The first release included data from 100 injections. More data is being added every week. "We are now releasing brains on a rolling basis." Mitra says they are halfway through but it is hard to know how many injections will be needed because "mouse brains show individual variation, so building up a statistical description of the variations will require many repeats. Since no one has ever tried doing this, we don't know how many repeats we will need."
The scientists have funding until 2014 and expect to have a "reasonable first draft" of a mesoscale rodent brain connectivity map by then, Mitra says.
Kathleen Rockland, a neuroscientist at The Picower Institute for Learning and Memory at the Massachusetts Institute of Technology, praised the approach. "As a learning tool for long-distance connections and brain structures, this is superb—a combination of virtual microscope, encyclopedia and public forum, where comments and dialogue are encouraged."