Auditory event-related potentials in the study of developmental language-related disorders

This article reviews recent auditory event-related potential (ERP) studies of developmental language disorder (DLD) and dyslexia/reading disorder (RD). The possibility of using ERPs in searching for precursors of these disorders in the early development of infants at risk is also discussed. Differences in exogenous/sensory ERPs at the latency range of P1 and N1-P2 components have been reported between groups with DLD and RD and control groups. Latency differences between the groups may be related to a common timing deficit suggested by some researchers to be one of the possible underlying factors both in DLD and dyslexia. N1 amplitude group differences may be partly related to arousal/attentional factors and partly to the 'tuning' of the auditory sensory system. Mismatch negativity deviations in DLD children seem to indicate differences in sensory memory functions. Differences between the reviewed clinical groups and controls exist also in the endogenous P3 component, though less consistently in DLD children. In both clinical groups the P3 amplitudes are, in general, lower and the latencies longer compared to those in controls. These findings are discussed in terms of possible differences in higher cognitive functions that are not specific to modality. Altered hemispheric asymmetries in DLD and RD children, as compared to controls, are commonly found in many of the reviewed ERP components. Differences in ERPs of DLD and dyslexic children in comparison to controls may not reflect only maturational lag but also more fundamental processing deficiencies.