UC Berkeley

Understanding the neural mechanisms that guide behavior is one of the biggest quests in neuroscience. This question is tackled at different levels of analysis, from studying whole-brain blood oxygenation levels in humans, to minuscule receptor movements in cells. In this dissertation, I describe work aiming to explore the neural basis of behavioral improvement in the larval zebrafish from the network level, across brain areas, to the neuron level, looking at specific neuronal ensembles.In chapter one, I introduce the study of experience dependent changes in behavior through history and describe the advantages of using the ethologically relevant prey capture behavior in larval zebrafish as a model. In chapter two, in collaboration with Claire Oldfield, I studied how experience hunting live prey affects prey capture behavior and the underlying neural activity. I show that previous experience with live prey improves hunting performance compared to larvae that have been fed with inert fish flakes. Consequently, looking at whole-plane neural activity, I observed no differences in the neural representations of prey in the visual areas, however, experienced fish showed increased correlations between output neurons of the tectum and the forebrain, and an increased probability for visual activity to evoke motor action. This led to the hypothesis that experience may lower the threshold for visual information transfer to motor areas, via an increase of activity in the forebrain. To test this hypothesis, I specifically ablated cells in the habenula, one of the forebrain structures, and observed a reduction in eye convergences and prey consumption. These findings show the involvement of the forebrain in experience-dependent improvement of prey capture for the first time. In chapter three, I describe our attempts to study experience-dependent changes in forebrain activity and network dynamics between visual areas and the forebrain at a single-cell resolution, using multi-plane two-photon imaging. This project is still at its beginnings, but I describe the adaptation of the behavioral paradigm to the two-photon microscope, and the potential of recording large populations of neurons at cellular level during a naturalistic behavior.