Just as the arches and swirls of a fingerprint are unique to a person, so are the thousands upon thousands of links between regions of her brain. As few as 40 of these links can identify an individual with 98 percent accuracy, new findings suggest.

Researchers presented the unpublished results yesterday at the 2018 Society for Neuroscience annual meeting in San Diego, California.

The findings may make measuring functional connectivity — how often pairs of brain regions communicate — easier and more reliable, says Lisa Byrge, a postdoctoral researcher in Dan Kennedy’s lab at Indiana University Bloomington who did the work.

Researchers commonly analyze functional brain connectivity by dividing the brain into 360 regions. This process yields a matrix of more than 64,000 connections.

“Functional connectivity matrices are really huge,” Byrge says. “There’s lots of things we can do better and more confidently if we reduce the amount of data.”

Distinctive designs:

Using data from 421 brains in the Human Connectome Project, the team identified the connections that vary most from one person to the next but remain the same across repeated scans of the same person. Most of these links are part of the frontoparietal and default mode networks, which are involved in complex cognition and self-reflection, respectively.

In another set of 414 brains, the researchers showed that just 40 of these unique connections can distinguish one person from another.

When the researchers selected connections at random in the brains, they found that only about 350 of them are needed to distinguish one brain from another. This result suggests that individual differences are distributed throughout the brain.

“There’s no particular network or connection that we need” for a recognizable brain fingerprint, Byrge says.

The researchers then used the partial-fingerprint method with connectivity data from 19 people with autism and 29 controls. As before, they used half of the combined sample to define the most unique connections, and the other half to test how many of those connections are necessary to identify an individual.

They found that they could distinguish individuals based on less than 0.5 percent of the connections.

The results also have implications for studies of group differences in brain connectivity, such as those comparing autistic people with controls. In those studies, researchers need to carefully consider how to account for individual variability within each group, Byrge says.

For more reports from the 2018 Society for Neuroscience annual meeting, please click here.

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