| Optical imaging of membrane potential is one of the most promising methods for experimentally addressing the question of how activity is coordinated in groups of cells in the brain. However, a suitable optical voltage reporter providing single-cell resolution for general in vivo use has not been developed. Here we describe the rational optimization of the genetically encodable fluorescent voltage reporter hVOS. A simplified quantitative model of hVOS was used to guide optimization, yielding an approximate three-fold improvement in fractional fluorescence change, as recorded by wide-field fluorescence microscopy and two photon laser scanning microscopy. The optimized voltage reporter was then used for optical recordings in the Drosophila antennal lobe, where evoked activity was recorded with millisecond resolution. |
