ISCA Workshop on Plasticity in Speech Perception (PSP2005)
Senate House, London, UK
In this study we investigate an influential theory which claims that developmental disorders of higherlevel cognitive processing, in particular Specific Language Impairment (SLI), is caused by a deficit in the speed of auditory processing (a domain-general account, Tallal, et al.,1985). Previous research using behavioural techniques reveals contradictory results and indicates that at least some SLI children do not have auditory deficits. Instead their deficits appear to be restricted to the grammatical system (a domain-specific account, van der Lely, 2005). We use a neuroimaging technique that has the required excellent temporal resolution, event-related potentials (ERP) to illuminate this controversy. We aim, first to define the neural correlates (temporal, amplitude and topography) of auditory evoked potentials (AEPs: N1, P2, N2 and P3) in children with SLI. Second, we aim to define age-related changes of these neurophysiological markers in typically and atypically developing individuals. We utilized highresolution electroencephalography (Electrical Geodesic Inc, 128 electrodes) to investigate auditory ERPs from different groups: adults (18-38 years old), G(rammatical) SLI children (10-22 years old, for selection criteria see van der Lely, 2005), age match controls (matched with G-SLI children on sex, age, laterality and non-verbal IQ), and 7-8 years old language match controls (matched with the G-SLI group on receptive vocabulary). A classical auditory oddball paradigm was used with two pure tones: standard tones (1000 Hz, 80 %) and target tones (2000 Hz, 20%) with a stimulus onset asynchrony of 800 ms (SOA). Participants were asked to detect the target tones and to press a button as quick as possible. During the seven-minute period of stimulation, participants were asked to look at pictures of animals presented visually. The resulting auditory evoked potentials from all groups showed an N1 after about 100 ms followed by a P2 around 180 ms for both tones, and a P300 component for the target tones. Decrease in latencies and increase in amplitudes revealed a maturation of the auditory system. Furthermore, qualitative differences in the auditory evoked potentials were recorded from the younger children (7-8 years old) with a prominent N2 component for the standard tones (Johnstone, et al., 1996). More importantly, children with G-SLI revealed age-appropriate waveforms for the N1/P2 complex and the P300 component. Our results indicate that G-SLI children do not show a deficit in the discrimination of pure tones. We discuss the implications of our results for disentangling the domain-general vs. domain-specific hypotheses of SLI.
Bibliographic reference. Fonteneau, Elisabeth / Lely, Heather van der (2005): "Auditory neurophysiological signatures of tone discrimination in children with SLI", In PSP2005, 163 (abstract).