Autism may begin during early brain development, when certain neurons in the brain start to form their first connections, a new mice study suggests.
Scientists in Maryland managed to pinpoint where and when autism-related defects in the brain first appear among mice. The results of the study offer hope for early intervention strategies against the disorder.
Early Brain Development
Autism is a neurodevelopmental condition that encompasses a spectrum of complex disorders, each with symptoms of varying degrees.
In the report, researchers from University of Maryland studied the link between autism and the cerebral cortex, the brain region that controls memory, perception, and in humans, abstract reasoning and language.
During development, the cerebral cortex contains a distinct class of cells known as subplate neurons, which form the first circuits or connections of the brain. As the brain matures, these subplate neurons build a network that supports other neurons that grow later.
Researchers Daniel Nagode and Patrick Kanold, together with their colleagues, used a well-established mouse model of autism, which involves injecting valproic acid (VPA) on mouse embryos during day 12 of their 20-day gestational period.
They then used laser scanning photo-stimulation to map the connections between subplate neurons in the brains of mouse pups. A week after being given birth, the mice that received VPA exhibited patterns of hyperconnected subplate neurons and there were too many connections in the brain.
On the other hand, mouse pups that did not receive VPA showed normal connections in their developing cerebral cortex.
After 10 days, researchers found that the hyperconnected subplate neurons among VPA-dosed mouse pups became increasingly widespread and homogenous.
"Subplate neurons form critical developmental structures," said Kanold. "If their early progress is impaired, later development of the cortex is also impaired."
In humans, the development of the cerebral cortex is a critical stage. In fact, subplate neurons are most abundant during this stage, said Kanold.
In mice, the development of subplate neurons takes place after birth. These neurons eventually die off and vanish. However, in humans, these neurons form during the second trimester. When humans are born, most of the subplate neurons then disappear.
Hope For Early Intervention?
Researchers believe the findings of the study suggest that early intervention may be needed to address autism. The fetal brain isn't a small version of the adult brain, with the presence of subplate neurons as the major difference, said Kanold.
"There may ... be other developmental disorders we can tackle using this information," he added.
Details of the study were published in the journal Cell Reports.
