Longitudinal processing speed impairments in males with autism and the effects of white matter microstructure.
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.
['Travers|Brittany G|BG|', 'Bigler|Erin D|ED|', 'Tromp|Do P M|do PM|', 'Adluru|Nagesh|N|', 'Froehlich|Alyson L|AL|', 'Ennis|Chad|C|', 'Lange|Nicholas|N|', 'Nielsen|Jared A|JA|', 'Prigge|Molly B D|MB|', 'Alexander|Andrew L|AL|', 'Lainhart|Janet E|JE|']
D000293:Adolescent D000328:Adult D016880:Anisotropy D001321:Autistic Disorder D001921:Brain D002648:Child D002657:Child Development D056324:Diffusion Tensor Imaging D006801:Humans D007361:Intelligence Tests D016014:Linear Models D008137:Longitudinal Studies D008297:Male D009413:Nerve Fibers, Myelinated D013850:Thinking D013997:Time Factors D055815:Young Adult
Processing speed Autism White matter Diffusion tensor imaging Executive function