Deep connections

PROJECT PROLIFERATION To map the nanoscale connectome of C. elegans, in the 1980s, researchers led by biologist Sydney Brenner at the University of Cambridge, UK, thinly sliced the millimetrelong worms and photographed each slice using a film camera mounted to an electron microscope. The work being conducted at the Allen Institute is part ofa collaboration with researchers at Baylor College of Medicine in Houston, Texas, Princeton University in New Jersey and Harvard University in Cambridge, Massachusetts, known as Machine Intelligence from Cortical Networks, which is funded by the US government. A newer approach, known as focused ion beam scanning electron microscopy (FIB-SEM), uses a beam of charged ions to shave away a thin layer of a tissue sample. (Even the fruit-fly brain, which is roughly the size of a poppy seed, has to be chopped into smaller chunks.) A method called gas cluster ion beam scanning electron microscopy (GCIB-SEM), developed by Kenneth Hayworth, a neuroscientist at Janelia Research Campus, works similarly but has a larger field of view, which makes it more feasible for use in imaging larger brains.