Do you find it difficult to spot a face in the crowd? Now we know why: people with face blindness seem to have a missing “hub” of brain connections. The discovery could be used to diagnose children with the condition, and teach them new ways to identify faces.
People with prosopagnosia, which often runs in families, cannot easily tell faces apart. This can have a significant impact on people’s lives. People with the condition rely heavily on voice recognition, clothes, hairstyle and gait to identify people, but can still fail to recognise family and friends. It can lead to social anxiety and depression, and can often go undiagnosed for many years.
Face processing isn’t a function of a single brain region, but involves the coordinated activity of several regions. To investigate what might be causing the problem, at Ben-Gurion University of the Negev, Israel, and her colleagues scanned the brains of 10 adults who have reported life-long problems with face processing. They also scanned 10 adults without the condition.
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During the scan, participants were shown sets of images of emotional, neutral, famous and unfamiliar faces. During the task they were asked to press a button when two consecutive images were identical. Some of the images also included buildings, which people with face blindness do not have any trouble identifying – these acted as a control.
Silent hubs
The team was particularly interested in the neural conversations happening in regions towards the back of the brain that we use to process basic visual information about a face, as well as regions in the front that process higher level information, such as recognising emotion in faces, pulling up memories associated with a face, or naming a face.
In people without prosopagnosia, the team found that regions towards the front of the brain form a “hub” that is highly connected with other regions, including those at the back that process more basic visual information – it’s a bit like a busy airport, says Avidan
But in people with prosopagnosia the situation was a little bit different. They were missing this hub-like behaviour. They also had a greater number of connections in the back portions of the brain.
This hyper-connectivity at the back of the brain might be a compensatory mechanism, says Avidan. “Because the hub-like behaviour is impaired, maybe they rely more on basic visual information and therefore build up more connections in the regions that are responsible for this,” she says.
This hyper-connectivity also correlated with the extent of the deficit. Not everyone with prosopagnosia has the same degree of face blindness – those who were better at face recognition showed a greater number of connections in this region.
Better diagnosis
There is huge variability in face processing in the general population, so it would be valuable to have a neural fingerprint of a prosopagnosic brain, says Avidan. “It might lead us to the point where we can scan the brain of a child who has family with prosopagnosia, examine their connectivity and determine the chances that they too will develop the condition.”
Early research suggests that training techniques . Being able to diagnose the condition early would be valuable – studies suggest that the earlier you attempt to teach people new techniques, the more likely they are to be of use.
Sensitive neural measures that could be used with children would be useful, says , who studies prosopagnosia at Dartmouth College in New Hampshire. “But we still don’t have neural measures that can be used to confidently categorise an adult as prosopagnosic, so I expect it’ll be a long time before we can do it with kids,” he says.
Avidan agrees that more studies are necessary for accurate diagnosis in children and adults.
Reference: Biorxiv, DOI:
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