How the brain processes facial identity has long been a source of intrigue to neuroscientists — a visual system that instaneously distinguishes individual faces is impressive to say the least. Researchers from Carnegie Mellon University’s Department of Psychology and the Center for the Neural Basis of Cognition have had a possible breakthrough. Their findings, recently published in the Proceedings of the National Academy of Sciences, have given insights into both the computational architecture of visual recognition, and the functional organization of the brain.
According to Adrian Nestor, a postdoctoral research fellow at CMU’s Department of Psychology and the lead author of the study, “this research will change the types of questions asked going forward because we are not just looking at one area of the brain… Now, scientists will have to account for the system as a whole or else our ability to understand face individuation will be limited.”
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The study involved participants distinguishing between different faces and facial expressions, as well as between various orthographic forms (fonts) while inside a functional MRI scanner. Participants’ reactions to changes in facial expressions and letter fonts were then compared. The data revealed that a network of fusiform and anterior temporal regions activate distinct patterns for different stimuli. The ground-breaking results show that the simple task of recognizing a face is supported by a network of cortical regions that share resources with the areas involved in the processing of facial expressions and fonts.
The findings have provided insight into where processes such as individuation, expression analysis, and high-level semantic processing occur. Individuation is the process of telling faces apart across various expressions. For example, it allows you to differentiate a random elderly lady from your grandmother. The study tried to mimic this process by showing participants images of four different people with each person displaying four different expressions.
Participants had to match the images with low-level and high-level characteristics such as mean luminance and sex, as well as external features such as hair. The results suggest that face individuation relies on a distributed cortical system. Initially it was thought that individuation occurs only in the fusiform face area (FFA); however, through functional magnetic resonance imaging (fMRI) it was found that anterior temporal regions are also activated.
Figuring out how the process of facial identity works could lead to treatments for disorders such as prosopagnosia, the inability to recognize faces (also known as face blindness).
Regarding the study, co-author Marlene Behrmann, a professor of psychology at CMU and an expert in using brain mapping to study prosopagnosia remarked, “not only do we have a more clearly defined architectural model of the brain, but we were able to determine the involvement of multiple brain areas in face recognition as well as in other types of processes, such as visual word recognition.” The current study is a stepping stone to a full understanding of the operation of this system.
