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Genes and brain characteristics linked to intelligence

A recent study has identified links between genes, brain structure and intelligence. Published this week in the journal Human Brain Mapping, the work details how the composition of one’s brain coupled with their unique genetic makeup can influence their behaviour and intellect.

A question of intellect

It is well known that intelligence is a hereditary trait, although much remains unknown about the biological factors underpinning this characteristic. Thousands of alleles have been implicated in intelligence, with numerous genome-wide association studies aiming to uncover the mechanisms that explain brain power. Additionally, certain brain characteristics such as network efficiency are thought to contribute to intellect. However, how these factors work in combination remains a mystery.

In the current study, researchers from Ruhr University Bochum, Germany, sought to uncover the interplay between genes, brain characteristics and intelligence.

How big is your brain?

The researchers worked with a group of 557 individuals, most of whom were university students. To assess the volunteers’ intelligence, they were required to sit the Intelligenz-Struktur-Test 2000 R – a standard German intelligence test. The test comprises verbal, numeric and figural reasoning questions, comprehensively mapping the individuals’ skills.

Next, the researchers analysed the volunteers’ genomes for the presence of variants associated with intelligence. With so many genotypes already linked to this neurological trait, the team were able to determine a polygenic score for each individual in the study. These scores were further complemented by brain scans to assess the structure of the cerebral cortex and the organisation of functional networks.

The researchers discovered that those with polygenic scores that predicted high intelligence were more likely to have efficient brain fibre connectivity. Other brain characteristics such as network efficiency and surface area were also implicated. Furthermore, these brain characteristics also showed a link to high intelligence, suggesting that they mediate the association between genes and intellect. However, these results were only found in a limited number of brain regions, namely the frontal, parietal and visual cortex.

Understanding human behaviour

Intelligence is a trait that can impact every aspect of human life, and it is not surprising that researchers are so keen to understand it. That said, the team from Bochum hope that the findings of this study can also help them to understand other human behavioural traits. The interplay between genes, brain structure and behaviour is one that has been overlooked until now, although it is clear that these traits are inherently intertwined.

Lead author Erhan Genç stated: “The broadness and detailed recording of various data in this study is, as far as I am aware, unprecedented. For the first time, we looked at the triad of genes, different brain characteristics and behavioral traits as a whole.” He added, “It would also be interesting if such methods were used in the future with larger cohorts of thousands or tens of thousands of test subjects. Studying the impact of age would also be an interesting future research project.”