Functional Organization of Visual Motion-Processing Neurons in the Zebrafish Pretectum

Abstract

The transformation of visual input into behavior requires the processing of complex information in brain-scale neural circuits. Therefore, mapping and modeling the connectivity and dynamics of these neural circuits is important for understanding their function. Using the optically transparent larval zebrafish as a model, I investigated the neural circuitry underlying the optomotor response (OMR), a visually guided stabilization behavior. Through two-photon calcium imaging, I characterized the functionally diverse motion-processing neurons that connect and influence dynamics in the pretectum, a conserved brain region involved in visual processing. To classify excitatory and inhibitory neurons responsive to visual motion stimulation, I hierarchically clustered these motion-processing neurons based on their stimulus response properties. I demonstrate that neural classes with similar functional properties share anatomical and molecular characteristics. Specifically, groups of neurons with stronger directional tuning and suppression to their non-preferred direction tend to be located in the posterior pretectum and are glutamatergic, suggesting a functional specialization of these complex response classes. To predict how connectivity among these classes gives rise to motion-processing circuit dynamics, I trained recurrent neural network (RNN) models constrained by known pretectal anatomy and activity from motion-processing neurons. Analysis of learned connectivity weights reveals that neurons with similar stimulus responses form connected groups and possess similar connectivity patterns. Thus, the model predicts that connectivity is related to a neuron’s stimulus response type. Finally, I report that diversity in motion processing neuron properties found across fish is reflected by how predictive these properties are of learned connectivity weights. These findings advance our understanding of how diverse neurons transform visual motion input into perception and behavior, while highlighting individual variations in visual processing.