DESCRIPTION (provided by applicant): Over the next 5 years, the main objective of this project will be to analyze visually evoked synaptic activity in tectal neurons of Xenopus tadpoles. In particular, the temporal and spatial patterns of active regions on the dendritic trees will be examined during development in general and also during periods of induced changes in synaptic strength. To this end patterned visual stimulation and multiple patch-clamp recordings of tectal cells will be combined with simultaneous multi-photon laser scanning calcium imaging. Patch clamp recordings will provide the amplitude and the fast temporal dynamics of synaptic responses and two-photon calcium imaging will reveal the spatial pattern in three dimensions. Synapses will be activated by direct electrical stimulation of retinal ganglion cells as well as by visual images presented to the retina. To induce changes in synaptic connectivity several electrical and visual stimulation paradigms will be used. These experiments will provide new information about dendritic integration of complex physiological inputs and about the development of receptive fields in the vertebrate visual system.