Motor behaviour selectively inhibits hair cells activated by forward motion in the lateral line of Zebrafish

Abstract

How do sensory systems disambiguate events in the external world from signals generated by the motor behaviour of the animal? One strategy is to suppress the sensory input whenever the motor system is active, but the cellular mechanisms remain unclear. We investigated how motor behaviour modulates signals transmitted by the lateral line of zebrafish, which senses pressure changes around the body of the animal. Activation of motor neurons during fictive swimming caused co-activation of efferent fibers and suppression of synaptic transmission from the primary mechanoreceptors, the hair cells. In some hair cells, a single motor spike inhibited glutamate release by about 50% and block was often complete within 50-100 ms of the start of swimming. All hair cells polarized to be activated by posterior deflections, as would occur during forward swimming, were suppressed by >90%, while only half of those polarized in the anterior direction were inhibited and by an average of just 45%. The selective inhibition of hair cells activated during motor behaviour provides a mechanism for the suppression of self-generated signals while maintaining sensitivity to stimuli originating in the external world.