Faster and larger neurons make smarter brains

The properties of individual brain cells have been linked to intelligence for the first time.

Authors: Natalia A. Goriounova1*, Djai B. Heyer1**, René Wilbers1**, Matthijs B. Verhoog1, Michele Giugliano2,3,4, Christophe Verbist2, Joshua Obermayer1, Amber Kerkhofs1, Harriët Smeding3, Maaike Verberne3, Sander Idema4, Johannes C. Baayen4, Anton W. Pieneman1, Christiaan P.J. de Kock1, Martin Klein5, Huibert D. Mansvelder1

*corresponding author
** equal contribution

What makes some people smarter than others? Our brain works through the activity of its almost 100 billion brain cells that each act as a small chip: they collect, process and pass on information in the form of electrical signals. Especially in brain areas that integrate different types of information, such as frontal and temporal lobes, brain cells have larger dendrites - long branches specialized to collect signals. Theoretical studies predict that larger dendrites help cells to initiate electrical signals faster.

Because of difficult access to human living neurons it is completely unknown whether any of these cellular properties actually relate to human intelligence. Previous studies have revealed that people with a higher IQ have a thicker cortex in brain areas such as the frontal and temporal lobes. But does a thicker cortex also contain cells with larger dendrites and do they function differently?

In a collaboration with neurosurgeons and clinical psychologists at VUmc and SEIN, neuroscientists at the VU Amsterdam (CNCR, Faculty of Science) tested whether smarter brains are equipped with faster and larger cells. They studied 46 people who needed surgery for brain tumors or epilepsy. Each took an IQ test before the operation. To access the diseased part deep in the brain, the surgeon also removed small undamaged samples of temporal lobe. These samples still contained living cells and their electrical signals – action potentials- were measured in the lab. The experiments showed that cells from people with a higher IQ have larger dendrites and faster action potentials especially when the neurons need to work hard. Computer models were then used to understand how these findings can lead to more efficient information transfer in human neurons.

Traditionally, research on human intelligence has focused on three main strategies: to study brain structure and function, to find genes associated with intelligence and to study the connection between our mind and behavior. This study is the first to take the single-cell perspective and link cell properties to human intelligence. The findings could help connect separate approaches, and explain how genes for intelligence lead to thicker cortices and faster reaction times in people with higher IQ.

Finally, since our brain has almost 100 billion neurons, even small differences at the level of a single cell shoud be multiplied by this astronomical number. A small step for a single neuron, a giant leap for the computational power of the brain.

Publication in eLife:
Large and fast human pyramidal neurons associate with intelligence.
Authors: Natalia A. Goriounova, Djai B. Heyer, René Wilbers, Matthijs B. Verhoog, Michele Giugliano, Christophe Verbist, Joshua Obermayer, Amber Kerkhofs, Harriët Smeding, Maaike Verberne, Sander Idema, Johannes C. Baayen, Anton W. Pieneman, Christiaan P.J. de Kock, Martin Klein, Huibert D. Mansvelder. , Doi: 10.7554/eLife.41714.