Google has created the most detailed three-dimensional map yet of the connections within the human brain. And even though the entire data set they produced covers no more than a cubic millimetre (usually one pixel in an MRI scan), they have managed to obtain so much data that can only be processed after a long time, New Scientist reports.
The brain map, which is freely available online, reveals a staggering amount of detail, including patterns of connections between neurons, as well as what may be a new kind of neuron. In a cubic millimeter piece of brain that would appear as a single pixel in an MRI scan, Google examined 50,000 neurons and the hundreds of millions of spidery tendrils — extensions of neurons — that connect them, as well as roughly 130 million synapses, or cell-to-cell connections. At the end of the 3D scan, 1.4 petabytes of data was received, which equates to 1.4 million gigabytes.
Given the huge amount of data, it’s no surprise that Viren Jain, a researcher at Google Research, said they haven’t been able to pay enough attention to every detail yet. According to him, the difficulty of the task is on par with mapping the human genome, which took 20 years.
Although the researchers are still at the very beginning of analyzing the data, they have already found some interesting stuff. For example, they managed to prove wrong the earlier theory that the tendrils of one neuron can form up to 2-4 synapses with the nearby tendrils of another neuron. In this detailed sample they have found places where as many as 20 synapses formed, but they do not yet know how this is possible – it could be that these strong relationships are the basis of the learned behavior, allowing for the rapid transmission of messages.
The team also found mysterious pairs of neurons deep in the cortex that hadn’t been observed before. “The two cells pointed in exactly the opposite direction on the same axis,” says Jeff Lichtman, also at Harvard University, who initiated the entire research project before Google Research took over. For now, scientists have no clue how or why this opposite pointing occurs. For that, more mapping and data analysis would be needed.
Mapping an entire human brain would need a data set that is a further 1000 times larger, a zettabyte, which is “comparable to the amount of digital content generated in a year by the planet Earth”, according to Lichtman.
But then, going that far might not be worthwhile. “We may discover that a lot of it is coding information that came in through experience, and therefore every brain will be something different from every other one,” he says. Without understanding how information is stored, the data would make no sense. So further research has to go in that direction.