Multisensory integration while learning to read: A longitudinal functional and structural MRI study

Literacy development involves the recognition and integration of auditory and visual signals and as such offers a unique opportunity to track the development of an eventually efficient multisensory processing network. To shed light on this topic we conducted a 12-month longitudinal 3 Tesla functional and structural MRI study in children beginning to receive formal literacy instruction. Twenty-three six-year-old German-speaking participants completed four fMRI sessions during which they were presented with letters, speech sounds, or their audiovisual combinations in congruent and incongruent formats. Longitudinal changes in BOLD response amplitude were assessed using linear mixed-effects models. Over the course of learning to read, we observed significant changes in modulations of BOLD activity for the congruent - incongruent contrast within a left-lateralised network encompassing the central opercular cortex, anterior supramarginal gyrus, inferior frontal gyrus (pars triangularis) and frontal pole. These effects were primarily driven by a gradual increase of response amplitude across sessions, consistent with the refinement of audiovisual integration mechanisms. Together, these findings demonstrate reorganisation within established regions known to be related to language processing and multisensory integration during early literacy development, highlighting the utility of longitudinal MRI for tracking experience-dependent neuroplastic changes in brain function and structure.