Dr Erhan Genc | Breaking new ground in neuroscientific intelligence research: General knowledge and genetic correlates

Individuals differ with regard to their intellectual abilities and it has been shown that respective differences are highly influenced by structural and functional properties of the brain. In the past, neuroscientific intelligence research was principally concerned with reasoning abilities as its main object of investigation, while neglecting its equally important counterpart general knowledge. In spite of the significant role general knowledge plays for everyday life, its neural foundation largely remains unknown. As part of a large-scale research project, we collected psychometric data, including general knowledge test scores, as well as neuroimaging data from well over 500 healthy individuals. By employing graph analysis, we were able to show that individuals with greater general knowledge had more efficiently connected white matter fiber networks. In contrast, reasoning abilities were associated with cortex volume and functional brain network efficiency. Combined, these findings might indicate different principles of organization for information storage and information processing.

Our research project also included the collection of genetic samples using buccal swaps. In the past, it has been shown that intelligence is a highly heritable trait being influenced by thousands of alleles in cumulative fashion. Polygenic scores (PGS), which combine these small effects into one measure of genetic contribution, explain a considerable amount of this variation, but the underlying biological mechanisms are largely unknown. In our sample, individuals with higher PGS, originally derived from measures of educational attainment and intelligence, indeed scored higher on tests of general intelligence. They also had larger brains and showed higher measures of structural and functional brain network efficiency based on graph analysis. Importantly, we were able to show that the association between PGS and general intelligence was mediated by structural brain network efficiency, but not brain volume or functional network efficiency. However, after refining our analyses to single brain regions, we found the structural and functional network efficiency as well as the volume of specific brain regions, predominantly located in parietal and frontal areas, to be significant mediators. Taken together, these findings represent a crucial step in the endeavor of identifying the missing link between genetic variability and general intelligence.

Poster