High-speed microscope captures fleeting brain signals

When a neuron fires, calcium flows into the cell in a wave that sweeps along the cell body. Images of this infragranular neuron were obtained three times per second by two-dimensional scanning with a Bessel focus. Redder structures are deeper in the mouse cortex. (UC Berkeley images by Na Ji)

Electrical and chemical signals flash through our brains constantly as we move through the world, but it would take a high-speed camera and a window into the brain to capture their fleeting paths.

University of California, Berkeley, investigators have now built such a camera: a microscope that can image the brain of an alert mouse 1,000 times a second, recording for the first time the passage of millisecond electrical pulses through neurons.

“This is really exciting, because we are now able to do something that people really weren’t able to do before,” said lead researcher Na Ji, a UC Berkeley associate professor of physics and of molecular and cell biology.

The new imaging technique combines two-photon fluorescence microscopy and all-optical laser scanning in a state-of-the-art microscope that can image a two-dimensional slice through the neocortex of the mouse brain up to 3,000 times per second. That’s fast enough to trace electrical signals flowing through brain circuits.

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