A Shared Neural Code for Recognizing Familiar Faces

Article: How Shared Neural Codes Help Us Recognize Familiar Faces
Source: Dartmouth College 
Published: November 5, 2021
Article: Brain’s Response to Familiar Faces Draws on Shared Neural Code for Visual, Social, and Semantic Processing
Source: Genetic Engineering & Biotechnology News 
Published: November 5, 2021

Neural activity in brain areas involved in social cognition
(top) and visual facial recognition (bottom)

The ability to recognize familiar faces is important in shaping social interaction. Scientists wondered whether there is a shared neural code for recognition of visually and personally familiar faces across the brains of individuals who know each other. The study recruited 14 graduate students from the same PhD program (who had known each other for at least two years) and obtained fMRI data of their brain activity in three sessions. The researchers used two methods to study face and identity perception: hyperalignment and between-subject classifiers. Hyperalignment aligns participants' brain activity to a common representational space to allow for comparing of similarities between participants. Between-subject multivariate decoding uses machine learning to predict what stimuli a participant is looking at based on the brain activity of other participants, here serving as a direct test for the presence of shared information across the brains of different participants. In two of the fMRI tasks, participants were presented images of four other personally familiar graduate students and four visually familiar people unknown to them. In a third task, participants watched parts of a movie. Hyperalignment and between-subject classifiers were applied to this data.

The results showed that the identity of visually familiar faces was decoded with accuracy in brain areas involved in visual processing of faces (e.g., the occipital face area and the fusiform face area). However, the identity of personally familiar faces was decoded with accuracy in brain areas involved in both visual processing and social cognition; these additional brain areas include the dorsal medial prefrontal cortex (processes other people's intentions), the precuneus (personally familiar faces), the insula (emotions), and the temporal parietal junction (social cognition, theory of mind). Stated differently, the identity of both visually and personally familiar faces could be decoded across participants from brain activity in visual areas, but only the identity of personally familiar faces could be decoded in areas involved in social cognition. One of the authors of the study remarks, “It would have been quite possible that everybody has their own private code for what people are like, but this is not the case. Our research shows that processing familiar faces really has to do with general knowledge about people.” In other words, individually distinct information about faces is encoded in brain activity that is shared across brains. The researchers next plan to investigate how shared person knowledge maps onto psychological dimensions and the role of individual differences in mapping shared representational space. First author of the study states, “Our findings and methodological approach might help elucidate impairments in social interactions for some classes of disorders.”

My rating of this study: ⭐⭐

Visconti di Oleggio Castello M, Haxby JV and Gobbini MI. "Shared neural codes for visual and semantic information about familiar faces in a common representational space." PNAS.  118(45):e2110474118. 9 November 2021. https://doi.org/10.1073/pnas.2110474118