A simple technique for mapping the wiring of the brain — called morphometric similarity mapping — has shown a correlation between how well connected an individual’s brain regions are and their IQ. The results appear in the journal Neuron.
According to Seidlitz et al, morphometric similarity mapping provides a novel, robust, and biologically plausible approach to understanding how human brain networks underpin individual differences in psychological functions. Image credit: Gordon Johnson.
In recent years, there has been a concerted effort among scientists to map the connections in the brain — the so-called connectome — and to understand how this relates to human intelligence and mental health disorders.
Now, Jakob Seidlitz from the University of Cambridge, UK, and the National Institutes of Health, the United States, and co-authors have shown that it is possible to build up a map of the connectome by analyzing conventional brain scans taken using a magnetic resonance imaging (MRI) scanner.
“We saw a clear link between the ‘hubbiness’ of higher-order brain regions and an individual’s IQ,” Seidlitz said.
“This makes sense if you think of the hubs as enabling the flow of information around the brain — the stronger the connections, the better the brain is at processing information.”
In the study, the researchers compared the brains of 296 typically-developing adolescent volunteers.
Their results were then validated in a cohort of a further 124 volunteers.
They showed that if two regions have similar profiles, then they are described as having ‘morphometric similarity’ and it can be assumed that they are a connected network.
They verified this assumption using MRI data on a cohort of 31 juvenile rhesus macaque monkeys to compare to ‘gold-standard’ connectivity estimates in that species.
Using these morphometric similarity networks (MSNs), the team was able to build up a map showing how well connected the ‘hubs’ were.
The authors found a link between the connectivity in the MSNs in brain regions linked to higher order functions — such as problem solving and language — and intelligence.
“While IQ varied across the participants, the MSNs accounted for around 40% of this variation — it is possible that higher-resolution multi-modal data provided by a scanner may be able to account for an even greater proportion of the individual variation,” Seidlitz and colleagues said.
“What this doesn’t tell us, though, is where exactly this variation comes from.”
“What makes some brains more connected than others — is it down to their genetics or their educational upbringing, for example? And how do these connections strengthen or weaken across development?”
“This could take us closer to being able to get an idea of intelligence from brain scans, rather than having to rely on IQ tests,” said study senior author Professor Ed Bullmore, from the University of Cambridge.
“Our new mapping technique could also help us understand how the symptoms of mental health disorders such as anxiety and depression or even schizophrenia arise from differences in connectivity within the brain.”
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Jakob Seidlitz et al. 2018. Morphometric Similarity Networks Detect Microscale Cortical Organization and Predict Inter-Individual Cognitive Variation. Neuron 97 (1): 231-247; doi: 10.1016/j.neuron.2017.11.039
