Neuroanatomical correlates of personality in the elderly

Abstract

Extraversion and neuroticism are two important and frequently studied dimensions of human personality. They describe individual differences in emotional responding that are quite stable across the adult lifespan. Neuroimaging research has begun to provide evidence that neuroticism and extraversion have specific neuroanatomical correlates within the cerebral cortex and amygdala of young adults. However, these brain areas undergo alterations in size with aging, which may influence the nature of these personality factor-brain structure associations in the elderly. One study in the elderly demonstrated associations between perisylvian cortex structure and measures of self transcendence [Kaasinen, V., Maguire, R.P., Kurki, T., Bruck, A., Rinne, J.O., 2005. Mapping brain structure and personality in late adulthood. NeuroImage 24, 315-322], but the neuroanatomical correlates of extraversion and neuroticism, or other measures of the Five Factor Model of personality have not been explored. The purpose of the present study was to investigate the structural correlates of neuroticism and extraversion in healthy elderly subjects (n=29) using neuroanatomic measures of the cerebral cortex and amygdala. We observed that the thickness of specific lateral prefrontal cortex (PFC) regions, but not amygdala volume, correlates with measures of extraversion and neuroticism. The results suggest differences in the regional neuroanatomic correlates of specific personality traits with aging. We speculate that this relates to the influences of age-related structural changes in the PFC.

Figure 1. Significant Correlations of Cortical Thickness and Extraversion in the Lateral Prefrontal Cortex

(A) Colorized statistical map superimposed upon a partially inflated group average cortical surface. The lateral aspect the right hemisphere is shown. A significant positive correlation of cortical thickness with extraversion was found in the superior frontal cortex (SFC). (B) Colorized statistical map superimposed upon a partially inflated group average cortical surface. The lateral aspect the left hemisphere is shown with a significant positive correlation between cortical thickness and extraversion in the anterior parts of the middle frontal cortex (MFC). Dark gray regions are sulci, light gray are gyri. Colorized scale bars show the p-value for positive (red-yellow) and negative (blue) correlations. (C) Scatter plot and regression line demonstrating a significant positive correlation between right SFC thickness and extraversion. These values were extracted from the peak surface point of the SFC shown in (A). (D) Scatter plot and regression line from the same MFG site in (B).

Figure 2. Significant Correlations of Cortical Thickness and Neuroticism in the Right Hemisphere

(A) Colorized statistical map superimposed upon a partially inflated group average cortical surface. The lateral aspect the right hemisphere is shown. Significant inverse correlations of cortical thickness with neuroticism were found in the superior and inferior frontal cortex (SFC, IFC). A significant positive correlation between neuroticism and cortical thickness was found in the anterior temporal cortex (ATC). Dark gray regions are sulci, light gray are gyri. Colorized scale bars show the p-value for positive (red-yellow) and negative (blue) correlations. (B) Scatter plot and regression line demonstrating a significant inverse correlation between SFC thickness and neuroticism. These values were extracted from the peak surface point of the SFC locus shown in (A). (C) Scatter plot and regression line from the peak of the IFC locus in (A). (D) Scatter plot and regression line from peak of the ATC locus in (A).

Figure 3. Significant Correlations of Cortical Thickness and Openness in the Parietal Cortex

(A) Colorized statistical map superimposed upon a partially inflated group average cortical surface. The lateral aspect the left hemisphere is shown. Significant inverse correlations of cortical thickness with openness were found in the inferior parietal cortex (IPC). Dark gray regions are sulci, light gray are gyri. Colorized scale bars show the p-value for positive (red-yellow) and negative (blue) correlations. (B) Scatter plot and regression line demonstrating a significant inverse correlation between IPC thickness and neuroticism. These values were extracted from the peak surface point of the IPC shown in (A).