Abstract

Lateral temporal measures of the auditory evoked potential (AEP) including the T-complex (positive Ta and negative Tb), as well as an earlier negative peak (Na) index maturation of auditory/speech processing. Previous studies have shown that these measures distinguish neural processing in children with typical language development (TD) from those with disorders and monolingual from bilingual children. In this study, bilingual children with Turkish as L1 and German as L2 were compared with monolingual German-speaking children with developmental language disorder (DLD) and monolingual German-speaking children with TD in order to disentangle effects of limited language input vs. reduced perceptual abilities in the processing of speech and non-speech stimuli. Sensory processing reflected by the T-complex (or from lateral temporal electrode sites) was compared in response to a German vowel and a sine-wave tone in the three groups of children, ages 5 through 6 years. Stimuli were presented while children watched a muted video. Auditory evoked potentials (AEPs) were time-locked to the vowels and tones. AEPs to the frequent (standard) stimuli within an oddball paradigm were analyzed at the left (T7) and right (T8) temporal electrode sites.The results revealed language status (monolingual, bilingual, and DLD), stimulus (vowel and tone), and language test measures (receptive and expressive) all influenced the T-complex amplitudes. Particularly, the peak amplitude of Ta was modulated by language status and stimulus type. Bilingual children had significantly more negative Ta responses than the monolingual children with TD for both vowels and tones while DLD children differed from TD children only for the vowel stimulus. The amplitude of the T-complex was overall more negative at the left than at the right site. The Na peak latency was longer for the bilingual group than that observed for the two monolingual groups. The Tb latency was shorter for DLD and bilingual groups than that for TD children in the vowel condition, but no such latency difference between DLD and bilingual children was found. We suggest that the attenuated T-complex for bilingual children indicates continued plasticity of the auditory cortex to allow for learning of novel, second-language speech sounds.

Highlights

  • It has been well-documented in the literature that children are born with the ability to distinguish and categorize most speech sounds from any of the world’s languages

  • This study investigates a lesser-studied bilingual group of children, namely Turkish-German children living in Germany

  • Visual inspection revealed that the amplitude measures of T7 and T8 differed

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Summary

Introduction

It has been well-documented in the literature that children are born with the ability to distinguish and categorize most speech sounds from any of the world’s languages. Neurobiological studies of speech and language have begun to reveal how intrinsic and environmental factors modulate the development of the child’s phonological system (e.g., Kuhl, 2010; Shafer et al, 2011b; Yu et al, 2019). This study is concerned with investigating and comparing the phonological processing of three groups of children (monolingual, bilingual, and with language disorder) using a neural measure suited to analyzing the processing of fine-grained auditory detail (Tcomplex). This study investigates a lesser-studied bilingual group of children, namely Turkish-German children living in Germany. For these children, Turkish is the L1 and German is the L2

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