Why some people can't recognise faces decoded

Berlin: The causes of congenital face blindness - a condition in which a person is unable to use facial features to identify other people - can be traced back to an early stage in the perceptual process, scientists say. Each face is unique and forms a crucial part of a person's identity and interpersonal communication, researchers said.

However, the situation is different for people with congenital prosopagnosia, or face blindness. People affected by this condition are unable to use facial features to identify the person in front of them. In everyday life, people with facial blindness are often able to compensate for this inability to recognise others by instead focusing on, for example, a person's characteristic appearance, hair style, or gait.

However, the true extent of the impairment becomes evident in social situations, when the affected person has to interact with others, or when the nature of their job means they have to be able to distinguish between and identify many different people. It is estimated that approximately one to two per cent of people are affected by this condition, researchers said. Until now, the cause of facial blindness was assumed to be associated with the later stages of the perceptual process.

These are the stages involved in converting facial information into abstract code for long-term storage. A team of researchers led by Andreas Luschow from Charite University in Berlin have been focusing their efforts on a group of persons who have experienced severe problems recognising familiar faces from a young age, but show no evidence of other cognitive impairments. "We were able to show that even the earliest face-selective responses, those recorded approximately 170 milliseconds after seeing a face, are altered in people with congenital prosopagnosia; we were also able to show that these changes are closely linked to their deficit in recognising faces," said Luschow.

Researchers, including those from Physikalisch-Technische Bundesanstalt Berlin and the University of Bamberg, used MEG (magnetoencephalography) to measure the magnetic signature of cortical activity. Results showed that even life-long contact with other people does not enable affected persons to compensate for this face recognition deficit.

This would suggest that the underlying neural mechanisms are divided into distinct, closed units, making it impossible for other areas of the brain to take over their function. The study was published in the journal PLOS ONE.