A new microscope breaks a long-standing speed limit, recording footage of brain activity 15 times faster than scientists once believed possible. It gathers data quickly enough to record neurons' voltage spikes and release of chemical messengers over large areas, monitoring hundreds of synapses simultaneously—a giant leap for the powerful imaging technique called two-photon microscopy.
The trick lies not in bending the laws of physics, but in using knowledge about a sample to compress the same information into fewer measurements. Scientists at the Howard Hughes Medical Institute's Janelia Research Campus have used the new microscope to watch patterns of neurotransmitter release onto mouse neurons, they report July 29 in Nature Methods. Until now, it's been impossible to capture these millisecond-timescale patterns in the brains of living animals.
Scientists - Imaging - Opaque - Samples—like - Living
Scientists use two-photon imaging to peer inside opaque samples—like living brains—that are impenetrable with regular light microscopy. These microscopes use a laser to excite fluorescent molecules and then measure the light emitted. In classic two-photon microscopy, each measurement takes a few nanoseconds; making a video requires taking measurements for every pixel in the image in every frame.
That, in theory, limits how fast one can capture an image, says study lead author Kaspar Podgorski, a fellow at Janelia. "You'd think that'd be a fundamental limit -¬ the number of pixels multiplied by the minimum time per pixel," he says. "But we've broken this limit by compressing the measurements." Previously, that kind of speed could only be achieved over tiny areas.
Line - Angular - Projection - Microscopy - Data-collection
The new tool—Scanned Line Angular Projection microscopy, or SLAP—makes the time-consuming data-collection part more efficient in a few ways. It compresses multiple pixels into one measurement and scans only pixels in areas of interest, thanks to a device that can control which parts...
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