Individuals with a neurotic personality type may have reduced brain plasticity during the performance of working memory tasks that may affect their ability to store memories, say US researchers in findings that show the opposite effect in people with a conscientious personality.
In a functional magnetic resonance imaging (fMRI) study, investigators found that neuroticism was associated with weaker connectivity between two brain regions during performance of a working memory task, whereas conscientiousness was linked to stronger connectivity in healthy adults.
"Our results demonstrate that neural network plasticity, as measured by changes in effective connectivity, links individual differences in behaviour and cognitive efficiency," the investigators write.
The study was published online July 20 in Human Brain Mapping.
Higher Neuroticism, Poorer Memory
Study author Sophia Frangou, MD, PhD, Department of Psychiatry, Icahn Medical Institute, New York City, told Medscape Medical News what inspired the research.
"We know that there are differences between individuals in the way that they perform cognitively," she said.
"We know that there are differences in personality traits between different people, and that personality traits influence the way individuals perform on cognitive testing, especially things that are very executive, like working memory...and we also know that personality affects or is associated with brain structure, which is a more stable feature of our brain."
"What was missing is a way of putting everything together that makes mechanistic sense, in the sense of, Why are these variables all related to each other?" she added.
For the study, 40 healthy adults performed the n-back working memory task while undergoing fMRI.
Because working memory consistently involves the dorsolateral prefrontal (DLPFC), parietal (PAR), and anterior cingulate cortices, the researchers used dynamic causal modeling to examine task- related changes in effective connectivity, which is a measure of short-term brain plasticity, between these regions.
In addition, participants completed the Neuroticism–Extraversion–Openness Personality Inventory–Revised personality questionnaire, which covers the domains of neuroticism, conscientiousness, agreeableness, extraversion, and openness to experience, and the Wechsler Adult Intelligence Scale–Revised.
The results indicated that effective connectivity in the forward connection from the right PAR to the right DLPFC was significantly associated with performing the working memory task (P < .002) and that the degree to which the task modulated that connectivity was significantly associated with improved response times (P = .04).
Further analysis revealed that higher neuroticism scores were associated with significantly reduced working memory task modulation of the right PAR to right DLPFC forward connection, whereas the opposite effect was seen with higher conscientiousness scores (P = .001 for both).
There was no association between agreeableness, extraversion, openness to experience, age, sex, IQ, and the degree of modulation of the right PAR to the right DLPFC connection.
Although acknowledging that the study was not specifically designed to determine the links between personality type and brain plasticity in working memory, Dr Frangou noted that previous studies have indicated that more neurotic individuals have lower activation in the PAR and DLPFC and have slightly smaller frontal cortices. Moreover, the opposite has been observed in people who are more conscientious.
"The idea is that, as we grow up, there's an interplay between the basic blueprint of our brain, and that interacts through experience to build these personality traits over a long period of time, and this affects the way that we are put together," she said.
The question then becomes: Why would that affect specifically a person's working memory?
"The answer to that is that these more long-term, if you want, traitlike features of your brain, which are reflected in your personality, seem to also constrain the amount of plasticity that your brain has," she added.
Using the metaphor of a house, she said: "Once you have your supporting walls, you can do a little bit in changing the interior, if you see that as a transient change in how you organize the interior of the house, but the basic components are there, and they either allow you to do a lot of things within them, or they may prevent you and make it more difficult."
The next steps in research include determining whether the findings can be incorporated into methods for training individuals to improve their working memory.
"Nobody has tried to see if reducing neuroticism can actually improve working memory; these are the ideas that we're playing with. People have tried to see if they can improve just working memory, and they found that neuroticism is a barrier," she said.
"What we do know about neuroticism is that, across the board, it's one of the personality traits that puts you at risk for a very large number of negative outcomes, not just working memory and not just mental health but physical health as well.
"One of the ideas that we are toying with is to get people to control their neuroticism and see if the change can be long term and if it can improve cognition and perhaps coping styles more generally. That's where we might be going next," Dr Frangou said.
Dean Hartley, PhD, director of science initiatives at the Alzheimer's Association, commented that the question of how personality can become encoded in the brain is extremely promising in terms of research.
"The study is quiet fascinating for thinking that we might have that facility, and I think functional MRI will play a greater role in both understanding our basic biology but, more importantly, as we go into the medical setting, what is actually going wrong in the brain," Dr Hartley told Medscape Medical News.
He noted that the findings should be interpreted with caution, owing to the small sample size and because the determination of personality types was based on a self-report questionnaire.
Nevertheless, he said: "I think this is the newer frontier of understanding these large neural networks and how they work together and, particularly, how they work together or decline in disease states."
"The Alzheimer's Association is always advocating for more research. That will give us the answers, not only to problems like this but also how we get to treatments for Alzheimer's disease.
"To me, the fundamental thing here is always to keep the scientists funded to undertake interesting studies like this, which may add to our understanding Alzheimer's disease," he added.
The authors and Dr Hartley report no relevant financial relationships.
Hum Brain Mapp. Published online July 20, 2015. Abstract
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Cite this: Neuroticism Linked to Memory Problems - Medscape - Jul 27, 2015.