Cubic millimeter fragment of human brain reconstructed at nanoscale resolution

Using more than 1.4 petabytes of electron microscopy (EM) imaging data, researchers have generated a nanoscale-resolution reconstruction of a millimeter-scale fragment of human cerebral cortex, providing an unprecedented view into the structural organization of brain tissue at the supracellular, cellular, and subcellular levels. The human brain is a vastly complex organ and, to date, little is known about its cellular microstructure, including the synaptic and neural circuits it supports. Disruption of these circuits is known to play a role in myriad brain disorders. Yet studying human brain samples in such great detail comes with a host of challenges, ranging from technological limitations to the availability and preservation of tissue samples from healthy individuals. Here, Alexander Shapson-Coe and colleagues performed a high-resolution EM reconstruction of the ultrastructure of a cubic millimeter of human temporal cortex. According to the authors, the reconstruction contains roughly 57,000 cells, about 230 millimeters of blood vessels, and nearly 150 million synapses, comprising 1400 terabytes of data. Shapson-Coe et al. generated a three-dimensional reconstruction of nearly every cell and process in the cubic millimeter sample and developed a freely available tool for visualizing and analyzing the vast dataset. Using the data, the authors discovered previously underappreciated aspects of the human temporal cortex, including the disproportionate number of glia over neurons and the existence of rare yet powerful axonal inputs that contain up to ~50 synapses. “Further studies using this resource may bring valuable insights into the mysteries of the human brain,” Shapson-Coe et al. write.