Long Covid infections may cause some people to develop difficulties recognising faces and navigational problems, according to a new study.
Previous studies have shown that infection with the coronavirus can cause a range of neurological symptoms, such as the loss of smell and taste, as well as impairments in attention and memory known as “brain fog”.
The new study, published in the journal Cortex, suggests some individuals may develop “prosopagnosia”, also known as face blindness, following symptoms consistent with Covid.
Researchers, including those from Dartmouth College in the US, assessed a 28-year-old customer service representative and part-time portrait artist identified only as Annie, who was diagnosed with Covid in March 2020.
Annie reported difficulty with face recognition and navigation shortly after her symptoms relapsed two months later.
“When I first met Annie, she told me that she was unable to recognise the faces of her family,” study lead author Marie-Luise Kieseler said in a statement.
After meeting her parents for the first time after having Covid, Annie reported that she could not recognise them.
When she walked past her parents again, her father called out to her, she said.
“It was as if my dad’s voice came out of a stranger’s face,” the 28-year-old said, adding that she now relies on voices to recognise the people that she knows.
Annie also developed “navigational deficits” after having Covid.
“The combination of prosopagnosia and navigational deficits that Annie had is something that caught our attention because the two deficits often go hand in hand after somebody either has had brain damage or developmental deficits,” study senior author Brad Duchaine said.
“That co-occurrence is probably due to the two abilities depending on neighbouring brain regions in the temporal lobe,” Dr Duchaine added.
When scientists conducted tests to assess Annie’s problems with face recognition, they discovered that she found it particularly challenging to recognise familiar faces and learning the identities of unfamiliar ones.
In one of the tests, she was sequentially presented with 60 images of celebrity faces and asked to name them.
Annie was then presented with a list of the celebrities featured in the test to see if she knew them.
She correctly identified 29pc of the 48 celebrities whom she was familiar with compared a control group of people, who could correctly identify 84pc of familiar celebrities.
In another test, where Annie was shown a celebrity’s name and then presented with images of two faces – one of a celebrity and another of someone similar.
She could identify the celebrity in 69 per cent of the 58 trials, compared to 87 per cent in the control group.
“Our results from the test with unfamiliar faces show that it wasn’t just that Annie couldn’t recall the name or biographical information of a famous person that she was familiar with, but she really has trouble learning new identities,” Dr Kieseler explained.
“It’s been known that there are broad cognitive problems that can be caused by Covid-19, but here we’re seeing severe and highly selective problems in Annie, and that suggests there might be a lot of other people who have quite severe and selective deficits following Covid,” Dr Duchaine added.
Researchers then obtained self-reported data from 54 individuals who had long Covid with symptoms for 12 weeks or more, and 32 persons who had reported that they had fully recovered from the infection.
“One of the challenges that many respondents reported was a difficulty with visualising family and friends, which is something that we often hear from prosopagnosics,” Dr Duchaine said.
The findings, researchers said, highlight the perceptual problems with face recognition and navigation that can be caused by Covid.
They call for future work to validate the findings and to understand the nature of these visual deficits and determine whether interventions are needed to reduce their impact.