The more intelligent a person, the fewer connections there are between the neurons in his cerebral cortex, according to new research.
For the study, researchers at the Ruhr-Universität Bochum in Germany, the University of New Mexico in Albuquerque, Humboldt University of Berlin, and the Lovelace Biomedical and Environmental Research Institute in Albuquerque used a specific neuroimaging technique that provides insights into the wiring of the brain on a microstructural level.
Researchers analyzed the brains of 259 men and women using neurite orientation dispersion and density imaging. This method enabled them to measure the amount of dendrites in the cerebral cortex. Dendrites are extensions of nerve cells that are used by the cells to communicate with each other, researchers explained.
In addition, all participants completed an IQ test.
From this, the researchers discovered that the more intelligent a person, the fewer dendrites there are in their cerebral cortex.
Using an independent, publicly accessible database, which had been compiled for the Human Connectome Project, the research team confirmed these results in a second sample of around 500 individuals.
The new findings provide an explanation of conflicting results gathered in intelligence research to date, according to the researchers.
For one, it had been previously thought that intelligent people tend to have larger brains.
“The assumption has been that larger brains contain more neurons and, consequently, possess more computational power,” said Dr. Erhan Genç of the Ruhr-Universität Bochum. “However, other studies had shown that — despite their comparatively high number of neurons — the brains of intelligent people demonstrated less neuronal activity during an IQ test than the brains of less intelligent individuals.”
“Intelligent brains possess lean, yet efficient neuronal connections,” he added. “Thus, they boast high mental performance at low neuronal activity.”
The study was published in the journal Nature Communications.
Source: Ruhr-Universität Bochum