Fast and light efficient remote focusing for volumetric voltage imaging

Voltage imaging holds great potential for biomedical research by enabling noninvasive recording of the electrical activity of excitable cells such as neurons or cardiomyocytes. Camera-based detection can record from hundreds of cells in parallel, but imaging entire volumes is limited by the need to focus through the sample at high speeds. Remote focusing techniques can remedy this drawback, but have so far been either too slow or light inefficient. Here, we introduce FLIPR, a new approach for remote focusing that doubles the light efficiency and enables high-speed volumetric voltage imaging at 500 volumes/s. We show the potential of our approach by combining it with lightsheet imaging in the zebrafish spinal cord to record from >100 spontaneously active neurons in parallel.