Synaptic function in the optic tectum

The synapse plays a key role in how neurons relay and compute information. The strength of synaptic connections, however, is not fixed; the nerve terminal acts as a computational unit in which the relation between input and output varies dynamically according to the activity of the network. These changes in synaptic strength occur over various time-scales and determine the behaviour of the whole organism by shaping the way information is processed in different regions of the nervous system. A major factor in modulating the release of neurotransmitter from a synapse is the activation of presynaptic receptors. This study focuses on presynaptic mechanisms that modulate synaptic strength in the retinotectal pathway in live zebrafish. These will be investigated using genetically modified zebrafish expressing fluorescent proteins that report vesicle fusion, pre- or postsynaptic calcium signals or membrane voltage. The expression of these proteins is driven by promoters which are specific for sensory neurons, including retinal ganglion cells and tectal neurons. By multiphoton confocal imaging of live transgenic zebrafish, I will be able to monitor the synaptic and electric activity of many labelled neurons simultaneously in real-time while applying optical stimuli. In combination with pharmacological and genetic manipulations, this approach enables me to assess changes in synaptic strength and the contributing pre- and postsynaptic mechanisms in a near phyiological setting. Thus, this research aims to understand how circuits of neurons transmit and transform signals in order to extract information about the world around us. Furthermore, my work will help to identify the contribution of specific (pre)synaptic receptors to the combined function of neural networks.