose activity during tail flips mediated by lateral giant fibers would be maladaptive. The lateral giants always drive the 13's, but also drive inhibitory neurons that prevent the undesirable outputs of the 13's while permitting their adaptive outputs to be expressed. It is often adaptive for tail flips initiated by nongiant circuitry to utilize the telson flexor muscles that 13 strongly excites. During such tail flips 13 is often fired, and this firing is important in driving the telson flexors.