Hyperfamiliarity for faces: Preserved core face processing with altered medial temporal lobe connectivity in a single case study

Hyperfamiliarity for faces (HFF) is a rare condition in which unfamiliar faces evoke an abnormal sense of familiarity. We present a case study of Nell, a 49-year-old woman who developed hyperfamiliarity following a severe migraine. Using a combination of behavioural and neuroimaging approaches, we investigated the cognitive and neural mechanisms underlying her condition. Behaviourally, Nell demonstrated accurate recognition of famous and personally familiar faces, but frequently misclassified unfamiliar faces as familiar. Structural MRI scans revealed no overt abnormalities, and functional imaging showed a typical pattern of face-selective activation within the core face-processing regions. To probe familiarity-related neural responses, Nell viewed movie clips from Game of Thrones, a series she had never seen. A whole-brain analysis showed that neural activity in her medial temporal lobe (MTL) more closely resembled control participants who were familiar with the series than those who were unfamiliar. Moreover, functional connectivity analyses revealed that her core face-processing regions exhibited connectivity patterns with the MTL that were similar to familiar controls. These findings suggest that HFF may arise from atypical functional connectivity between the core face network and memory-related regions in the MTL, leading to a spurious sense of familiarity in the absence of recognition. This case offers novel insights into the neural systems supporting face familiarity and highlights the dissociability of familiarity and identification processes in face perception.