The relation of home literacy environment to brain specialization for phonological and semantic processing in 5- to 6-year-old children

Phonological and semantic processing are two critical components of language comprehension and serve as foundations for reading acquisition (Frost et al., 2005; Wang et al., 2020). According to the Interactive Specialization account (Johnson, 2011), brain cortices start with broad functionality and then become selective to narrower functions as children develop, which is a process that is referred to as functional specialization. Developmental disorders are often associated with atypical or delayed specialization. Thus, understanding how and why children develop their brain specialization is the key to helping children with developmental disorders. For phonological and semantic processing in the brain, a prior study using two auditory word processing tasks – a sound judgment task and a meaning judgment task – demonstrated that 5- to 6-year-old children exhibited phonological and semantic specialization in temporal brain regions (Weiss et al., 2018). Specifically, greater activation for the sound than the meaning judgment task was found in the left superior temporal gyrus (STG). In addition, greater activation for the meaning than the sound judgment task was observed in the left posterior middle temporal gyrus (pMTG). However, what contributes to the development of language specialization remains to be examined. A stimulating learning environment is a critical factor supporting the development of a child's cognitive abilities and educational outcomes. In the early years language input is aural, later supplemented by written forms when literacy instruction begins at school (Hulme et al., 2020). Mounting evidence indicates that the home literacy environment (HLE), including parental literacy, access to books, interactions with adults in reading activities, or exploration of print by children on their own, is one of the predictors of early language and reading skill development (Mol & Bus, 2011; Sénéchal & LeFevre, 2014; Wirth et al., 2020). In behavioral studies, HLE was found to be associated with phonological awareness (Niklas & Schneider, 2013) and vocabulary skills (Frijters et al., 2000; Sénéchal & LeFevre, 2014). Moreover, research using functional magnetic resonance imaging (fMRI) suggested a close relation between HLE and functional activity within language-related brain regions (see Hutton et al., 2021 for review). For example, Hutton et al. (2015) found that 3- to 5-year-old children with greater home reading exposure exhibited more robust activation within a semantic comprehension network, including the middle temporal gyrus, while listening to stories. Thus, HLE has been found to be associated with language networks during various language or reading tasks. However, whether HLE supports phonological and semantic brain specialization remains unknown. Recently we have pre-registered a study that aimed to investigate the relation between HLE and brain specialization for phonological and semantic auditory language processing in the group of 7- to 8-year-olds (https://osf.io/xrgtu). The goal of the current study is to investigate the relation between a child's environment and brain specialization in the younger cohort of 5- to 6-year-old children. Two aspects of HLE will be selected: 1) amount of time a child is read to by a family member each day and 2) amount of time a child reads to themself or others each day. For the list of references see Preregistration_5-6.y.o_References.pdf in https://osf.io/rpyfg/