The study of the nervous system requires to an exceptional extent observation of and experimentation on intact tissue. There, in particular, high-resolution optical microscopy benefits from the inherent advantages of multi-photon fluorescence excitation. Several cases will be presented from a number of different tissues and organisms, where multi-photon excited laser scanning fluorescence microscopy has been an essential experimental tool. Those examples include the discovery of biochemical coincidence detection in synaptic spines and the clarification of the underlying mechanism; the observation of sensory evoked dendritic signaling in intact animals and the observation of light induced calcium signals in the intact retina. Recently a fiber coupled two-photon microscopy has been developed that allows the imaging in moving animal.
"Multiphoton microscopy in neuroscience", Proc. SPIE 4620, Multiphoton Microscopy in the Biomedical Sciences II, (17 June 2002); doi: 10.1117/12.470676; https://doi.org/10.1117/12.470676