Aspects of Sensory Integration in the Crayfish Swimmeret System

The chief sensory effects observed in response to movement and position of a single swimmeret are ipsilateral reflexes such that the amplitude of spontaneous rhythmic activity is augmented when the swimmeret is held protracted, and diminished when the swimmeret is held retracted. A major source of these reflexes appears to be the non-spiking stretch receptors (NSSRs) at the base of the swimmeret. Sinusoidally-varying current injected into a single NSSR produces a beat-frequency modulation of spontaneously-generated rhythm very similar to that produced by applying sinusoidal movement to the whole swimmeret. The spontaneous rhythm does not entrain to the applied movement. Spiking receptors responding to movement and cuticle distortion may be largely responsible for a dynamic component of the reflex, and also for inconsistently-observed arousal effects and changes in frequency of spontaneously-generated rhythms.