3D random-access point scanning
3D random-access point scanning is the fastest method available with two-photon microscopes to read-out neuronal activity. It enables multiple points, distributed in 3D, to be imaged simultaneously. Within a large scanning volume, it can reach the 30 kHz scanning speed which is approximately one million times faster than other frame-by-frame scanning methods. This imaging speed means that thousands of individual neurons (e.g. in different cortical layers) can be measured with microsecond resolution simultaneously, revealing – for example – the dynamics of neuronal networks.
3D trajectory scanning
3D trajectory scanning has been improved from 3D random-access point scanning. The points are extended by drifting the focal point along short 3D trajectories which allows imaging without interruption at multiple dendritic branches. The sampling is continuous during the drift, so this scanning mode gives a more detailed spatial resolution without changing the overall scanning time: this remains as high as during the point scanning. As a result, the function of thin dendritic segments, or even spines and single action potentials can be revealed.