New 2-photon microscope exceeds speed imaging brain imaging

A new 2-photon microscope that “breaks a long-standing speed limit” for brain activity analysis was built by a group of scientists at the Janelia Research Campus of the Howard Hughes Medical Institute.

The microscope, which would be 15 times faster than previously thought possible by the scientists themselves, is so fast in collecting data that it can also record the voltage peaks of the same neurons and the release of chemical messengers over large areas of the brain. This allows for the simultaneous monitoring of hundreds of synapses, something that was previously considered a dream by neuroscientists involved in brain imaging and that today could be a reality of everyday life.

These are events that, in addition to having to be analyzed in the brains of patients or live animals (and this already poses great difficulties because a living brain is substantially impenetrable with the classic optical microscopy), can last only a few milliseconds. The study, published in Nature Methods, explains how the “classic” two-photon microscopes can encounter difficulties in analyzing brain activities since each measurement requires several nanoseconds. This limits the speed at which an image can be captured and therefore limits the data that can be acquired.

“We exceeded this limit by compressing the measurements,” says Kaspar Podgorski, one of the researchers working on the project. It refers to measurements of what might appear to be a fundamental limit, ie the number of pixels multiplied by the minimum time per pixel.

The new device is a scanning-line angular projection microscope (Scanned Line Angular Projection or SLAP), which allows a beam of light to pass over a sample through four different levels and does not record every pixel of the beam but compresses the points of the ray line itself in a number.