Anatomical and behavioural correlates of auditory perception in developmental dyslexia

Developmental dyslexia is typically associated with difficulties in basic auditory processing and manipulating speech sounds. However, the neuroanatomical correlates of auditory difficulties in developmental dyslexia and their contribution to individual clinical phenotypes are still unknown. Recent intracranial electrocorticography findings associated processing of sound amplitude rises and speech sounds with posterior and middle superior temporal gyrus (STG), respectively. We hypothesize that regional STG anatomy will relate to specific auditory abilities in developmental dyslexia and that auditory processing abilities will relate to behavioral difficulties with speech and reading. One hundred and ten children (78 developmental dyslexia, 32 typically developing, age 7-15 years) completed amplitude rise time and speech-in-noise discrimination tasks. They also underwent a battery of cognitive tests. Anatomical MRI scans were used to identify regions in which local cortical gyrification complexity correlated with auditory behaviour. Behaviourally, amplitude rise time but not speech-in-noise performance was impaired in developmental dyslexia. Neurally, amplitude rise time and speech-in-noise performance correlated with gyrification in posterior and middle STG, respectively. Furthermore, amplitude rise time significantly contributed to reading impairments in developmental dyslexia, while speech in noise only explained variance in phonological awareness. Finally, amplitude rise time and speech-in-noise performance were not correlated, and each task was correlated with distinct neuropsychological measures, emphasizing their unique contributions to developmental dyslexia. Overall, we provide a direct link between the neurodevelopment of the left STG and individual variability in auditory processing abilities in neurotypical and dyslexic populations.