The smarter a person, the fewer connections there are between the neurons in their cerebral cortex. This is the result of a study conducted by neuroscientists working with Dr. Erhan Genç and Christoph Fraenz at Ruhr-Universität Bochum; The study was carried out using a specific neuroimaging technique that provides insights into the brain’s wiring at a microstructural level.
Together with colleagues from the University of New Mexico in Albuquerque, Humboldt University in Berlin and the Lovelace Institute for Biomedical and Environmental Research in Albuquerque, the team from the biopsychology research unit in Bochum published their report in the journal Nature Communications on May 15, 2018.
Intelligence is determined by the number of dendrites
The researchers analyzed the brains of 259 men and women using neurite orientation scatter and density imaging.
This method allowed them to measure the amount of dendrites in the cerebral cortex, that is, extensions of nerve cells that are used by cells to communicate with each other.
Additionally, all participants completed an IQ test. Subsequently, the researchers combined the collected data with each other and discovered: the more intelligent a person, the fewer dendrites there are in their cerebral cortex.
Using an independent, publicly accessible database that had been compiled for the Human Connectome Project, the team confirmed these results in a second sample of about 500 individuals.
Previously conflicting results are thus explained
The new findings provide an explanation of the conflicting results collected in intelligence research to date.
On the one hand, it had already been verified that intelligent people tend to have larger brains.
“The assumption has been that larger brains contain more neurons and, consequently, have more computational power,” says Erhan Genç. However, other studies have shown that — despite their comparatively high number of neurons — the brains of intelligent people demonstrate less neuronal activity during an IQ test than the brains of less intelligent individuals.
“Intelligent brains have lean but efficient neuronal connections”, concludes Erhan Genç. “Thus, they have high mental performance with low neuronal activity.”
