Meeting Abstract
The ability of a moving animal to discriminate external stimuli from self-generated stimuli is important to maintain sensitivity to biologically relevant cues. The lateral line system allows fishes to detect hydrodynamic cues in their fluid environment. This is possible because the deflection of mechanosensory neuromasts by fluid motion results in an increased frequency of action potentials in the afferent neurons. Afferent neurons are also spontaneously active which has been shown to maintain sensitivity and frequency discrimination. During swimming self-generated fluid motion stimulates the lateral line, and efferent neurons in the hindbrain send a corollary discharge of the motor command to modulate action potential activity by controlling hair cell transmitter release. By simultaneously recording from afferent neurons and ventral motor roots using extracellular recordings in 4-6 day post fertilization larval zebrafish (Danio rerio), we discovered that the spontaneous frequency of afferent action potentials decreased during fictive swimming. For more than 280 swim events across 34 individuals, we found that afferent spontaneous activity was completely inhibited during 62% of swim events. Higher spontaneous spike rates were correlated to a lower likelihood of afferent inhibition. To quantify the functional contribution of cholinergic efferent neurons, we selectively labeled and then ablated their hindbrain soma with ultraviolet light. Electrophysiological recordings revealed that the likelihood of afferent inhibition was reduced by approximately 50% after ablation. This study indicates that the lateral line system is less sensitive during locomotion and suggests that the cholinergic efferent system works to limit sensory feedback.
