Analyzing the Axonal Projections of Individual Neurons Across the Mouse Brain

Abstract

An essential component of the brain is the neuron, an excitable cell that receives input from and transmits information to other neurons. Interneurons have shorter axons that are limited to local circuits, while projection neurons have extensive axons that invade multiple regions and propagate information across the brain. This study explores neuronal organization and determines whether patterns exist between different axonal projections, where neurons that have similar projection patterns can be classified as the same type. We hypothesized that neurons projecting from each region can be divided into classes that target different regions nonrandomly. The data consisted of complete reconstructions for 1094 neurons in the mouse brain from the Janelia MouseLight project. Using MATLAB, we binarized and randomized the axonal pathways of neurons with somata in the Primary Motor Area, Secondary Motor Area, and Presubiculum. We then plotted the pathway differences between neuron pairs on a histogram to determine whether they are of the same type. The variance of the random distribution was significantly smaller than that of the real distribution, particularly in the deep layers of the Primary and Secondary Motor Areas. The excess right and left tails in the real data indicate neuron pairs that are more different and more similar, respectively, than expected by chance. These preliminary results suggest that neurons can be grouped into classes that each target a specific set of brain regions, based on their axonal pathways.