A locus for an auditory processing deficit and language impairment in an extended pedigree maps to 12p13.31-q14.3.

Despite the apparent robustness of language learning in humans, a large number of children still fail to develop appropriate language skills despite adequate means and opportunity. Most cases of language impairment have a complex etiology, with genetic and environmental influences. In contrast, we describe a three-generation German family who present with an apparently simple segregation of language impairment. Investigations of the family indicate auditory processing difficulties as a core deficit. Affected members performed poorly on a nonword repetition task and present with communication impairments. The brain activation pattern for syllable duration as measured by event-related brain potentials showed clear differences between affected family members and controls, with only affected members displaying a late discrimination negativity. In conjunction with psychoacoustic data showing deficiencies in auditory duration discrimination, the present results indicate increased processing demands in discriminating syllables of different duration. This, we argue, forms the cognitive basis of the observed language impairment in this family. Genome-wide linkage analysis showed a haplotype in the central region of chromosome 12 which reaches the maximum possible logarithm of odds ratio (LOD) score and fully co-segregates with the language impairment, consistent with an autosomal dominant, fully penetrant mode of inheritance. Whole genome analysis yielded no novel inherited copy number variants strengthening the case for a simple inheritance pattern. Several genes in this region of chromosome 12 which are potentially implicated in language impairment did not contain polymorphisms likely to be the causative mutation, which is as yet unknown.

Auditory language comprehension in children with developmental dyslexia: evidence from event-related brain potentials.

In the present study, event-related brain potentials (ERPs) were used to compare auditory sentence comprehension in 16 children with developmental dyslexia (age 9-12 years) and unimpaired controls matched on age, sex, and nonverbal intelligence. Passive sentences were presented, which were either correct or contained a syntactic violation (phrase structure) or a semantic violation (selectional restriction). In an overall sentence correctness judgment task, both control and dyslexic children performed well. In the ERPs, control children and dyslexic children demonstrated a similar N400 component for the semantic violation. For the syntactic violation, control children demonstrated a combined pattern, consisting of an early starting bilaterally distributed anterior negativity and a late centro-parietal positivity (P600). Dyslexic children showed a different pattern that is characterized by a delayed left lateralized anterior negativity, followed by a P600. These data indicate that dyslexic children do not differ from unimpaired controls with respect to semantic integration processes (N400) or controlled processes of syntactic reanalyses (P600) during auditory sentence comprehension. However, early and presumably highly automatic processes of phrase structure building reflected in the anterior negativity are delayed in dyslexic children. Moreover, the differences in hemispheric distribution of the syntactic negativity indicate different underlying processes in dyslexic children and controls. The bilateral distribution in controls suggests an involvement of right hemispherically established prosodic processes in addition to the left hemispherically localized syntactic processes, supporting the view that prosodic information may be used to facilitate syntactic processing during normal comprehension. The left hemispheric distribution observed for dyslexic children, in contrast, suggests that these children do not rely on information about the prosodic contour during auditory sentence comprehension as much as controls do. This finding points toward a phonological impairment in dyslexic children that might hamper the development of syntactic processes.