Book excerpt: These are exciting times for the field of optical imaging of brain function. Rapid developments in theory and technology continue to considerably advance understanding of brain function. Reflecting changes in the field during the past five years, the second edition of In Vivo Optical Imaging of Brain Function describes state-of-the-art techniques and their applications for the growing field of functional imaging in the live brain using optical imaging techniques. New in the Second Edition: Voltage-sensitive dyes imaging in awake behaving animals Imaging based on genetically encoded probes Imaging of mitochondrial auto-fluorescence as a tool for cortical mapping Using pH-sensitive dyes for functional mapping Modulated imaging Calcium imaging of neuronal activity using 2-photon microscopy Fourier approach to optical imaging Fully updated chapters from the first edition Leading Authorities Explore the Latest Techniques Updated to reflect continuous development in this emerging research area, this new edition, as with the original, reaches across disciplines to review a variety of non-invasive optical techniques used to study activity in the living brain. Leading authorities from such diverse areas as biophysics, neuroscience, and cognitive science present a host of perspectives that range from a single neuron to large assemblies of millions of neurons, captured at various temporal and spatial resolutions. Introducing techniques that were not available just a few years ago, the authors describe the theory, setup, analytical methods, and examples that highlight the advantages of each particular method.