Compact semiconductor light-emitting diodes for dynamic imaging of neuronal circuitry

We describe the use of compact green light-emitting diodes (LEDs) for fluorescence optical imaging and demonstrate this for dynamic recording from cultured neurons. The efficient gallium-nitride-based LEDs have individual element sizes comparable to typical biological cells and are operated in proximity illumination mode for individual neurons. As periodic arrays, and with direct electrical control of each LED, a spatially periodic multicellular target can be induced to fluoresce in a predesigned spatiotemporal sequence, thereby providing a new approach to dynamic recording of small neural circuits.