Developmental Trajectories of Letter and Speech Sound Integration During Reading Acquisition.

Iliana I Karipidis,Silvia Brem,Gorka Fraga-González,Georgette Pleisch,Sarah V Di Pietro

doi:10.3389/fpsyg.2021.750491

Iliana I Karipidis, Silvia Brem + Show 3 more

Open Access

https://doi.org/10.3389/fpsyg.2021.750491

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Abstract

Reading acquisition in alphabetic languages starts with learning the associations between speech sounds and letters. This learning process is related to crucial developmental changes of brain regions that serve visual, auditory, multisensory integration, and higher cognitive processes. Here, we studied the development of audiovisual processing and integration of letter-speech sound pairs with an audiovisual target detection functional MRI paradigm. Using a longitudinal approach, we tested children with varying reading outcomes before the start of reading acquisition (T1, 6.5 yo), in first grade (T2, 7.5 yo), and in second grade (T3, 8.5 yo). Early audiovisual integration effects were characterized by higher activation for incongruent than congruent letter-speech sound pairs in the inferior frontal gyrus and ventral occipitotemporal cortex. Audiovisual processing in the left superior temporal gyrus significantly increased from the prereading (T1) to early reading stages (T2, T3). Region of interest analyses revealed that activation in left superior temporal gyrus (STG), inferior frontal gyrus and ventral occipitotemporal cortex increased in children with typical reading fluency skills, while poor readers did not show the same development in these regions. The incongruency effect bilaterally in parts of the STG and insular cortex at T1 was significantly associated with reading fluency skills at T3. These findings provide new insights into the development of the brain circuitry involved in audiovisual processing of letters, the building blocks of words, and reveal early markers of audiovisual integration that may be predictive of reading outcomes.

Highlights

Reading is acquired over the course of many years and extensive practice is required to achieve fluent and efficient text reading competence and comprehension skills
We found a significant main effect of congruency that was characterized by stronger blood oxygen level dependent (BOLD) responses for incongruent than congruent pairs in the left inferior frontal gyrus (IFG) and left ventral occipitotemporal cortex (vOTC) across all time points (Figure 4A)
We investigated whether audiovisual integration at each time point, reflected by the incongruency effect, was associated with familial risk for dyslexia, letter knowledge at T1 and reading outcomes at T3

Summary

Introduction

Reading is acquired over the course of many years and extensive practice is required to achieve fluent and efficient text reading competence and comprehension skills. Alphabetic writing systems are based on the principle that each speech sound corresponds to one or a combination of printed characters, namely letters. This process of mapping speech sounds to letters is taught at the very beginning of formal reading instruction and is a prerequisite for decoding sublexical units, such. During letter-speech sound processing, expert readers of transparent and semi-transparent alphabetic systems have been found to engage superior temporal brain areas more strongly when speech sounds are paired with congruent letters compared to incongruent letters (Raij et al, 2000; van Atteveldt et al, 2004; Blau et al, 2009). A similar congruency effect was observed in the Heschl’s gyrus of 9-year-old typical readers (Blau et al, 2010), while adolescent readers with typical reading skills showed the opposite pattern, characterized by stronger responses for incongruent than congruent print-speech pairs in the left superior temporal gyrus (STG; Kronschnabel et al, 2014)

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