Methods, Trade-offs, and Opportunities in High-speed Optical Microscopy for Neural Voltage imaging

Electrical signals in neurons underlie perception, movement, memory, and behaviour, yet many unfold too rapidly to be captured by conventional optical imaging. Calcium imaging has transformed neuroscience but provides an indirect and relatively slow readout of electrical activity. By directly measuring membrane-potential changes, voltage imaging enables millisecond-scale recording of action potentials, subthreshold dynamics, and signal propagation across neural circuits. Recent advances in voltage-sensitive dyes and genetically encoded voltage indicators have made voltage imaging increasingly practical, motivating the development of fluorescence microscopy methods optimized for high-speed acquisition. However, voltage imaging remains constrained by trade-offs among imaging speed, spatial resolution, signal-to-noise ratio, and photodamage. In this Review, we discuss high-speed optical microscopy strategies that address these challenges and highlight the need for co-design among voltage indicators, imaging systems, and computational analysis.