Zuk-Dunstan-2020

ABSTRACT

Recent efforts have focused on screening methods to identify children at risk for dyslexia as early as preschool/kindergarten. Unfortunately, while low sensitivity leads to under-identification of at-risk children, low specificity can lead to over-identification, resulting in inaccurate allocation of limited educational resources.

The present study focused on children identified as at-risk in kindergarten who do not subsequently develop dyslexia to specify factors associated with better reading outcomes among at-risk children. Early screening was conducted in kindergarten and a subset of children was tracked longitudinally until second grade. Potential protective factors were evaluated at cognitive-linguistic, environmental, and neural levels.

Relative to at-risk kindergarteners who subsequently developed dyslexia, those who did not were characterized by significantly higher socioeconomic status (SES), speech production accuracy, and microstructure of the posterior right-hemispheric superior longitudinal fasciculus (SLF). A positive association between microstructure of the right SLF and subsequent decoding skills was found to be specific to at-risk children and not observed among typical controls.

Among at-risk children, several kindergarten-age factors were found to significantly contribute to the prediction of subsequent decoding skills: microstructure of the posterior right SLF, age, gender, SES, and phonological awareness. These findings suggest that putative compensatory mechanisms are already present by the start of kindergarten. The right SLF, in conjunction with the cognitive-linguistic and socioeconomic factors identified, may play an important role in facilitating reading development among at-risk children. This study has important implications for approaches to early screening, and assessment strategies for at-risk children.

Excerpts from Full Text:

Moreover, among all at-risk children (regardless of whether they developed dyslexia or not), positive relationships were observed between the right superior longitudinal fasciculus in kindergarten and subsequent non-word reading abilities. This relationship was observed independent of age, nonverbal cognitive abilities, and socioeconomic status, and was not present among typical controls. 

 

Although sentence comprehension and vocabulary knowledge did not differ at the start of formal reading instruction between at-risk children who subsequently developed dyslexia compared to those who did not, significant differences in vocabulary did emerge by the end of second grade….In line with this notion, vocabulary growth has been shown to be a more important predictor of subsequent language and reading development than initial vocabulary size at early stages in development. These findings also support the notion that at-risk children with relative strengths in vocabulary knowledge may be able to discern context clues in text to achieve word identification, despite decoding difficulties. The emerging differences in vocabulary observed over the course of reading acquisition further illuminate the importance of early identification, and suggest that incorporating vocabulary targets in intervention may also be necessary in order to close the gap in exposure that can occur during reading development.

 

Right-hemispheric white matter microstructure at the start of formal reading instruction is linked with subsequent reading outcomes among at-risk children.

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At-risk children without subsequent dyslexia showed significantly higher FA in this tract relative to typical controls as well. A positive relationship between microstructure in the right SLF and subsequent non-word reading (decoding) abilities at the end of second grade was specific to at-risk children only, as there was no relationship observed among typical controls…. The specificity of relationships between the right SLF and subsequent decoding abilities among at-risk children only suggests that at-risk children who acquire better word reading abilities may be utilizing the right-hemispheric correlate of the left-hemispheric ‘indirect route’ for decoding that has been previously characterized in typical reading development. Furthermore, this significant relationship was independent of SES, which suggests that the trajectory of at-risk children in the present study is not solely explainable by socioeconomic factors.

 

 

For at-risk children who do receive targeted instruction or clinical services thereafter, the present findings support the notion that multiple approaches to targeted instruction in the first few years of formal schooling may be particularly effective. In addition to the well-established goal to promote decoding skills, there is potential to reach another level of support through careful consideration of what may be most effective for each child based on a holistic profile of their relative strengths and weaknesses.