Two‐photon imaging of fiber‐coupled neurons

Optical coupling between a single, individually addressable neuron and a properly designed optical fiber is demonstrated. Two‐photon imaging is shown to enable a quantitative in situ analysis of such fiber–single‐neuron coupling in the live brain of transgenic mice. Fiber‐optic interrogation of single pyramidal neurons in mouse brain cortex is performed with the positioning of the fiber probe relative to the neuron accurately mapped by means of two‐photon imaging. These results pave the way for fiber‐optic interfaces to single neurons for a stimulation and interrogation of individually addressable brain cells in chronic in vivo studies on freely behaving transgenic animal models, as well as the integration of fiber‐optic single‐neuron stimulation into the optical imaging framework. Fiber‐optic components offer a versatile platform for the development of innovative neurointerfaces, as well as flexible microprobes for deep‐brain optical interrogation. The development of methods whereby optical fibers could be reproducibly coupled to individual neurons stands alone as a fundamental challenge. Here, we apply two‐photon imaging as a tool to validate optical coupling between a fiber‐optic probe and individual neurons in a live brain of transgenic mice.