RT Journal Article SR Electronic T1 A large field of view two-photon mesoscope with subcellular resolution for in vivo imaging JF bioRxiv FD Cold Spring Harbor Laboratory SP 055947 DO 10.1101/055947 A1 N. J. Sofroniew A1 D. Flickinger A1 J. King A1 K. Svoboda YR 2016 UL http://biorxiv.org/content/early/2016/06/01/055947.abstract AB Imaging is used to map activity across populations of neurons. Microscopes with cellular resolution have small (< 1 millimeter) fields of view and cannot simultaneously image activity distributed across multiple brain areas. Typical large field of view microscopes do not resolve single cells, especially in the axial dimension. We developed a 2-photon random access mesoscope (2p-RAM) that allows high-resolution imaging anywhere within a volume spanning multiple brain areas (Ø 5 mm × 1 mm cylinder). 2p-RAM resolution is near diffraction limited (lateral, 0.66 μm, axial 4.09 μm at the center; excitation wavelength = 970 nm; numerical aperture = 0.6) over a large range of excitation wavelengths. A fast threedimensional scanning system allows efficient sampling of neural activity in arbitrary regions of interest across the entire imaging volume. We illustrate the use of the 2p-RAM by imaging neural activity in multiple, non-contiguous brain areas in transgenic mice expressing protein calcium sensors.