The ability to image neurons anywhere in the mammalian brain is a major goal of optical microscopy. Here we describe a minimally invasive microendoscopy system for studying the morphology and function of neurons at depth. Utilizing a guide cannula with an ultrathin wall, we demonstrated in vivo two-photon fluorescence imaging of deeply buried nuclei such as the striatum (2.5 mm depth), substantia nigra (4.4 mm depth) and lateral hypothalamus (5.0 mm depth) in mouse brain. We reported, for the first time, the observation of neuronal activity with subcellular resolution in the lateral hypothalamus and substantia nigra of head-fixed awake mice.
Keywords: (110.2760) Gradient-index lenses; (170.2150) Endoscopic imaging; (170.2655) Functional monitoring and imaging; (180.0180) Microscopy; (180.2520) Fluorescence microscopy; (180.4315) Nonlinear microscopy.