traced mouse neurons
traced mouse neurons

Image of the Day: Brain Map

Scientists traced 1,000 neurons through the mouse brain, uncovering new details about how the organ is wired.

Nicoletta Lanese
Sep 6, 2019

ABOVE: Traced mouse neurons

A new map of the mouse brain traces the zig-zagging pathways of 1,000 neurons through the intricate organ, researchers reported yesterday (September 5) in Cell. To compile the map, the research team, known as MouseLight, first delivers a modified virus into the brain that causes a few dozen neurons to glow. Using a light microscope, the investigators snap 20,000 pictures of the highlighted cells. Computer algorithms help the scientists to assemble the snapshots into a cohesive map and trace the 3-D paths of individual neurons. 

“It’s by far the largest digital collection of such neurons,” says coauthor Jayaram Chandrashekar, the MouseLight scientific operations manager at the Howard Hughes Medical Institute’s Janelia Research Campus, in an announcement.

In 2018, the team used a smaller version of its dataset to reveal specific motor pathways in mice—networks of neurons that help control movement. They are now working to trace the neurons winding through structures known as the subiculum, hypothalamus, and thalamus. The researchers continue to develop their dataset in hopes of rendering a clearer picture of the mouse brain, an organ that contains about 70 million neurons on average. With 1,000 down, they have plenty more to go. 

This video layers newly traced neurons one at a time, and the counter keeps track of the total length of mapped neurons.

J. Winnubst et al., “Reconstruction of 1,000 projection neurons reveals new cell types and organization of long-range connectivity in the mouse brain.” doi:10.1016/j.cell.2019.07.042, Cell, 2019.

Nicoletta Lanese is an intern at The Scientist. Email her at