One approach to understanding the brain is to reconstruct the shapes and connections of individual neurons.
The group of mouse neurons shown in color belongs to an area of the brain called the somatosensory cortex—the area that contains a map of the body from various tactile senses, such as touch, pain, pressure, and temperature. High-resolution 3D colored models of the neurons and their connections were generated from large stacks of two-dimensional electron microscopy (EM) images. One of the original EM images is shown in gray behind the colored neurons. The entire width of the group of neurons is about that of a single human hair. The mouse brain is estimated to contain about 75 million neurons, while the human brain has about 86 billion. Mapping the brain’s connections at this level of detail, about 1 trillion times finer than a magnetic resonance imaging (MRI) scan, allows scientists to study the anatomy and function of healthy and diseased brains at the resolution of single cells and synapses.
Image courtesy of Daniel Berger, Massachusetts Institute of Technology (MIT), Cambridge, MA. (EM data from N. Kasthuri, R. Schalek, K. Hayworth, J.-C. Tapia, and J. Lichtman at Harvard University; reconstruction and rendering by D. Berger and S. Seung at MIT.)
The image was produced by automatically cutting several hundred 30-nm thick slices of mouse brain tissue. Each slice was then imaged in sequence using an electron microscope (EM)—a type of microscope that can magnify objects up to 10 million times. The stack of EM images was reconstructed in 3D and colored to better visualize individual neurons and the connections between them.