How does learning to read shape the neural representation of spoken and written language?

Writing systems vary in the way they express the sounds and meanings of spoken language. Alphabetic writing systems contain information about phonological structure within the orthography due to systematic relations between graphemes and phonemes. Logographic writing systems encode less-fine-grained information about phonological structure via more arbitrary mappings between characters and syllables. We tested whether differences in orthographic structure impact on reading acquisition and the spoken language representations that underpin reading (e.g., Rastle et al., 2011). Twenty-four adult participants were trained on two artificial languages with alphabetic and logographic writing systems. Each language contained 24 words denoted by phonological, orthographic, and semantic components. Learning involved completing computerised tasks over 10 days before performance was assessed using behavioural tests. Following training, neural activity was recorded using fMRI whilst participants made meaning judgements about trained spoken and written stimuli.

We assessed the development of mappings between sounds, spellings, and meanings of words and the division of labour between dorsal and ventral reading pathways. Performance was compared using linear mixed-effect models and neural activity was contrasted using paired-samples t-tests. Representational similarity analysis assessed whether alphabetic and logographic systems influence neural sensitivity to phonemic, orthographic, and semantic structure during reading and listening. Overall, alphabetic words exhibited stronger orthography–phonology mappings while orthography– semantic mappings were stronger for logographic words. The dorsal pathway showed greater activity for alphabetic written words; the ventral pathway was more active for logographic written words. Representations only encoded the phonemic/orthographic structure of alphabetic written and spoken words. No orthographic effects on spoken language were observed. These findings advance our understanding of how writing systems impact on reading acquisition and spoken language. They suggest different strategies are used to learn alphabetic and logographic languages and that orthographic transparency can impact on the division of labour and underlying representations.