Mapping brain structure and personality in late adulthood

Abstract

Cerebral gray matter (GM) volume decreases in normal aging with a parallel increase in intracranial cerebrospinal fluid (CSF) volume. There is considerable interindividual variation in these changes, and the consequences of age-related GM shrinkage and CSF expansion are unclear. The present study examined whether late adulthood brain structural differences are related to differences in temperament and character. Personality structures of 42 healthy aged adults (mean age 60 years) were examined together with global and regional GM, CSF, and white matter (WM) volumes calculated from structural magnetic resonance images using voxel-based morphometry (VBM). A positive relationship was seen between GM volume at the border of the temporal, parietal, and frontal cortices, and self-transcendence, a character personality trait that reflects mature creativity and spiritualism. The relationship remained significant after a conservative correction for multiple comparisons and it was seen both using uncorrected raw values and after a correction for the effects of age and sex. The results suggest that high self-transcendence, which has adaptive advantages in the later part of life, is associated with relatively greater temporal cortical GM volumes.

Introduction

Sudden damage to brain morphology, as exemplified by the case of Phineas Gage (Macmillan, 2000), can cause dramatic changes in personality. Also a slow degeneration of the cortex, as in frontal variant frontotemporal dementia, can present itself predominantly as a change in social behavior and personality (Hodges, 2001). In normal aging, there is a good deal of variability in adulthood personality trajectories (Mroczek and Spiro, 2003), and the cortical gray matter (GM) volume is in a constant state of change across the human life span: the general direction of the change being a global and regional decline in adulthood (Sowell et al., 2003). The developmental GM volume decline can be regionally specific (Giedd et al., 1999, Wilke et al., 2003), and there may be a global process in the decline that is regionally modified, regulated, and determined by a hitherto unknown factor or a combination of factors (Wilke et al., 2003). Aging is also associated with a clear increase in cerebrospinal fluid (CSF) volume, whereas white matter (WM) volume changes in aging are small (Good et al., 2001a).

Recent advances in brain imaging methodology have led to a progressive increase in studies focusing on central markers of human personality. Positron emission tomography (PET), single photon emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI) studies have identified a number of personality traits supposedly associated with central metabolism, neurotransmitter function or cerebral blood flow. Some studies have focused on brain morphology and personality. Structural studies have suggested relationships between low frontal lobe volume and tendency toward psychopathology (Matsui et al., 2000), low supplementary motor area gray matter volume with lack of self-control (Matsui et al., 2002), low whole brain relative volume with neuroticism (Knutson et al., 2001), and large right anterior cingulate cortex volume with fear and anticipatory worry (Pujol et al., 2002). The great majority of personality related functional and structural imaging studies have been carried out in younger subjects.

The issue of age is particularly important in the case of GM volume. In most brain regions, GM is lost more rapidly during the first six decades of life, followed by a subsequent slower decline (Sowell et al., 2003). The age effect is likely to be the dominant factor for GM changes in early and midadulthood. In late adulthood, however, most of the normal age-associated GM decline has occurred although the interindividual variation in GM remains. The present study was carried out to investigate GM, WM, and CSF volume in relation to personality in the later life.