when she got to something like ‘That’s a dog,’” he says, “she
could add that information to a huge body of knowledge.”
If these ideas about the brain’s feedback are correct, they
could show up in MICrONS’s detailed map of a brain’s form
and function. The map could demonstrate what tricks the neu-
ral circuitry uses to implement prediction and learning. Even-
tually, new AI applications could mimic that process.
Even then, however, we will remain far from answering all
the questions about the brain. Knowing neural circuitry won’t
teach us everything. There are forms of cell-to-cell commu-
nication that don’t go through the synapses, including some
performed by hormones and neurotransmitters floating in the
spaces between the neurons. There is also the issue of scale. As
big a leap as MICrONS may be, it is still just looking at a tiny
piece of cortex for clues about what’s relevant to computation.
And the cortex is just the thin outer layer of the brain. Critical
command-and-control functions are also carried out by deep-
brain structures such as the thalamus and the basal ganglia.
The good news is that MICrONS is already paving the way
for future projects that map larger sections of the brain.
Much of the $100 million, Vogelstein says, is being spent
on data collection technologies that won’t have to be invented
again. At the same time, MICrONS teams are developing
faster scanning techniques, including one that eliminates the
need to slice tissue. The Carnegie Mellon group, working with
teams at Harvard, MIT, and the Woods Hole Oceanographic
Institution, has devised a way to uniquely label each neuron
with a “bar-coding” scheme and then view the cells in great
detail by saturating them with a special gel that very gently
inflates them to dozens or hundreds of times their normal size.
“So the first cubic millimeter will be hard to collect,”
Vogelstein says, “but the next will be much easier.”
M. Mitchell Waldrop is a freelance writer in Washington, D.C. He
is the author of Complexity and The Dream Machine and was
formerly an editor at Nature.
On these pages: The colorized cubes are useful in 3-D illustrations of
various neuronal structures and processes, giving scientists their most
detailed map yet of what actually happens in the brain. C O