Toward a Mechanistic Understanding of Reading Difficulties: Deviant Audiovisual Learning Dynamics and Network...

Mastering the associations between letters and their corresponding speech sounds (LSS) is pivotal in the early stages of reading development, requiring an effective reorganization of brain networks. Children with poor reading skills often show difficulties in LSS learning. To date, however, it remains unclear how the interaction of brain regions integral to the processing and integration of letters and speech sounds changes with LSS learning. Characterizing these changes and potential differences between children with typical (TR) or poor (PR) reading skills on both behavioral and neural levels is essential for a more comprehensive mechanistic understanding of reading impairments. In this study, we investigated brain network alterations underlying LSS learning and their association with reading skills using functional magnetic resonance imaging in 80 schoolchildren (6.9-10.8 years, 36 females, 27 PR) with a wide range of reading skills. We applied a reinforcement learning drift-diffusion model to LSS learning data and analyzed the corresponding effective connectivity and activation measures in the brain. While both groups learned well, PR showed slower adaptation of responses than TR as trials progressed. This could be explained by a slower adjustment of the drift rate and decision boundary while learning and longer nondecision times. Alongside deviant connectivity in the network of visual, auditory, and associative brain regions, PR also showed reduced striatal modulation of connectivity from visual to audiovisual association areas throughout learning. These findings indicate impaired information transfer to integrative areas, which aids to explain the difficulties in achieving proficient reading skills from a neuroscientific perspective.