Abstract
In alphabetic scripts, learning letter-sound (LS) association (i.e., letter knowledge) is a strong predictor of later reading skills. LS integration is related to left superior temporal cortex (STC) activity and its disruption was previously observed in dyslexia (DYS). Whether disruption in LS association is a cause of reading impairment or a consequence of decreased exposure to print remains unclear. Using fMRI, we compared activation for letters, speech sounds and LS association in emerging readers with (FHD+, N = 50) and without (FHD−, N = 35) familial history of DYS, out of whom 17 developed DYS 2 years later. Despite having similar reading skills, FHD+ and FHD− groups showed opposite pattern of activation in left STC: In FHD− children activation was higher for incongruent compared to congruent, whereas in FHD+ it was higher for congruent LS pairs. Higher activation to congruent LS pairs was also characteristic of future DYS. The magnitude of incongruency effect in left STC was positively related to early reading skills, but only in FHD− children and (retrospectively) in typical readers. We show that alterations in brain activity during LS association can be detected at very early stages of reading acquisition, suggesting their causal involvement in later reading impairments. Increased response of left STC to incongruent LS pairs in FHD− group might reflect an early stage of automatizing LS associations, where the brain responds actively to conflicting pairs. The absence of such response in FHD+ children could lead to failures in suppressing incongruent information during reading acquisition, which could result in future reading problems.
Highlights
In alphabetic scripts, learning the association between letters and speech sounds (LS; i.e., letter knowledge) is a critical step in reading acquisition
We examined brain response to letters, speech-sounds and LS pairs in emerging readers with and without familial risk for DYS and retrospectively assessed which of the observed effects are present in children who developed DYS 2 years later
Even though behaviorally FHD+ and FHD− groups did not differ with respect to early reading, phonological awareness and orthographic skills and the prevalence of DYS was similar between the FHD groups in children qualified for the current analyses, we found brain activation differences for both unisensory and multisensory conditions in regions previously implicated in DYS
Summary
In alphabetic scripts, learning the association between letters and speech sounds (LS; i.e., letter knowledge) is a critical step in reading acquisition. Letter-Speech Sound Integration and Dyslexia Risk most children master LS associations within 1 year of reading instruction and acquire reading effortlessly (Blomert and Vaessen, 2009). Learning letter-sound (LS) associations happens at the very start of reading acquisition or already prior to reading acquisition, the full integration of LS pairs requires practice, and might take years to become fully automated. Around 10 percent of children struggle with reading acquisition and develop persistent reading difficulties, i.e., dyslexia (DYS; Shaywitz et al, 1998). According to a recent meta-analysis, children with family history of DYS (FHD+) face challenges in acquiring letter knowledge in preschool, which might result in later reading difficulties (Snowling and Melby-Lervåg, 2016)
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