The human brain is a magnificently complex information-processing machine that is extremely off-limits to certain kinds of research.
Science survived the moral void into which brain research fell for much of the 20th century; and, for exceptionally valid ethical reasons, there are now stringent rules governing what researchers are allowed to do with human brains that humans are still very much using.
What scientists can do is grow little bits of one in a dish.
These tiny, three-dimensional clumps of human neural tissue, called brain organoids, aren't whole brains reproduced in a miniaturized form.
But they do reproduce enough of the brain's cellular architecture and electrical activity to give scientists a way to investigate things they could never ethically poke, prod, wire up, and repeatedly zap inside a living person's skull.
Now, a team led by neuroscientist Yoshiho Ikeuchi of the University of Tokyo has grown several such organoids, joined them up in a network, and watched as they 'learned' to distinguish which of their fellows was sending them signals.
"Together, these results demonstrate that repeated input to an organized modular network can rewire organoids generated under identical conditions into functionally differentiated modules," the researchers write, "thereby generating task-relevant heterogeneity that underlies consistent functional enhancement in vitro."
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