Electrophysiological studies of face processing in Williams syndrome

Williams Syndrome (WMS) is a genetically based disorder characterized by pr onounced variability in performance across different domains of cognitive f unctioning. This study examined brain activity linked to face-processing ab ilities, which are typically spared in individuals with WMS. Subjects watch ed photographic pairs of upright or inverted faces and indicated if the sec ond face matched or did not match the first face. Results from a previous s tudy with normal adults showed dramatic differences in the timing and distr ibution of ERP effects linked to recognition of upright and inverted faces. In normal adults, upright faces elicited ERP differences to matched vs. mi smatched faces at approximately 320 msec (N320) after the onset of the seco nd stimulus. This "N320" effect was largest over anterior regions of the ri ght hemisphere. In contrast, the mismatch/match effect for inverted faces c onsisted of a large positive component between 400 and 1000 msec (P500) tha t was largest over parietal regions and was symmetrical. In contrast to nor mal adults, WMS subjects showed an N320-mismatch effect for both upright an d inverted faces. Additionally, the WMS subjects did not display the N320 r ight-hemisphere asymmetry observed in the normal adults. WMS subjects also displayed an abnormally small negativity at 100 msec (N100) and an abnormal ly large negativity at 200 msec (N200) to both upright and inverted faces. This ERP pattern was observed in all subjects with WMS but was not observed in the normal controls. These results may be linked to increased attention to faces in subjects with WMS and might be specific to the disorder. These results were consistent with our ERP studies of language processing in WMS , which suggested abnormal cerebral specialization for spared cognitive fun ctions in individuals with WMS.