Last Month's Most Accessed Feature: Mapping intelligence: MRI reveals wiring connection

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  • Published: Mar 1, 2018
  • Categories: MRI Spectroscopy
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Signs of intelligence

Jakob Seidlitz is at PhD student on the NIH Oxford-Cambridge Scholars Programme. A graduate of the University of Rochester, USA, he spends half of his time in Cambridge and half at the National Institutes of Health in the USA.

In work funded by the UK's Wellcome Trust and the National Institutes of Health in the USA, researchers at the University of Cambridge have used magnetic resonance imaging to map the connections in the brain and shown that the strength of those connections correlates with a person's intelligence.

Scientists have been attempting to map the connections in the brain to build a picture of the so-called "connectome" for many years. The effort could lead to a deeper understanding of how connections between structures in the brain are reflected in human behaviour and perhaps more importantly how they relate to mental health problems. Now, in research published in the journal Neuron, an international consortium of researchers from the UK (University of Cambridge, University College London, GlaxoSmithKline, and the National Health Service) and the USA (National Institutes of Health), has demonstrated that magnetic resonance imaging (MRI) can be used to construct a representation of the connectome simply by analysing conventional brain scans in a technique known as morphometric similarity mapping.

The team describes their technique as "a robust new method to examine the structural organization of individual brains in vivo." They point out that it provides them with morphometric similarity networks (MSNs) that capture cellular, molecular, and functional features of the brain and predict differences in cognition between individuals.

Scanning for cognitive skills

The researchers examined MRI brain scans of almost 300 typically developing adolescent volunteers. They corroborated the findings with a cohort of an additional 124 volunteers. A conventional 3T MRI scanner was used to acquire the initial scans, but a 7T machine at Cambridge allowed them to obtain even more precise mapping information about the human brain.

The researchers explain that a standard MRI scan will provide a single image of the brain from which can be determined multiple structural features of the brain. Each region of the brain can then be described using up to ten different characteristics. The team found that if two regions have similar profiles, then they can be described as having "morphometric similarity". The existence of such similarities implies that these two regions are part of a connected network. The team had verified this assumption using publically available MRI data on a cohort of 31 juvenile rhesus macaque monkeys to compare to "gold-standard" connectivity estimates in that species.

Next, the researchers were able to use these morphometric similarity networks (MSNs), to construct a map showing how well connected are the major connection points between different regions of the brain network, the network hubs. The team found a link between the connectivity in the MSNs in brain regions linked to higher order functions, which includes problem solving, language, and intelligence.

Mental health scan

"We saw a clear link between the 'hubbiness' of higher-order brain regions – in other words, how densely connected they were to the rest of the network – and an individual's IQ," explains Jakob Seidlitz who splits his time between Cambridge and Bethesda. "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," he adds.

While IQ (intelligence quotient) is only a proxy for actual intelligence it is a useful tool for estimating cognition broadly. IQ varied across all participants and the team suggests that the MSNs accounted for about 40 percent of the variation. It is possible, the researchers suggest, that higher-resolution multi-modal data provided using the 7T scanner might be able to account for an even greater proportion of the individual variation.

"What this doesn’t tell us, though, is where exactly this variation comes from," Seidlitz concedes. "What makes some brains more connected than others – is it down to their genetics or their education and upbringing, for example? And how do these connections strengthen or weaken across development?"

The work might take us a step closer to being able to estimate intelligence from a brain scan, rather than having to rely on an IQ test, which is not always the most appropriate measure for different people. Ed Bullmore, Head of Psychiatry at the University of Cambridge adds that, "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."

Related Links

Neuron 2017, 97, 231-237: "Morphometric Similarity Networks Detect Microscale Cortical Organization and Predict Inter-Individual Cognitive Variatio"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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