Autism linked to overconnectivity in brain networks

Adolescents with ASDs show atypically increased functional connectivity between two brain networks that are crucial for social cognition.

Autism linked to overconnectivity in brain networks
Autism linked to overconnectivity in brain networks

HealthDay News -- Adolescents with autism spectrum disorder (ASD) show atypically increased functional connectivity involving two brain networks that are crucial for social cognition, according to researchers.

Ralph-Axel Müller, PhD, of San Diego State University in California and colleagues analyzed connectivity between the theory of mind (ToM) network and the mirror neuron system (MNS) in 25 adolescents with ASD aged 11 to 18 years and 25 typically developing adolescents. Participants were matched for age, handedness and nonverbal IQ. The findings were published online in JAMA Psychiatry.

The ToM network is the region of the brain that controls our ability to understand and interpret someone else's perspective, Muller explained, whereas the MNS allows us to understand and interpret the actions of others and compare them to actions we ourselves perform.

"One crucial problem in autism research is that this disorder, which is generally considered a neurological disorder, is still diagnosed based on purely behavioral criteria. This hasn't changed with the DSM-5 that came out last year. The field lacks reliable biomarkers. The imaging research that our group is doing pursues the target of identifying  biomarkers," Müller said.

The researchers found that participants with ASD showed a mixed pattern of both over- and underconnectivity in the ToM network, which is associated with greater social impairment compared with controls.

This increased connectivity was seen primarily between the regions of the MNS and ToM. The connectivity increase was correlated with sociocommunicative measures, suggesting that excessive ToM-MNS "cross talk" might be associated with social impairment.

A subset of the 15 participants with ASD with the most severe symptomology showed exclusive overconnectivity effects in both ToM and MNS networks, which were also associated with greater social dysfunction compared with a tightly matched subset of 15 typically developing controls.

Previous research has supported a theory that regions of the brain are underconnected in children with ASDs, but it seems that there is another aspect of the disorder is more complex, according to the researchers.

"We can conclude from this current study that connectivity within specialized functional networks like the MNS and ToM network, within those networks is actually slightly or sometimes robustly reduced in autism. However, these networks tend to talk or be connected to too many other parts of the brain, so there is what we could consider noisy information transfer," Müller said.

The study findings put researchers one step closer to identifying biomarker-based subtypes of autism that could help better explain the interactions between genetic and environmental risk factors in children with ASDs.

"Once we know subtypes, we are a step closer to true mechanistic models of the developmental disturbances that occur in autism [...] which are ultimately the prerequisite for a fully targeted treatment," Müller said.

References

  1. Fishman I et al. JAMA Psychiatry. 2014; doi:10.1001/jamapsychiatry.2014.83.
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