Letter-speech sound integration in typical reading development during the first years of formal education.

This study investigated the neural basis of letter and speech sound (LS) integration in 53 typical readers (35 girls, all White) during the first 2 years of reading education (ages 7-9). Changes in both sensory (multisensory vs unisensory) and linguistic (congruent vs incongruent) aspects of LS integration were examined. The left superior temporal cortex and bilateral inferior frontal cortex showed increasing activation for multisensory over unisensory LS over time, driven by reduced activation to speech sounds. No changes were noted in the congruency effect. However, at age nine, heightened activation to incongruent over congruent LS pairs were observed, correlating with individual differences in reading development. This suggests that the incongruency effect evolves at varying rates depending on reading skills.