Personality linked to brain structure

Personality is a multi-faceted quality with numerous possible influencing factors, making it intriguing and yet difficult to measure and study. We are constantly shaped by our experiences and environment.

However, in a recent study published in the journal Social Cognitive and Affective Neuroscience, a team of researchers from the United States, the United Kingdom and Italy observed that different personality traits in individuals are also linked to differences in brain structure.

Psychologists break the immense variety of human personality into five major traits: neuroticism, extraversion, openness, agreeableness and conscientiousness. Using these five traits, scientists in the aforementioned study examined the connection between personality and the anatomy of the cortex, or the outermost layer of the brain.

To do so, they used an imaging dataset of more than 500 healthy individuals between the ages of 22 and 36. The dataset used was made publicly available by the National Institutes of Health as part of the Human Connectome Project, an effort launched to generate a greater understanding for the neural pathways that dictate brain function.

In each individual, they looked at the thickness, area and amount of folding in the cortex.

These are significant indices of brain anatomy because, according to senior author Dr. Luca Passamonti from the Department of Clinical Neurosciences at the University of Cambridge, the brain has an important evolutionary mechanism that allows it to fold upon itself. This folding increases its surface area so that the brain can continue to expand while still fitting into the skull.

“It’s like stretching a folding a rubber sheet — this increases the surface area, but the sheet itself becomes thinner,” he said.

This concept, known as the cortical stretching hypothesis, is a process that occurs throughout human development, from the womb and into adulthood. During brain development, the thickness of the cortex decreases while the area and folding increase.

While observing how these three characteristics of cortex structure correlate to the five major personality traits, researchers found that high levels of neuroticism, marking a possible predisposition for neuropsychiatric disorders, were associated with increased thickness as well as reduced area and folding in certain parts of the cortex, such as the prefrontal-temporal cortices at the front of the brain.

Openness, however, a trait associated with creativity, curiosity and eagerness, was linked to reduced thickness and an increase in area and folding in a similar region of the prefrontal cortices.

Interestingly scientists also found that neuroticism decreases as we grow older (people can better manage their emotions).

In contrast, conscientiousness and agreeableness tend to go up with age (people become more responsible and less hostile as they mature).

Since cortex thickness decreases and folding increases with age as our brains continue to develop, this further supports the discovery that neuroticism and the other major personality traits are influenced by brain anatomy.

The results of the study support the idea that personality is to some degree associated with brain development, a process of maturation that is strongly dictated by genetics.

This conclusion also agrees with the notion that some fundamental personality characteristics can sometimes be recognized in early stages of human development, such as during the infant years.

More importantly, the findings from this study have implications other than a speculation about personality. The results may help us better understand brain disorders.

“Linking how brain structure is related to basic personality traits is a crucial step to improving our understanding of the link between the brain morphology and particular mood, cognitive or behavioral disorders,” Dr. Passamonti said. “We also need to have a better understanding of the relation between brain structure and function in healthy people to figure out what is different in people with neurological and psychiatric disorders.”