Development and plasticity of the mismatch negativity in typically developing children, children with language impairments, and adults

The processing of human speech requires the integration of brief auditory stimuli that enter the central nervous system in rapid succession. This ability has been termed rapid auditory processing (RAP). RAP skills are believed to underlie successful language acquisition, and deficits in RAP have been consistently observed in individuals with developmental language impairments (LI). These disorders and the role of RAP in language development have been the focus of much research over the past several decades. However, many questions remain regarding the etiology and remediation of developmental LIs, as well as the normal maturational mechanisms involved in language acquisition, including the role of attention in the modification of neural sound representations. The series of experiments described here investigate the relations among RAP, attention, and language ability in several populations: normal adults, children diagnosed with an LI, and children with typical language development (TLD) using the mismatch negativity response (MMN), a component of the auditory ERP waveform that reflects an automatic auditory change detection process. The impact of an auditory discrimination training program (Fast ForWord-LanguageRTM) was also investigated.;Results show that in TLD children, developmental MMN components (early and late MMN) are modulated by rate and attention in a manner similar to adults. Attention enhances auditory discrimination in TLD children, increasing auditory processing to a level that is similar to adults. The MMN components in LI children differ from TLD children, particularly in the latency of the responses, consistent with the idea of a RAP deficit underlying developmental LI. In the LI children who completed FFWD, immediate and significant gains in oral language and auditory temporal processing abilities, as well as changes in MMN responses were observed. Further, significant associations are found between behavioral and MMN measures, with the most robust and persistent relations found between behavior and MMN components elicited by paired complex tones presented at a rate in the time range that is essential for accurate speech processing (70 ms). Together, these findings facilitate a better understanding of the role of RAP in language processing, specifically with regard to maturation, attentional mechanisms, and neural plasticity.