 Dr. Williams's group hypothesized that prosopamnesia is caused by an inability of the FFA to maintain a stable representation of new faces long enough for them to be encoded into memory.This conclusion is partially based on the patient's differing responses to familiar and unfamiliar faces within the FFA as seen in blood-oxygen-level dependent (BOLD) responses recorded during functional magnetic resonance imaging (fMRI) tests.Within the brain, visual stimuli are processed along many different neural circuits.