Tracking neurons across the brain
A new automated method images the entire mouse brain in enough detail to show individual nerve fibers.
Nerve cells (neurons) transmit electrical impulses to each other over long distances. These signals travel through highly branching nerve fibers called axons, which are about one hundred times thinner than a human hair, and can extend across the entire brain. Tracing the axon of a neuron from start to end can help to explain how individual neurons and brain areas communicate signals over long distances.
A mouse brain contains approximately 70 million neurons, and tracing the axons of many neurons within a brain is a challenging problem. Tackling this problem requires a method for imaging entire brains in high enough detail to unambiguously resolve and follow axons from individual neurons across the brain. Michael Economo, Nathan Clack and co-workers now demonstrate such a method for three-dimensional imaging of tissue samples as large as the whole mouse brain.
This system is fully automated and works by first imaging a layer of tissue near the exposed surface of a sample, and then cutting off a slice of tissue that corresponds to the volume that has been imaged. These steps then repeat until the entire sample has been imaged; this takes about a week for a whole mouse brain and produces about 30 terabytes of images.
The advance made by Economo, Clack and co-workers can uncover how neurons communicate over long distances with an unprecedented level of precision. The method can now be used to generate a comprehensive database of neurons and their long distance connections. Such a database would aid efforts to model the roles of neural circuits in the brain, and inform the design of experiments to study brain activity during particular behaviors.
To find out more
Read the eLife research paper on which this eLife digest is based: “A platform for brain-wide imaging and reconstruction of individual neurons” (January 20, 2016).
Read a commentary on this research paper: “Whole-brain imaging reaches new heights (and lengths)”
