Each of us has a unique brain imprint, just like “fingerprints.”

An EPFL scientist has identified the signs of brain activity that make up our brain imprint, which, like a normal fingerprint, is unique.

“I think about it every day and dream about it at night. For five years now, it’s been my whole life,” says Enrico Amico, a scientist and SNSF Ambizione Fellow at the EPFL Medical Imaging Laboratory and the EPFL Neuroprosthetics Center.

He talks about his research on the human brain in general and brainprinting in particular. He has found that each of us has a “fingerprint” of the brain and that this fingerprint is constantly changing over time. His findings have just been published in the journal Science Advances.

“My research examines the networks and connections in the brain, especially the connections between different areas, to better understand how things work,” Amico says.

“We do this mainly with magnetic resonance imaging, which measures brain activity over a period of time.”

His research team processes the images to create graphs presented as colorful matrices that summarize the subject’s brain activity.

This type of modeling is known in scientific circles as network neuroscience or brain connectomics.

“All the information we need is contained in these graphs, which are known as ‘functional brain connectomes.’ Connectoms are a map of the neural network.

They inform us what the subjects were doing during the fMRI – for example, whether they were resting or doing some other task. Our connectomes change depending on what activities were performed and what parts of the brain were used,” Amico says.

Two scans are enough.

A few years ago, neuroscientists at Yale University who studied these conectomies discovered that each of us has a unique brain imprint.

By comparing graphs from MRI scans of the same subjects a few days apart, they were able to correctly match two scans of the same subject almost 95 percent of the time. In other words, they were able to accurately identify a person from their brainprint.

“This is really impressive because the identification was done using only functional connectomes, which are essentially sets of correlation scores,” Amico says.

He decided to take this finding one step further. In previous studies, brain fingerprints were identified using MRI scans that lasted several minutes. But he wondered whether these prints could be identified after just a few seconds, or if there was a specific point in time when they appear – and if so, how long would that moment last? “Until now, neuroscientists have identified brain fingerprints using two MRI scans taken over a fairly long period. But do the fingerprints actually appear after just five seconds, for example, or do they need longer? And what if fingerprints of different brain areas appeared at different moments in time? Nobody knew the answer. So, we tested different time scales to see what would happen,” says Amico.

A brain fingerprint in just 1 minute and 40 seconds

His research group found that seven seconds wasn’t long enough to detect useful data, but that around 1 minute and 40 seconds was. “We realized that the information needed for a brain fingerprint to unfold could be obtained over very short time periods,” says Amico. “There’s no need for an MRI that measures brain activity for five minutes, for example. Shorter time scales could work too.” His study also showed that the fastest brain fingerprints start to appear from the sensory areas of the brain, and particularly the areas related to eye movement, visual perception and visual attention. As time goes by, also frontal cortex regions, the ones associated to more complex cognitive functions, start to reveal unique information to each of us.

The next step will be to compare the brain fingerprints of healthy patients with those suffering from Alzheimer’s disease. “Based on my initial findings, it seems that the features that make a brain fingerprint unique steadily disappear as the disease progresses,” says Amico. “It gets harder to identify people based on their connectomes. It’s as if a person with Alzheimer’s loses his or her brain identity.”

Along this line, potential applications might include early detection of neurological conditions where brain fingerprints get disappear. Amico’s technique can be used in patients affected by autism, or stroke, or even in subjects with drug addictions. “This is just another little step towards understanding what makes our brains unique: the opportunities that this insight might create are limitless.”

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