c. Imaging and Tract Tracing Core - Co-Directors: Tim Ebner, Glenn Giesler and Paul Mermelstein Overview and Significance: Purpose of the Core: The Imaging and Tract Tracing Core is designed to allow researchers from diverse experimental backgrounds to take advantage of modern imaging techniques. The Imaging and Tract Tracing Core is intended to strengthen the research of the investigators by providing access to experimental approaches, equipment and skilled personnel that would not normally be readily available. The Core provides researchers with a diverse array of imaging techniques, allowing investigators to probe, at both cellular and systems levels, normal functioning as well as genetically altered changes in brain function. Importance of Core Services: There are three major Divisions in the Imaging and Tract Tracing Core: Confocal Imaging, Tract Tracing/Histology and Activity-Dependent Optical Imaging. The Confocal Imaging Division allows studies ranging from the imaging of structures in single layers of cells to the examination of deeper tissue, in fixed slices and in vivo. The Division provides investigators access and training in single and multiphoton microscopy. The Tract Tracing/Histology Division allows investigators to examine genetic changes in the nervous system at both the cellular and systems level using anterograde and retrograde tracing methods. The Activity-Dependent Optical Imaging Division provides the equipment and technical expertise for in vivo imaging of neuronal activity in mice. Optical imaging of activity-dependent signals includes flavoprotein autofluorescence, voltage sensitive and calcium dyes, pH imaging, and the hemodynamic intrinsic signal. Necessity of the Core: The visualization of nervous system structure and function is one of the most powerful approaches to understanding questions being raised in neuroscience today. Individual laboratories at the University of Minnesota have expertise in specific imaging techniques, but no laboratory has the capability to apply all of these methods in a cohesive manner. In addition, while there are several confocal microscopes on campus, access is limited due to heavy use and for the vast majority of investigators, training is unavailable. The readily available expertise and equipment of the Core allows NINDS investigators to test questions in an integrative fashion, providing greater depth to their findings and driving their research forward.