Jeffrey N. Stirman, Ikuko T. Smith, Michael W. Kudenov, Spencer L. Smith
Two-photon calcium imaging can provide an optical readout of spiking activity with cellular resolution, revealing activity correlations and population dynamics within an individual cortical area. However, many conventional two-photon imaging systems maintain cellular resolution only over a field of view (FOV) ~500 μm wide. This FOV precludes the simultaneous visualization of multiple cortical areas, which can be spread over a millimeter or more. Thus it has not typically been possible to use two-photon calcium imaging to measure neural activity dynamics and correlations between cortical areas. Here, we demonstrate a new two-photon imaging system that is designed to image neural activity in multiple cortical areas simultaneously. Low aberration scan optics support an expanded FOV with cellular resolution that is 1.4 to 1.8 mm wide using a commercially available objective, and 3.5 mm wide using a custom objective. Two independently positionable multiplexed excitation pathways simultaneously image any two regions within the expanded FOV. We use this new imaging system to measure activity correlations between two cortical visual areas in mice.