Personality and the Brain

Amber Badgerow

October 10, 2011

PSY 213

Olmsted

Personality and the Brain

Question:

Much research has been conducted to discover how personality is formed. Most research, thus far, has been aimed at discovering the role experiences or genes play in personality and, only recently, have scientists begun exploring the brain’s involvement in personality. What brain structures have been associated with different personality types and traits?

Prediction:

The brain’s frontal lobes should be involved in personality since it is the area concerned with memory, judgment, social behavior, etc. All these have been concluded to be critical for personality formation. The limbic system may also contribute to personality because it has also been implicated in memory and emotions.

Article 1: “Testing Predictions From Personality Neuroscience: Brain Structure and the Big Five”

This article (found via the Science Direct database from PCC) by Colin G. DeYoung, Jacob B. Hirsh, Matthew S. Shane, Xenophon Papademetris, Nallakkandi Rajeevan, and Jeremy R. Gray, discusses the study on the relative volume of different brain regions affiliated with the five general dimensions of personality, which are openness, conscientiousness, extraversion, agreeableness, and neuroticism. They found, using a whole-brain magnetization-prepared rapid gradient-echo image (MPRAGE) to produce a view of brain structure, that there were in fact differences in volume associated with the different personality dimensions. Openness (those who tend to easily and efficiently process conceptual and noncognitive information) was the only personality that did not show considerable association with relative brain volume, but there was a slight correlation with a region of the parietal cortex, involved in attention control and working memory, which would be consistent based on the traits of the personality. Conscientiousness (those who can suppress impulses to unnecessarily pursue goals and obey rules) had an association with increased volume in the lateral prefrontal cortex, which plays a critical part in accomplishing devised actions and retaining information in working memory. The extraversion dimension of personality (those who primarily feel positive emotions), showed larger volume of the medial orbitofrontal cortex- involved in classifying the worth of rewards from stimuli. Agreeableness (those who are attentive to what others want, need, and deserve) was strongly related to an increased volume in the fusiform gyrus and in the retrosplenial region of the posterior cingulate cortex, which is involved in comprehending other people’s beliefs. The study also showed that agreeableness demonstrated a decreased volume in the superior temporal sulcus- implicated in understanding the purposes and actions of others- and in the bordering superior temporal gyrus. Neuroticism (those who typically feel negative emotions) showed a connection to smaller volume in the left medial temporal lobe (incorporating the posterior hippocampus and portions of the basal ganglia and midbrain), in an area of the right precentral gyrus, and in the right dorsomedial prefrontal cortex, which is associated with controlling emotions and judging oneself. There was also a correlation to larger volume in an area of the cerebellum, in a region of the middle temporal gyrus, in an area of the left hemisphere that extended to the caudate, and in an area, that spread into the cingulate gyrus white matter, of the mid-cingulate cortex- involved in reacting to pain and identifying error.

Article 2: “Individual Differences in Personality Traits Reflect Structural Variance in Specific Brain Regions”

This article was found on the University of Minnesota website. Simona Gardini, C. Robert Cloninger, and Annalena Venneri focus their research on dimensions of personality that are categorized differently than the previous article- harm avoidance, novelty seeking, persistence, and reward dependence. The study uses association analysis between MRI scans, used to measure grey matter volume, and subjects’ personality trait scores. The results from the study support other research into personality and brain structure. Harm avoidance (characterized by fear, extreme worry, fatigue, and shyness) was associated with decreased volume in the left precuneus, inferior parietal lobule, middle frontal gyrus, middle occipital gyrus, and the inferior frontal gyrus. These areas of the orbitofrontal cortex are implicated in the reaction to emotion and reward. Novelty seeking (identified by impulsiveness, untidiness, indulgence, and exploratory excitability) correlated with increased volume in the posterior cingulate gyrus, right superior gyrus, and middle frontal gyrus, which are indicated in absolute attention and focusing attention to the outside of the visual field. Persistence (portrayed by a hard working, perfectionistic, ambitious, and eager to achieve attitude) was related to increased volume in the parahippocampal gyrus, right paracentral lobule, and left precuneus, which is associated in various cognitive functions (possibly in the evaluation of the self). Reward dependence (continuing behaviors related to reinforcement) was connected with decreased volume in the right caudate and rectal frontal gyrus, which are involved in emotional reward, controlling behavior, and motivation.

Source Validity:

Both sources are reliable with credentialed authors and an adequate subject group (study one had 116 participants and study two had 85 participants). The only matter, noted by the authors, was that the second study mentioned used methods to form the 3D brain image that had been questioned by others. However, the methods have proven very useful and are acceptable.

Reflection on Hypothesis:

My hypothesis, though very simplified, was wholly supported by my research. Frontal regions and the
limbic system of the brain have both been indicated in personality. There is still more research required to
further understand the relationship between the brain and personality.