A new imaging technique developed by researchers at the University of California, Berkeley, has produced a microscope that can image the brain of a mouse 1,000 times per second—fast enough to capture 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.
With this technique, neuroscientists like Ji can now clock electrical signals as they propagate through the brain and ultimately look for transmission problems associated with disease.
One key advantage of the technique is that it will allow neuroscientists to track the hundreds to tens of thousands of inputs any given brain cell receives from other brain cells, including those that don’t trigger the cell to fire. These sub-threshold inputs — either exciting or inhibiting the neuron — gradually add up to a crescendo that triggers the cell to fire an action potential, passing information along to other neurons.
Featured image: Using a two-photon fluorescence microscope with an extra-large field of view, UC Berkeley researchers imaged neurons (green) in a large chunk of the cortex of the brain of a living mouse. The area shows neurites in a volume of 4.2 mm × 4.2 mm x 100 microns. The dark branches are blood vessels. (UC Berkeley image by Na Ji)