Extended field-of-view ultrathin microendoscopes for high-resolution two-photon imaging with minimal invasiveness
Andrea Antonini, Andrea Sattin, Monica Moroni, Serena Bovetti, Claudio Moretti, Francesca Succol, Angelo Forli, Dania Vecchia, Vijayakumar P. Rajamanickam, Andrea Bertoncini, Stefano Panzeri, Carlo Liberale, Tommaso Fellin
Abstract
Imaging neuronal activity with high and homogeneous spatial resolution across the field-of-view (FOV) and limited invasiveness in deep brain regions is fundamental for the progress of neuroscience, yet is a major technical challenge. We achieved this goal by correcting optical aberrations in gradient index lens-based ultrathin (≤500 µm) microendoscopes using aspheric microlenses generated through 3D-microprinting. Corrected microendoscopes had extended FOV ( eFOV ) with homogeneous spatial resolution for two-photon fluorescence imaging and required no modification of the optical set-up. Synthetic calcium imaging data showed that, compared to uncorrected endoscopes, eFOV -microendoscopes led to improved signal-to-noise ratio and more precise evaluation of correlated neuronal activity. We experimentally validated these predictions in awake head-fixed mice. Moreover, using eFOV- microendoscopes we demonstrated cell-specific encoding of behavioral state-dependent information in distributed functional subnetworks in a primary somatosensory thalamic nucleus. eFOV- microendoscopes are, therefore, small-cross-section ready-to-use tools for deep two-photon functional imaging with unprecedentedly high and homogeneous spatial resolution.