Why Having Well-Connected Brain Hubs Matters

Developmental disorders in childhood may be tied to poorly-connected brain hubs.

Posted Mar 01, 2020

Roma Siugzdaite
Brain map showing examples of networks and hubs.
Source: Roma Siugzdaite

Poorly-connected brain hubs and childhood developmental disorders often go hand in hand, according to a new state-of-the-art brain mapping study from the University of Cambridge. The findings (Siugzdaite et al., 2020) were published on February 27 in the journal Current Biology.

"The purpose of this study was to take a transdiagnostic approach to establish how brain differences relate to cognitive difficulties in childhood," the authors said.

Notably, the researchers found that measuring patterns of white-matter connectivity between brain hubs appears to be a more effective way to predict cognitive difficulties and developmental disorders than focusing solely on the amount of gray matter in specific brain regions.

In a press release, the authors used a train station analogy to convey the importance of having well-connected brain hubs. "Children with poorly connected hubs—like a train station with few or poor connections—had widespread and severe cognitive problems," they said.

Until recently, most neuroscientists presumed that developmental disorders and learning difficulties corresponded directly to specific brain regions. However, the findings of this brain mapping study suggest that gray matter differences in specific brain regions are not an effective way to predict things like autism spectrum disorder (ASD) or attention-deficit/hyperactivity disorder (ADHD).

Interestingly, the Cambridge Neuroscience researchers found that, in general, differences between specific brain regions didn’t match the diagnostic label that a child had been given. As the authors explain, "There were no brain regions that predicted having ASD or ADHD.”

For decades, neuroscientists have struggled to isolate precisely which brain areas are associated with specific developmental disorders. Unfortunately, parents are often given a laundry list of brain regions that may be related to their child's developmental disorder. "Take ADHD," the authors write. "This disorder has been associated with differences in gray matter within the anterior cingulate cortex, caudate nucleus, pallidum, striatum, cerebellum, prefrontal cortex, the premotor cortex, and most parts of the parietal lobe."

"Scientists have argued for decades that there are specific brain regions that predict having a particular learning disorder or difficulty, but we've shown that this isn't the case," senior author Duncan Astle of Cambridge Neuroscience said in a news release. "In fact, it's much more important to consider how these brain areas are connected—specifically, whether they are connected via hubs. The severity of learning difficulties was strongly associated with the connectedness of these hubs, we think because these hubs play a key role in sharing information between brain areas."

These recent (2020) findings may explain why certain drugs such as methylphenidate (Ritalin), which is used to treat ADHD, may effectively reduce hyperactivity but not necessarily improve cognitive outcomes. According to the authors, these stimulant medications target specific types of nerve cells but have little or no impact on the 'hub-based' organization of whole-brain networks.

This brain mapping research also suggests that sticking to rigid diagnostic labels (e.g., ADHD, ASD) can backfire if the diagnosis is based on faulty presumptions about the role that specific brain regions play in any given developmental disorder.

"Receiving a diagnosis is important for families. It can give professional recognition for a child's difficulties and open the door to specialist support. But in terms of specific interventions, for example from the child's teachers, [diagnostic labels] can be a distraction,” Astle said.

"It's better to look at their areas of cognitive difficulties and how these can be supported," he added. "For example, using specific interventions to improve listening skills or language competencies, or at interventions that would be good for the whole class, like how to reduce working memory demands during learning."

Although this is the first time scientists have used transdiagnostic brain mapping to investigate how the connectedness of neural hubs predicts cognitive differences in childhood, other recent studies have also put the importance of well-connected brain hubs in the spotlight. See "Move Over, Gray Matter—White Matter Is Taking Center Stage" and "Highly Creative People Have Well-Connected Brain Hemispheres."

References

Roma Siugzdaite, Joe Bathelt, Joni Holmes, Duncan E. Astle. "Transdiagnostic Brain Mapping in Developmental Disorders." Current Biology (First published: February 27, 2020) DOI: 10.1016/j.cub.2020.01.078