A new study sheds light on the perception of faces among humans

The researchers make a differential diagnosis between the function and connectivity of the core areas and the areas of the extended face processing network in the defect called 'congenital prosopagnosia'

A new study, recently published in the journal Cerebral Cortex, sheds light on the perception of faces, which is apparently the most developed visual ability that humans have, because faces are a special visual category of evolutionary and social importance.

At the neural level, there is much evidence that the activity of several areas, belonging to a distributed brain network, which includes core areas located in posterior parts of the brain and extended areas, located in frontal brain areas, is necessary to ensure proper processing of faces in humans.

The new study, by a group of researchers led by Dr. Galia Avidan from the Department of Psychology at Ben-Gurion University of the Negev, makes a differential diagnosis between the function and connectivity of the core areas and areas of the extended face processing network in the defect called 'congenital prosopagnosia', which is characterized by significant difficulty in processing and recognizing faces, which is Congenital and not associated with head injury or any obvious brain damage. Dr. Avidan's partners in the research are: Michal Tanzer, PhD student in the Department of Psychology at Ben-Gurion University, Dr. Padilla Hadge-Boisin, Dr. Ning Liu and Prof. Leslie Ungerleider from the National Institutes of Health (NIH) in the USA, and Prof. Marilyn Behrman From Carnegie-Mellon University in the USA, you have a long-standing research collaboration with Dr. Avidan on congenital prosopagnosia.

Visual recognition of a face is, apparently, a process that is carried out without effort for most people, but this process is extremely difficult for people who suffer from an impairment called "prosopagnosia". Acquired prosopagnosia occurs following a head injury in adulthood, usually an injury involving the core areas. This defect, which was studied for the first time already in the middle of the last century, serves as a "unique window" to examine the psychological and neural basis of face perception. In recent years, scientific attention has been directed to another defect called congenital prosopagnosia. People suffering from this defect have a significant difficulty in processing and recognizing faces which is congenital and is not related to a head injury or any obvious brain damage. Therefore, these people provide a unique research angle that makes it possible to study the mechanisms that underlie a normal visual perception of a face.
Dr. Avidan: "In previous studies, through behavioral experiments, we showed that people with congenital prosopagnosia have a significant difficulty in a broad range of abilities related to face processing. However, despite these difficulties, and contrary to the accepted research hypotheses, studies we performed using functional magnetic resonance imaging (fMRI) consistently revealed normal activity in the core areas of the face processing network in these people."
In their current study, the researchers tried to learn more about the brain basis of the impairment and showed that in people with congenital prosopagnosia, the core areas of the face network are not effectively linked to the extended areas of this network, which process the identity of the face ("Who is the person I'm looking at"). This, in contrast to the connectivity of the core areas to other areas such as the amygdala area, which processes the emotion expressed in the face ("What is the emotion expressed by the person I'm looking at"), an ability that is normal in people with innate prosopagnosia.
"These findings," notes Dr. Avidan, "demonstrate that the significant difficulty among people with congenital prosophogenesis does not stem from abnormal functioning of the core areas, but rather from a problem with the connectivity and the transfer of information between the normal core areas and certain areas found in the extended network and related to facial identity processing. These converging evidences allow the definition of this impairment as arising from a problem in the connectivity between areas, and not from a local problem related to the functioning of certain areas as was commonly assumed in the past. It is also important to note that a similar explanation was recently also given for other neurodevelopmental defects such as congenital dyslexia. In particular, similar to congenital prosopagnosia, it is claimed that the neural basis for this disorder is related to abnormal connectivity between several brain areas that participate in the reading process."