Neurophysiological indices of language impairment in children

Recent investigations of children with specific language impairment (SLI) h ave found deviant anatomical asymmetry of the perisylvian cortex. These stu dies argue that this deviant anatomical asymmetry is linked to the language disorders of SLI children. To date no studies have examined whether devian t functional asymmetry underlies the processing of spoken language in these children. In the current study, brain-electrical activity was recorded fro m 31 scalp sites while children with SLI listened to auditorally presented stories and two different nonsense contexts. Electrical activity was time-l ocked to the grammatical word "the" in these contexts. The SLI children sho wed reversed asymmetry compared to control children from 200 ms to 400 ms i n processing "the" in all contexts. More specifically, they showed depresse d processing at the left temporal scalp site (T7) and enhanced processing a t the right temporal site (T8). The second spatial derivative (the Laplacia n) of the voltage activity was calculated to remove constant voltage potent ial and uniform changes in voltage potential across the scalp. The Laplacia n analysis indicated that the sources of the positive electrical activity s een at the temporal electrode sites T7 and T8 are the lateral surfaces of t he temporal cortices. A comparison of the scalp topography of the voltage p otentials and Laplacian also suggests that children with SLI lack some cont ribution from a deep neural generator, possibly in the hippocampus or basal ganglia. This investigation is the first to demonstrate a direct link betw een deviant neurophysiological asymmetry and the processing of spoken langu age in children with SLI.