Face and gaze processing in Prader-Willi syndrome.

A number of developmental disorders of genetic origin show atypical aspects of face processing. However, little is known about face processing in Prader-Willi syndrome (PWS). PWS is of specific interest because it has two modes of inheritance (paternally derived deletion, DEL; maternal uniparental disomy, UPD) only one of which (UPD) is associated with an increased risk of autistic symptomology. We conducted electrophysiological (ERP) and behavioural measurements of face and eye-gaze processing in individuals with PWS derived from both modes of inheritance. Our hypothesis that UPD PWS would show a pattern of deficits resembling those seen in autism was only partially confirmed. Although some individuals from both groups showed deficits, as a whole the UPD group (N=8) and the DEL group (N=8) did not differ on behavioural measures of face processing or autistic symptoms. In contrast, the effect of face orientation and gaze direction on the amplitude of the N170 ERP component differed between the two PWS sub-types. Thus, while the behavioural tests did not discriminate between the UPD and deletion forms of the syndrome, electrophysiological measures of face processing did differentiate the groups.