Brain activity reflects early maturation of speech processing already in infancy
Auditory abilities and the speech processing capacity of the brain, factors central to language learning, mature to a notable degree in the first years of life. Familial risk for the reading disorder dyslexia also affects the development of auditory abilities already in infancy.

The electroencephalogram and its event-related potentials (ERPs), responses evoked by events such as sounds, provide opportunities for studying the auditory abilities important for language development already in infancy. In order to interpret the findings, understanding the typical maturation of these responses and the auditory functions that they reflect is essential.

A study recently completed under the DyslexiaBaby project at the University of Helsinki’s Faculty of Medicine investigated the development of Finnish-language speech and the responses evoked by changes in it in small children from newborns to 2.5 years of age. The project is headed by Professor of Psychology Teija Kujala at the Cognitive Brain Research Unit (CBRU).

“The number of child subjects in the study ranged from a little under one hundred to nearly 200, which can be considered a globally exceptionally large sample in ERP studies on infants,” says Paula Virtala, docent of cognitive neuroscience, who is the first author of the study.

“However, prior studies on the topic are sparse in number. Very few of them cover infancy, in spite of its vital role in early language development, let alone range from infancy to early childhood.”

Building blocks of language learning are formed by early childhood

Based on the results, neural speech processing matures markedly in the first years of life. This involves auditory abilities that are essential to language learning, such as the discrimination of speech sounds. However, these abilities are not the same in two-year-olds as in adults.

“Some speech sound features, such as duration and pitch, are processed by the child’s auditory system in a more developed, adult-like manner, while other features important to language development, such as the discrimination of acoustically similar vowels, are still undergoing heavy maturation,” Virtala says.

Familial risk for dyslexia has early effects

The study also looked into the effects of a familial risk of dyslexia on the development of neural speech processing skills from infancy to early childhood. Developmental dyslexia is a common and heritable developmental disorder that compromises reading acquisition.

“The risk of familial dyslexia was observable at the group level in neural speech sound discrimination, particularly in the evoked responses associated with sound duration and vowel changes at all age stages, that is, at birth, six months and 2.5 years,” says Virtala.

In the future, the DyslexiaBaby project will investigate, from early childhood to school age, how the deficits observed in neural speech processing related to the dyslexia risk are linked with the development of literacy skills and how they predict these skills from infancy onwards. In connection with this, the potential of musical interventions and musical activity in supporting language and literacy skills will be investigated.

The study on school-age children is part of the research activities of the Centre of Excellence for Music, Mind, Body and Brain coordinated by the University of Jyväskylä and the University of Helsinki in the term 2022–2029.

Original article: P. Virtala, V. Putkinen, L. Kailaheimo-Lönnqvist, A. Thiede, E. Partanen, T. Kujala, Infancy and early childhood maturation of neural auditory change detection and its associations to familial dyslexia risk, Clinical Neurophysiology, 2022. DOI: doi.org/10.1016/j.clinph.2022.03.005

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