New brain mapping technique reveals link between connectivity and IQ

According to a team of researchers at the University of Cambridge and the National Institutes of Health (NIH), USA, a novel and comparatively simple technique that maps the wiring of the brain has indicated a relationship between how well connected a person’s brain regions are and their intelligence.

Credit: MriMan/ Shutterstock.com

The study, which was published in the journal Neuron, suggests that it is possible to build up a map of the connectome---the connections in the brain---by examining conventional brain scans obtained using a magnetic resonance imaging (MRI) scanner.

Scientists, for the past few years, have been making a concerted effort to map the connectome and to understand its association with human behaviors like intelligence and mental health disorders.

The current study used a conventional 3T MRI scanner---where 3T stands for the strength of the magnetic field---to compare the brains of 296 typically developing adolescent participants. The findings were then validated via a cohort study of another 124 participants.

A conventional MRI scan provides a single image of the brain that enables the calculation of multiple structural features of the brain; i. e., each region of the brain can be described using nearly ten distinct characteristics.

If two regions of the brain have similar profiles, the researchers described them as having “morphometric similarity,” and are assumed to be a connected network.

This assumption was verified using publically available MRI data on a cohort of 31 juvenile rhesus macaque monkeys, in order to compare to “gold-standard” connectivity estimates in that species.

The team built up a map indicating how well connected the major connection points, called “hubs,” between different regions of the brain network were, by utilizing the morphometric similarity networks (MSNs).

The findings suggested an association between the connectivity in the MSNs in brain regions related with higher order functions, like problem solving and language, and intelligence.

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. 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."

Jakob Seidlitz, University of Cambridge and NIH

While the IQ of each participant varies, the MSNs accounted for nearly 40% of those variations. According to the researchers, it might be possible for a higher resolution multi-modal data provided by a 7T scanner to account for a further greater proportion of the individual variation.

However, the study does not provide data on the source of this variation, as well as on the reason for some brains to be more connected than others---like genetics or educational upbringing---added Seidlitz. It also lacks data on how these connections strengthen or weaken across development.

Professor Ed Bullmore, Head of Psychiatry at Cambridge, commented: "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."

According to Bullmore, the new technique could also aid us in understanding how the symptoms of mental health disorders like anxiety, depression, or even schizophrenia arise from variations in connectivity within the brain.