Cerebellar-Dependent Learning in Larval Zebrafish
New conditioning paradigm in zebrafish larvae reveals associative learning mediated by cerebellar neurons
Understanding how neuronal network activity contributes to memory formation is challenged by the complexity of most brain circuits and the restricted ability to monitor the activity of neuronal populations in vivo. Recently, however, the developing zebrafish (Danio rerio) emerged as a model system that circumvents these problems because larval zebrafish possess a rich behavioral repertoire and an accessible brain with circuits that are homologous to mammalian systems. Despite these clear advantages, robust learning paradigms in the larval fish have not been described.
Mark Aizenberg and Erin Schuman at the MPI for Brain Research in Frankfurt have now developed a classical conditioning paradigm in which zebrafish larvae learned to associate a light stimulus (conditioned stimulus) with a tactile stimulus (unconditioned stimulus). These studies published in the Journal of Neuroscience demonstrate for the first time that larval zebrafish can exhibit associative learning. In vivo calcium imaging further revealed that successful learning is accompanied by changes in the response properties of cerebellar neurons. Ablation of the cerebellum abolished the conditioned response, but did not affect the unconditioned response, indicating that the cerebellum is an important structure that mediates the learned behavior.