Integration of Single-Photon Miniature Fluorescence Microscopy and Electrophysiological Recording Methods for in vivo Studying Hippocampal Neuronal Activity

The miniature single-photon fluorescent microscope (miniscope)enables the visualization of calcium activity in vivo in freelymoving laboratory animals, providing the capability to track cellularactivity during the investigation of memory formation, learning,sleep, and social interactions. However, the use of calcium sensorsfor in vivo imaging is limited by their relatively slow (millisecond-scale)kinetics, which complicates the recording of high-frequency spikeactivity. The integration of methods from single-photon miniaturefluorescent microscopy with electrophysiological recording, whichpossesses microsecond resolution, represents a potential solutionto this issue. Such a combination of techniques allows for the simultaneousrecording of optical and electrophysiological activity in a singleanimal in vivo. In this study, a flexible polyimide microelectrodewas developed and integrated with the gradient lens of the miniscope.The in vivo tests conducted in this research confirmed that themicroelectrode combined with the gradient lens facilitates simultaneoussingle-photon calcium imaging and local field potential recordingin the hippocampus of an adult mouse.