"...and then it was done, and it was about half three," said the lead researcher, when asked how her team mapped every connection in a living human brain. She said this on Monday. She did not look up from her sandwich.
The map is complete. It covers all 86 billion neurons and roughly 100 trillion synapses. A synapse is the gap where one brain cell talks to the next one. There are a great many of them. The team counted every single one and then went for lunch.
Twenty-six volunteers took part. Each lay still for an afternoon while a scanner did most of the work. A control group of twenty-six more lay still with no scanner, to check that lying still does not by itself explain the mind. It does not. The chance that the result is a fluke is less than one in a thousand.
The finished map shows where memory sits, how a thought travels, and why anyone does anything at all. The researchers describe this as "fine". The full dataset runs to twenty-six petabytes. A petabyte is a lot of hard drives.
