Alexis Kidder^1,2 (), Clara Sava-Segal¹, Emily Finn¹, Brad Duchaine¹, Chris Baker²; ¹Dartmouth College, ²National Institute of Mental Health

Although developmental prosopagnosia (DP) is defined by difficulty recognizing faces, the severity and specificity of this deficit varies widely, with some DPs also reporting atypical perception to other stimuli. The physiological correlates underlying this variability are largely unknown and are typically investigated by averaging univariate responses to stimulus categories within visual regions. To address these methodological constraints, we compared whole-brain neural alignment during movie-watching using pairwise inter-subject correlations (ISC). We compared inter- and intra-group neural variability in DPs (N=28) and controls (N=45) using an open fMRI dataset where participants watched Game of Thrones (GoT; Noad et al., 2024). We found that controls were more aligned than DPs in several regions within and outside visual regions, such as right early visual areas and bilateral superior temporal sulcus (STS). DPs had stronger alignment in left early visual areas. When separating participants within each group who were familiar and unfamiliar with GoT, we replicated that familiar controls had greater alignment in right STS compared to familiar DPs (Noad et al., 2024), and showed familiar DPs had greater alignment in bilateral early visual areas. Familiar controls (N=22) had the most whole-brain alignment, followed by unfamiliar controls (N=23), familiar DPs (N=13) and unfamiliar DPs (N=15). To expand on these findings, we used pairwise pattern ISC to capture changes in multivariate patterns of neural activity at every timepoint. Neural alignment dynamically changed during perception, and results indicate peak differences between groups were driven by faces conveying social information. Altogether, DPs had greater whole-brain neural variability during visual processing compared to controls. Within DPs, low-level visual regions were most similar, suggesting that increased neural variability may occur in later stages of visual processing. Future work will examine the relationship between ISC and behavioral performance to link neural variability with DP perceptual profiles.