In this work, the authors used fast optical motion tracking and 2p imaging to measure the activity of individual neurons in freely moving animals. No surgery. No optical window. No restraint. And all the benefits of multiphoton imaging.
The project was undertaken by Marc Gershow and his lab, principally co-first authors Doycho Karagyozov and Mirna Mihovilovic Skanata.
They built a two-photon, 3D tracking microscope. Using a technique employed in single molecule tracking studies, they scanned with a rotating laser beam and a resonant axial scanner, and then tracked motion using an FPGA-based feedback setup. The latency was 360 microseconds.
They used the system to record from neurons in freely moving Drosophila larvae, including visually responsive interneurons. Is this the first two photon recording of activity made in a brain that was not rigidly attached to the microscope objective? If you know of another, let us know.
This brief blog post doesn’t do the preprint justice. This is an unusually thorough write up of the work. The authors dug deep into the problem, and share a lot of analysis and technical details. Check it out.