An innovative method to assess the receptive vocabulary of children with cerebral palsy using event-related brain potentials
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This single-case, multiple-control study illustrates the clinical use of ERPs as part of the linguistic and cognitive assessment of individuals who are unable to provide verbal or motor responses due to their multiple handicaps. The single-word receptive vocabulary of a 17-year-old patient with Cerebral Palsy (CP) and three age-matched controls was measured using an event-related potential (ERP) paradigm. The Peabody Picture Vocabulary Test-Revised (PPVT-R) was adapted for computer presentation, with three levels of difficulty (Preschool, Child, Adult). Individual pictures were presented successively, and correctly (congruent) or incorrectly (incongruent) named auditorially. ERP components were derived for both the congruent and incongruent picture-word pairs. As predicted, the N400 ERP component had a higher peak for the incongruent picture-word pairs at the Preschool and Child levels. At the Adult level, the ERP pattern was reversed (higher peak in congruent condition) for the CP patient and for two of the three controls and, it was substantially attenuated for the third control. These ERP findings indicated that picture-word pairs within the range of acquired receptive vocabulary were identified as correct or incorrect but picture-word pairs above an individual's level could not be differentiated as clearly. The findings demonstrate the clinical application of this paradigm to assessing receptive vocabulary in motor- and communication-impaired patients.
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