Letters and speech sounds associations in typical and atypical reading development : PhD thesis

Beck, Joanna

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Letters and speech sounds associations in typical and atypical reading development : PhD thesis

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Title: Letters and speech sounds associations in typical and atypical reading development : PhD thesis

Abstract:

In alphabetic languages, learning letters and speech sounds correspondence is the first and one of the most crucial steps in reading development. Research shows that this process differs depending on how transparent the language is (how constant and repetitive the association of letters and speech sounds is, e.g., Italian is highly transparent, Polish and Dutch are moderately transparent, and English is an opaque language). According to the literature, Dutch kids learn letter-speech sound (LS) associations in their first year of formal schooling. From the neuroscience perspective, we know that the left superior temporal cortex (STC) plays an essential role in LS integration. Developmental dyslexia or family risk of dyslexia are factors that may interfere with this process. The process of LS association seems similar in alphabetic languages but has not been thoroughly examined in the blind who read the Braille alphabet using their sense of touch.The principal aim of my doctoral dissertation is to investigate how the process of LS association occurs in the typical and atypical reading development in Polish. In the first behavioral experiment, I checked how much time Polish-speaking children needed to learn the correspondence between LS pairs. As it is the case with the Dutch language, children learn this skill in the first year of schooling, but it takes them longer to automate this process (up to around the third grade of primary school). In the second experiment, I delineated the brain regions that play a role in LS integration in young readers with and without a family history of dyslexia. Children's STC activity during the LS association task varied considerably between those with and without a family history of dyslexia. The at-risk group showed more robust activation when processing congruent LS pairs than incongruent ones, while the no-risk group showed the opposite pattern – higher activation for incongruent LS pairs.In the third experiment, I found significant changes in the pattern of brain activation during the first two years of education. While the brain activity decreases in response to unimodally presented speech sounds (auditory) and letters (visually), it increases when children process multimodal LS pairs.In the last experiment, I checked what the process of LS integration looks in the blind compared to the sighted. The integration process takes place in the STC in both groups. However, the activation pattern is different. The sighted subjects showed higher activity for incongruent LS pairs in the bilateral STC, similarly to children without the family risk of dyslexia in the early stages of learning to read. In the blind, congruent pairs resulted in an increased response in the right STC. These differences may be related to lower exposure to letters in the blind or more sequential processing of Braille as compared to print reading. The experiments that comprise my doctoral dissertation lead to a conclusion that the process of letter and speech sound association in Polish takes place in the STC. Its exact course is influenced by dyslexia, family risk of dyslexia, and reading modality.