Mapping the mouse brain, a neuron at a time
Here’s a progress report at the 1000-mark.
By tracing the paths of individual neurons, US researchers are creating this rather striking map of the mouse brain.
To date the team at the Howard Hughes Medical Institute's Janelia Research Campus has carefully untangled more than 1000 neurons, tracing each cell's branching route across the brain to pinpoint where it goes and to which cells it connects.
If laid end to end, they would stretch more than 80 metres.
"It's by far the largest digital collection of such neurons," says Jayaram Chandrashekar, who leads the project team known as MouseLight.
They aren’t realistically expecting to complete the task, as the mouse brain contains about 70 million neurons.
However, co-author Karel Svoboda suggests that 100,000 might provide “a fuzzy view of the whole brain's wiring scheme to emerge – the equivalent of a tourist map that captures major landmarks”.
Currently, it takes about one day to trace a single neuron, but a few years ago, it took a week or two.
Chandrashekar says neuroscientists have a general idea about which areas of the mammalian brain talk to one other, but not what the messaging infrastructure actually looks like.
The team began its neural cartography effort two years ago and released data on the first 300 neurons in late 2017. The updated findings are reported in a paper in the journal Cell.
The first step of the process is to inject a virus that makes a handful of neurons glow, then use a light microscope to capture high-resolution images of them.
A computer program stitches together the 20,000 resulting images to make a three-dimensional map of the brain, then algorithms and software help follow the intertwined paths of individual neurons.
The preliminary data are revealing new clues about how the mouse brain is wired. In some regions, neurons cluster into discrete categories, while in others, neurons can't be easily delineated into specific types.