Correlation between brainstem and cortical auditory processes in normal and language-impaired children.

A functional relationship between brainstem and cortical auditory processing was shown to be abnormal in children with language-based learning problems (LP). Auditory evoked potentials were used to investigate brainstem and cortical responses to the speech sound /da/. The duration of the wave V-V(n) complex of the auditory brainstem response was studied, as was the effect of noise on correlations between cortical responses to repeated stimuli. The group of LP children (n = 11) demonstrated abnormal encoding of speech sounds on both individual measures of brainstem and cortical processing; prolonged wave V-V(n) duration and pronounced susceptibility of cortical correlations to degradation by noise were both interpreted as reflecting diminished synchrony of response generator mechanisms. Furthermore, the LP group as a whole failed to demonstrate a relationship between brainstem and cortical measures that was demonstrated to be quite strong across all normal children (NL, n = 9). However, a subset of roughly three-quarters of the LP children appeared to demonstrate the normal relationship between brainstem and cortical processing, suggesting that they share a common functional connection with NL children. This relatively normal relationship between brainstem and cortical auditory processing in most LP children, as well as the exceptions to this relationship reflected by a smaller portion of LP children, may delineate different subclasses of auditory-language-based learning problems. This suggests the potential for use of these measures as diagnostic tools.