Researchers discover how autism affects the ‘social brain’

A research team from UCLA has discovered that brain areas linked to social behaviors in those with autism spectrum disorder (ASD) are underdeveloped and have substantially fewer network connectivity than in study participants without ASD. The study, which is published in Brain and Behavior, helps to advance understanding of the nature of ASD by pairing the disorder with concrete aspects of the brain.

“The brain controls most of our behavior and changes in how brain areas work and communicate with each other can alter this behavior and lead to impairments associated with mental disorders,” said study author Kay Jann, a postdoctoral researcher in the UCLA Department of Neurology, in a statement.

“When you match physiologic changes in the brain with behavioral impairment, you can start to understand the biological mechanisms of this disorder, which may help improve diagnosis, and, in time, treatment.”

In particular, the researchers were interested in examining the structure and function of neural networks associated with the “social brain”.

Studying the default mode

To study this, the group used an MRI tool known as arterial spin labelling perfusion, which uses magnetically-labelled blood water to trace blood flow—the first time this tool has been used to study ASD.

For the brain in particular, blood flow is a common technique for research. More blood flow to a region indicates that region is using more energy, and that it requires more oxygen than other regions. This in turn signifies that a particular region is active. But the team also used different technology to measure how interconnected various regions of the brains were, as both blood flow and neural networks have been of major interests for those studying neurological disorders.

“In neurocognitive or neuropsychiatric disorders, these two crucial properties — functional organization of the brain and its accompanying energy demands — are often found to be altered,” explained study senior author Danny J.J. Wang, an associate professor of neurology at UCLA.

Focusing on these two key components, the researchers studied something known as the default mode network in 22 typically developing children and adolescents, as well as 17 youths with high-functioning ASD. These two groups were matched by age, sex, and IQ scores.

“[T]he default mode network has become a focus of such research, because it is important for social and emotional processes, self-referential thought, and in ‘Theory of Mind,’ which is the ability to attribute mental states to one-self and to others,” Wang explained. “These are cognitive processes that are to some extent impaired in persons with autism spectrum disorders.”

Blood flow shows delayed social regions

The tests revealed significant differences between the two groups. The youths with ASD displayed hyper-perfusion—widespread increased blood flow. This blood flow was linked with increased oxygen metabolism in the frontal bran areas, which are responsible for social interactions.

Such blood flow is generally reduced as the brain develops—as exemplified in the typically developing children—so this continued hyper-perfusion in participants with ASD suggests that these frontal “social” regions may have had delayed development.

Moreover, the team found that the children with ASD had reduced long-range connectivity between certain default network nodes (conjunction points in the network). The nodes were located in the front and back of their brains, meaning information cannot flow as freely between distant areas of the brain, and this may explain the typical impairment in social responsiveness.

“The architecture of the brain follows a cost efficient wiring pattern that maximizes functionality with minimal energy consumption,” Jann said. “This is not what we found in our ASD participants.”

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