Abstract

Behaviour is often driven by both the current environment and experiences from the recent past. How does the brain integrate these sources of information? Here, using whole-brain imaging during behaviour, we identify an inhibitory brain region in the larval zebrafish dorsal hindbrain (DH cells) that integrates stimuli over time. DH cells detect visual input that promotes swimming, integrate this in ongoing activity, and determine how quickly the animal responds to future stimuli (motor readiness). They do this in between actions, and reset after each movement. Optogenetic activation of the DH cells increases motor readiness, but suppresses current motor output, suggesting that the DH cells cause a rebound in the motor system. We show that DH cells project to the inferior olive, and confirm that these cells inhibit this nucleus and cause a rebound upon release. Using neuronal network models, we show that these results imply that inhibitory integrators are complementary to integrate-to-bound models for sensory integration and motor planning.