Towards a mechanistic understanding of reading difficulties: Deviant audiovisual learning dynamics and network connectivity in children with poor reading skills

Mastering the associations between letters and their corresponding speech sounds (LSS) is pivotal in the early stages of reading development, requiring an effective reorganisation 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. Characterising these changes and potential differences between children with typical (TR) or poor (PR) reading skills on both behavioural 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-old, 36 female, 27 PR) with a wide range of reading skills. We applied a reinforcement-learning drift-diffusion model to LSS learning data and analysed 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 non-decision 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 audio-visual association areas throughout learning. These findings indicate impaired information transfer to integrative areas, which can help to explain the difficulties in achieving proficient reading skills from a neuroscientific perspective.Significance statement This study investigated how children's brains learn to connect letters with speech sounds, a key step in reading development. Using brain imaging and computational models, we found that children with poor reading skills showed a less efficient adaptation of their decision-making strategy while learning letter-speech sound correspondences. The brain network connecting visual, auditory, and association areas in these children showed weaker connectivity and the modulation of connectivity by a key learning-related striatal region was diminished. These findings help explain the challenges faced by children with reading difficulties and provide new insights into the brain mechanisms behind reading problems.