Congenital Prosopagnosia May Alter Neural Circuit Topology

Babies prefer to look at faces and pictures of faces over any other object or pattern. A recent study found that even fetuses in the womb will turn their heads towards dots of light shone through the mother’s skin if the dots broadly resemble a face.

Brain imaging studies show that face recognition depends on the coordinated activity of multiple brain regions. A core set of areas towards the back of the brain processes the visual features of faces, while regions elsewhere process more variable features such as emotional expressions.

Around 2% of people are born with difficulties in recognizing faces, a condition known as congenital prosopagnosia. These individuals have no obvious anatomical abnormalities in the brain, and brain scans reveal normal activity in core regions of the face processing network.

So why do these people have difficulty with face recognition?

Brain Connectivity Differences

One possibility is that the condition reflects differences in the number of connections (or “connectivity”) between brain regions within the face processing network.

To test this idea, Gideon Rosenthal, of Ben-Gurion University of the Negev, and colleagues, compared connectivity in individuals with congenital prosopagnosia with that in healthy volunteers. In the healthy volunteers, an area of the network called the anterior temporal cortex was highly connected to many other face processing regions: that is, it acted as a face processing hub.

intra-subject functional correlation

The top schematic denotes the intra-subject functional correlation, which calculates the inter-regional correlations within the brains of single individuals.
(a) The FC difference network of controls>CPs. This comparison reflects the difference between the FC correlation coefficient values of the controls compared to the group of CP individuals. The maps are presented following the application of the FDR correction (q < 0.05).
(b) Difference networks obtained from the comparison of FC in CPs>controls.
© 2017 eLife Sciences Publications Ltd. CC-BY

In individuals with congenital prosopagnosia, this hub-like connectivity was missing. Instead, a number of core regions involved in processing the basic visual features of faces, were more highly connected to one another.

The greater this “hyperconnectivity”, the more severe the individual’s face recognition difficulties.

The findings pave the way for developing imaging-based tools to diagnose congenital prosopagnosia. The same approach could then be used to investigate the basis of other neurodevelopmental disorders that are thought to involve abnormal communication within brain networks, such as developmental dyslexia.

The work was funded by the Israel Science Foundation, and National Science Foundation.

Gideon Rosenthal, Michal Tanzer, Erez Simony, Uri Hasson, Marlene Behrmann, Galia Avidan
Altered topology of neural circuits in congenital prosopagnosia
eLife 2017;6:e25069

© 2017 eLife Sciences Publications Ltd. Republished via Creative Commons Attribution license

Top Image: Alex Bellink/Flickr