Cerebellar-Dependent Learning in Larval Zebrafish

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. The developing zebrafish (Danio rerio) is an animal model that circumvents these problems, because zebrafish larvae possess a rich behavioral repertoire and an accessible brain. Here, we developed a classical conditioning paradigm in which 6- to 8-d-old larvae develop an enhanced motor response to a visual stimulus (conditioned stimulus, CS) when it is paired with touch (unconditioned stimulus, US). Using in vivo calcium imaging we demonstrate that CS and US activate different subsets of neurons in the cerebellum; their activity, modulated by learning two-photon laser ablation, revealed that the cerebellum is involved in acquisition and extinction, but not the retention, of this memory

Dynamics of evaporative colloidal patterning

Drying suspensions often leave behind complex patterns of particulates, as might be seen in the coffee stains on a table. Here we consider the dynamics of periodic band or uniform solid film formation on a vertical plate suspended partially in a drying colloidal solution. Direct observations allow us to visualize the dynamics of the band and film deposition, and the transition in between when the colloidal concentration is varied. A minimal theory of the liquid meniscus motion along the plate reveals the dynamics of the banding and its transition to the filming as a function of the ratio of deposition and evaporation rates. We also provide a complementary multiphase model of colloids dissolved in the liquid, which couples the inhomogeneous evaporation at the evolving meniscus to the fluid and particulate flows and the transition from a dilute suspension to a porous plug. This allows us to determine the concentration dependence of the bandwidth and the deposition rate. Together, our findings allow for the control of drying-induced patterning as a function of the colloidal concentration and evaporation rate.Comment: 11 pages, 7 figures, 2 table