Anatomical and behavioral correlates of auditory perception in developmental dyslexia

Abstract

AbstractDevelopmental dyslexia (DD) is typically associated with difficulties in manipulating speech sounds and, sometimes, in basic auditory processing. However, the neuroanatomical correlates of auditory difficulties in DD and their contribution to individual clinical phenotypes are still unknown. Recent intracranial electrocorticography (ECoG) 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 DD and that auditory processing abilities will relate to behavioral difficulties. One hundred and ten children (78 DD, 32 typically developing, age 7-15 years) completed amplitude rise time (ART) and speech in noise discrimination (SiN) 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 tasks in DD. Behaviorally, ART but not SiN performance was impaired in DD. Neurally, ART and SiN performance correlated with gyrification in posterior STG and middle STG, respectively. Furthermore, ART significantly contributed to reading impairments in DD, while SiN explained variance in phonological awareness only. Finally, ART and SiN performance was not correlated, and each task was correlated with distinct neuropsychological measures, such that distinct DD subgroups could be identified. Overall, we provide a direct link between the neurodevelopment of the left STG and individual variability in auditory processing abilities in DD. The dissociation between speech and non-speech deficits supports distinct DD phenotypes and implicates different approaches to interventions.Significance statementThe capacity to read is crucial for human development yet challenging for individuals with developmental dyslexia (DD). Individuals with DD show a range of auditory and speech processing deficits. We tested non-speech and speech processing abilities in DD and typically developing children, and combined them with measures of neuroanatomical structure in the human auditory speech cortex on the superior temporal gyrus (STG).This unique combination revealed a behavioral and neuroanatomical dissociation between the speech and non-speech processing. Each task was uniquely related to a subdivision of the STG, and a distinct set of cognitive abilities. Our findings contribute to the understanding of auditory processing deficits in dyslexia and have clinical implications for individual phenotypes of individuals with DD.