Right-hemispheric white matter organization is associated with speech timing in autistic children

Converging research evidence indicates that speech timing, including altered rate and pausing when speaking, is an important characteristic distinguishing autistic individuals from non-autistic peers. Although speech timing can impact effective social communication, it remains unclear what mechanisms underlie individual differences in speech timing in autism. Therefore, the present study examined the organization of key speech- and language-related neural pathways in relation to speech timing in autistic and non-autistic children. Secondary analysis of a multimodal dataset included 24 autistic children and 24 non-autistic children (ages: 5 – 17 years). Audio recordings from a naturalistic language sampling task (via narrative generation) were transcribed to extract speech timing features (i.e., speech rate, pause duration). White matter organization (as indicated by fractional anisotropy (FA)) was estimated for key tracts bilaterally (i.e., arcuate fasciculus (AF), superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF), and frontal aslant tract (FAT)). Results indicate associations between speech timing and right-hemispheric white matter organization (i.e., FA in right ILF and FAT) were specific to autistic children and not observed among non-autistic controls. Among non-autistic children, associations with speech timing were specific to the left hemisphere (i.e., FA in the left SLF). All effects are significant controlling for age, sex, and nonverbal IQ. Overall, these findings enhance understanding of the neural architecture influencing speech timing in autistic and non-autistic children and, thus, carry implications for understanding potential neural mechanisms underlying speech timing differences in autism.