The rapid advance of genetically encoded functional indicators allows the scientists to visualize neuronal activities with light in the living brain at high spatiotemporal resolutions. For in vivo measurement in the mammalian brain, laser scanning two-photon fluorescence microscopy (TPM) is commonly employed to image the neurons expressing genetically encoded functional indicators. The sequential point scanning of TPM offers clean measurement without noise crosstalk and yields excellent signal-to-noise ratio. However, the commonly employed systems are designed to accommodate single-plane recording at ~10 Hz rate. The emerging high-speed glutamate sensors and voltage indicators often require much greater frame rate (e.g. 400-1000 Hz). Moreover, for 3D multiregional recording of calcium indicators (e.g. 20 sub image planes at 40 Hz), image frame rate near 1000 Hz is also required. Here we propose to develop an optical gearbox, which as an add-on unit can convert commonly used laser scanning two-photon microscopes for high frame rate recording. The essence of optical gearbox is to conserve the maximum overall data throughput of an imaging system and allow the users to gain scanning line rates at the cost of imaging field-of-view (FOV). For laser scanning microscopes based on galvo, resonant galvo or polygon scanners, the system achieves the highest data throughput only at full FOV scanning. Zoom (reducing FOV) leads to proportionally reduced data throughput. In comparison, with optical gearbox, there will be no loss on data throughput. Based on the optical gearbox, we will develop the capability for two applications. One is the high frame rate 2D imaging suitable for glutamate and voltage sensors and the other is to distribute the kHz frame rate for multiple regions in 3D for multiregional calcium imaging (e.g. image tens of 3D regions at tens of Hz rate). The development of this add-on converter will enable high speed 3D imaging with the existing two- photon microscopes without the need to have specialized and expensive new laser sources, hardware and software. This development will broadly facilitate the research community to take advantages of the advance of high-speed functional indicators in neuroscience research.