Lexical morphology as a source of risk and resilience for learning to read with dyslexia: An fNIRS investigation

Purpose: To understand the role of meaning-based skills in learning to read with dyslexia, we examined the neuro-cognitive bases of lexical morphology in children of varied reading abilities.Method: Children completed auditory morphological and phonological awareness tasks during functional near-infrared spectroscopy neuroimaging. We first examined the relation between lexical morphology and phonological processes in typically developing readers (Study 1, N = 66, Mage = 8.39), followed by a more focal inquiry into lexical morphology processes in dyslexia (Study 2, N = 50, Mage = 8.62). We then conducted a data-driven network analysis to examine functional connectivity during lexical morphology processes in all participants (Study 3, N = 91, Mage = 8.77).Results: Typical readers exhibited stronger engagement of language neurocircuitry during the morphology task relative to the phonology task, suggesting that morphological analyses involve a synthesis of multiple components of sublexical processing. This effect was stronger for more analytically complex derivational morphemes (like+ly) relative to more semantically transparent free root morphemes (snow+man). In contrast, children with dyslexia exhibited stronger activation during the free root relative to derivational morpheme conditions, possibly because children with dyslexia use semantic information to boost word recognition. Data-driven and person-specific functional connectivity analyses revealed two groups of readers with either denser fronto-temporal or temporal-only connections. Stronger readers with and without dyslexia were more likely to fall into the fronto-temporal group.Conclusions: This study informs literacy theories by identifying an interaction between reading ability, word structure, and the way that the developing brain learns to recognize words in speech and in print.