A new study associates autism with weak connections between the brain’s thalamus and its cerebral cortex. The thalamus is the deep-seated part of the brain that relays incoming sensory information. The brain’s outer cerebral cortex coordinates responses to this input.
Because the thalamus is a kind of central “relay station” for incoming information, the compromised connections may help explain the wide range of impairments that affect many individuals with autism. These include not only social and language disabilities, but also sensory and movement issues.
“Insights into the brain biology behind disabling autism symptoms are crucial for advancing the current state of diagnostics and treatment of autism,” comments Daniel Smith, Ph.D., Autism Speaks senior director of discovery neuroscience. “This research exemplifies the kind of work we need in our quest to understand the core social impairments and underappreciated sensory processing differences in autism.”
The study appears in this month’s issue of the journal BRAIN. Its lead author, Aarti Nair, is pursuing her research as part of an Autism Speaks Dennis Weatherstone Predoctoral Fellowship. She is doing so under the mentorship of Ralph-Axel Müller, Ph.D., in San Diego State University’s Brain Development Imaging Laboratory.
Their study is the first to combine magnetic resonance imaging and diffusion tensor imaging to examine connections between the cerebral cortex and the thalamus in individuals with autism. The team used these noninvasive techniques to study brain activity and anatomy in 53 children. Twenty-nine had autism. Thirty-four did not.
“In the children with autism, we found that the pathways connecting the cerebral cortex and thalamus were compromised, indicating that these two parts of the brain don't communicate well with each other,” Nair says.
“This impaired connectivity suggests that autism is not simply a disorder of social and communicative abilities, but also affects a broad range of sensory and motor systems,” Dr. Müller adds. “Disturbances in the development of the thalamus could play a key role in autism symptoms.”
The findings also support the argument that the diagnosis of autism should include a broader spectrum of problems than just social and language difficulties, the researchers conclude.
Launching careers in autism research
Autism Speaks Weatherstone Predoctoral Fellowships are designed to advance high-priority areas of autism research while launching promising scientists into productive careers in the field.
Nair’s Weatherstone project seeks to advance understanding of the brain networks that connect with the thalamus. Prior brain-imaging studies have identified highly specific connection patterns between the thalamus and the cerebral cortex in the “typically developed” brain. However, little imaging research had been done on connections between the thalamus and cortex in persons with autism. As such, Nair’s work is opening a new area of research.
“Now in its fifth year, the Weatherstone predoctoral fellowship program resulted from a generous gift from the Stavros Niarchos Foundation,” says Anita Miller Sostek, Autism Speaks vice president for scientific review. “Ms. Nair’s impressive research adds to the remarkable productivity of these promising fellows, who have chosen to devote their careers to autism research.”