Mastering subtle actions—wielding a fork or turning the pages of a book, for example—occur at different ages for girls and boys, and children with autism tend to lag behind those without the condition.
Those differences may relate to changes in the striatum during development, according to a new study. Improved fine motor skills are linked to maturation of distinct striatal pathways in autistic boys and girls, MRI scans of toddlers revealed.
The findings “put to bed any doubt” about the striatum’s contribution to subtle movements, says Ann Graybiel, professor of brain and cognitive sciences at the Massachusetts Institute of Technology, who was not involved in the research. And further analysis of the data might uncover associations between other autism traits and sex-specific brain changes, Graybiel says.
The striatum—a cluster of cells that link motivation to movement—has been tied to restricted interests and repetitive behaviors and shows sex-specific differences in autistic adolescents, previous studies have shown. But the tendency of toddlers to wriggle around in an MRI scanner has hampered similar research in children younger than 5—a critical period of neurodevelopment.
That lack of data on younger children and girls has made it tricky for researchers to probe how sex influences brain development in children with autism, says Emma Duerden, associate professor of applied psychology at the University of Western Ontario in London, Canada, who was not involved in the work. “We really don’t know much about the development of the brain in very young children with autism. [Yet] it’s a really sensitive window,” Duerden says.
By recruiting 2- and 3-year-old girls to the Autism Phenome Project—followed by some late nights in the imaging center—the researchers behind the new work gathered MRI scans from 356 sleeping toddlers, including 234 with autism. The team then scored the group—a third of whom were girls—on their fine motor skills based on the researchers’ observations and reports from caregivers, who also provided their children’s sex assigned at birth.
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mong toddlers without autism, fine motor skills are more advanced in girls than in boys, the study found, chiming with previous research that girls develop these abilities at an earlier age. Autistic toddlers score lower than non-autistic ones and show volume differences in a part of the striatum called the putamen, the researchers also found.But those changes vary by sex: Better fine motor skills track with a smaller putamen volume among autistic girls but a larger putamen volume among their male counterparts.
The team then analyzed two key striatal pathways: one that connects the cell cluster with cognitive regions and another that links it to parts of the brain that receive sensorimotor signals. Better fine motor skills correlate with higher integrity of white-matter tracts in the sensory pathway among autistic boys but not autistic girls, the study found.
In a follow-up assessment of 195 of the original participants, including 113 autistic children, alterations in both the sensorimotor and cognitive pathways at age 3 predicted rates of fine motor skill development over the next two years in autistic girls but not in autistic boys, the researchers found. The results were published 14 January in Biological Psychiatry.
The findings suggest that autistic boys and girls likely rely on these pathways to different extents during development, says study investigator Olivia Surgent, a postdoctoral fellow at the University of California, Davis MIND Institute.
Follow-up assessments in mid-childhood and teenage years in the project’s next stages should reveal whether the different sexes lean on distinct pathways throughout childhood, or if those differences disappear with age, says Christine Wu Nordahl, the study’s principal investigator and professor of psychiatry and behavioral sciences at the University of California, Davis MIND Institute.
Either way, charting autistic children’s developmental trajectories should reveal when they are best primed to undergo training in fine motor skills, Nordahl says.
