Longitudinal processing speed impairments in males with autism and the effects of white matter microstructure

Abstract

The present study used an accelerated longitudinal design to examine group differences and age-related changes in processing speed in 81 individuals with Autism Spectrum Disorder (ASD) compared to 56 age-matched individuals with typical development (ages 6–39 years). Processing speed was assessed using the Wechsler Intelligence Scale for Children-3rd edition (WISC-III) and the Wechsler Adult Intelligence Scale-3rd edition (WAIS-III). Follow-up analyses examined processing speed subtest performance and relations between processing speed and white matter microstructure (as measured with diffusion tensor imaging [DTI] in a subset of these participants). After controlling for full scale IQ, the present results show that processing speed index standard scores were on average 12 points lower in the group with ASD compared to the group with typical development. There were, however, no significant group differences in standard score age-related changes within this age range. For subtest raw scores, the group with ASD demonstrated robustly slower processing speeds in the adult versions of the IQ test (i.e., WAIS-III) but not in the child versions (WISC-III), even though age-related changes were similar in both the ASD and typically developing groups. This pattern of results may reflect difficulties that become increasingly evident in ASD on more complex measures of processing speed. Finally, DTI measures of whole-brain white matter microstructure suggested that fractional anisotropy (but not mean diffusivity, radial diffusivity, or axial diffusivity) made significant but small-sized contributions to processing speed standard scores across our entire sample. Taken together, the present findings suggest that robust decreases in processing speed may be present in ASD, more pronounced in adulthood, and partially attributable to white matter microstructural integrity.

Multivariate characterization of white matter heterogeneity in autism spectrum disorder

“…Participants consisted of 92 individuals with ASD and 57 typically developing controls (TDC), selected from a broader longitudinal study of brain development in autism and typical development (Lange et al, 2015, Travers et al, 2015b, Travers et al, 2015a, Travers et al, 2014, Zielinski et al, 2014). Consent was obtained from all adult participants, and both parental consent and participant assent were obtained for participants under the age of 18 years.…”

Magnetoencephalographic Imaging of Auditory and Somatosensory Cortical Responses in Children with Autism and Sensory Processing Dysfunction

“…For example, there is some evidence of reduced processing speed in ASD (Hedvall et al, 2013; Travers et al, 2014), which has been associated with white matter structural integrity (Lazar et al, 2014; Travers et al, 2014), frontal lobe volume (Schmitz et al, 2007), communication (Oliveras-Rentas et al, 2012), and adaptive functioning (Hedvall et al, 2013). Other studies, however, have failed to identify significant differences in processing speed for participants with ASD relative to typically developing peers (Scheuffgen et al, 2000; Wallace et al, 2009), particularly when motor demands are minimized (Kenworthy et al, 2013).…”

Relationship between brain stem volume and aggression in children diagnosed with autism spectrum disorder

“…TD participants were evaluated using ADOS, IQ, language tests, and parent interview to confirm that all had age appropriate verbal skills and no history of learning, developmental, cognitive, neurological, or neuropsychiatric problems (Alexander, et al, 2007; Allen-Brady, et al, 2010; Jantz, et al, 2015; Prigge, et al, 2013; Travers, et al, 2014). See Table 1 for more detailed descriptions of participant recruitment and characteristics.…”