Brain-wide inter-areal connectivity has been probed using bulk injections of anterograde and retrograde tracers ( Gerfen and Sawchenko, 1984 Hunnicutt et al., 2014 Luppi et al., 1990 Markov et al., 2014 Oh et al., 2014 Veenman et al., 1992 Zingg et al., 2014) and functional imaging methods with millimeter-scale spatial resolution ( van den Heuvel and Hulshoff Pol, 2010). ![]() 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.Ī core goal of modern neuroscience is to map neural circuits across the entire brain, as long-range connectivity dictates how information flows between brain regions ( Bohland et al., 2009). The method can now be used to generate a comprehensive database of neurons and their long distance connections. 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.Įconomo, Clack et al.’s advance can uncover how neurons communicate over long distances with an unprecedented level of precision. 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. ![]() ![]() now demonstrate such a method for three-dimensional imaging of tissue samples as large as the whole mouse brain. 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. 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.Ī mouse brain contains approximately 70 million neurons, and tracing the axons of many neurons within a brain is a challenging problem. 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. Nerve cells or neurons transmit electrical impulses to each other over long distances.
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