Temporal dynamics of facial identity and expression recognition in a developmental prosopagnosic

Facial recognition and expression recognition are encoded by distinct pathways (Haxby, Hoffman, & Gobbini, 2000). Individuals with prosopagnosia present impaired identity recognition with preserved expression recognition, supporting this view. EEG studies have found diminished amplitude of the N170 component for faces in individuals with prosopagnosia. The effect of facial expression on the face-specific N170 is still unclear, but the late positive potential (LPP) at 300ms after stimulus onset is likely to be modulated by type of emotion and emotion processing. This study aimed to confirm that participant TM – a female with developmental prosopagnosia – demonstrated a marked decrease in the N170 and to acquire the first ERPs related to emotional expression processing in an individual with prosopagnosia. Compared to 11 control participants (4 age-matched), TM presented impaired identity recognition (scores 2 standard deviations (SD) below age-matched controls) and gender discrimination (scores 4 SDs below age-matched controls). TM showed intact emotion and object recognition and emotional expression discrimination (scores <1 SD above controls). On a faces vs. houses comparison of ERPs, TM showed a smaller N170 at temporal and occipital electrodes to faces than controls, and a smaller difference between the two conditions. On a comparison of implicit (gender discrimination) vs. explicit (emotion discrimination) emotional processing task, TM’s late positive potential was not modulated by emotion or condition, an effect that controls did show. These results further support the dissociation not only between identity and emotion recognition but also gender discrimination, reflected both in behavioral measures and in ERP components.