Electrophysiological correlates of semantic processing in Williams syndrome

Williams syndrome (WS), a genetic neurodevelopmental disorder due to microdeletion in
chromosome 7, has been described as a syndrome with an intriguing socio-cognitive
phenotype. Cognitively, the relative preservation of language and face processing abilities
coexists with severe deficits in visual-spatial tasks, as well as in tasks involving abstract
reasoning. However, in spite of early claims of the independence of language from general
cognition in WS, a detailed investigation of language subcomponents has demonstrated
several abnormalities in lexical-semantic processing. Nonetheless, the neurobiological
processes underlying language processing in Williams syndrome remain to be clarified.
The aim of this study was to examine the electrophysiological correlates of semantic
processing in WS, taking typical development as a reference. A group of 12 individuals
diagnosed with Williams syndrome, with age range between 9 and 31 years, was
compared with a group of typically developing participants, individually matched in
chronological age, gender and handedness. Participants were presented with sentences
that ended with words incongruent (50%) with the previous sentence context or with
words judged to be its best completion (50%), and they were asked to decide if the sentence
made sense or not. Results in WS suggest atypical sensory ERP components (N100 and
P200), preserved N400 amplitude, and abnormal P600 in WS, with the latter being related
to late integration and re-analysis processes. These results may represent a physiological
signature of underlying impaired on-line language processing in this disorder
This research was supported by a Doctoral Grant (SFRH/BD/35882/2007) awarded to the first author, as well as by the
grant PIC/IC/83290/2007, both from FCT (Fundação para a Cieˆncia e a Tecnologia), in Portugal.