Extraversion Is Associated With Lower Brain Beta-Amyloid Deposition in Cognitively Normal Older Adults

Abstract

Emerging evidence suggests that some personality traits may link to the vulnerability to or protection for Alzheimer's disease (AD). A causal mechanism underlying this relationship, however, remains largely unknown. Using ¹⁸F-Florbetaben positron emission tomography (PET) binding to beta-amyloid (Aβ) plaques, a pathological feature of AD, and functional magnetic resonance imaging (fMRI), we investigated pathological and functional correlates of extraversion and neuroticism in a group of healthy young and older subjects. We quantified the level of brain Aβ deposition in older individuals. Brain activity was measured in young adults using a task-switching fMRI paradigm. When we correlated personality scores of extraversion and neuroticism with these pathological and functional measures, higher extraversion, but not neuroticism, was significantly associated with lower global Aβ measures among older adults, accounting for age and sex. This association was present across widespread brain regions. Among young subjects, higher extraversion was associated with lower activity during task switching in the anterior cingulate cortex, left anterior insular cortex, left putamen, and middle frontal gyrus bilaterally, while higher neuroticism was associated with increased activity throughout the brain. The present results suggest that possibly via efficient neuronal activity, extraversion, one of the lifelong personality traits, may confer the protective mechanism against the development of Aβ pathology during aging.

Keywords: Alzheimer’s disease risk factor; beta amyloid deposition; extraversion; neuroticism; personality.

Figure 1

Extraversion is associated with lower amyloid deposition in cognitively normal older adults. (A) Association between voxel-wise standardized uptake value ratio (SUVR) measures and extraversion among cognitively normal older adults. Scale represents voxel-wise SUVR measures. Regions highlighted in yellow represent voxels whose SUVR values are equal to or are greater than 1. Regions highlighted in cyan represent suprathreshold voxels showing a significant negative association between extraversion and amyloid burden. Regions highlighted in green indicate an overlap between amyloid deposition and a significant negative association with extraversion scores. (B) Extraversion scores are associated with lower amyloid deposition as quantified by a global amyloid index that represents the mean cortical amyloid burden. (C) A significant negative association between extraversion and amyloid deposition is found using the mean amyloid accumulation in posterior cingulate cortex (Post. Cingulate). (D) Extraversion scores (residual values) are associated with better, although at a trend level, memory performance (residual values) among cognitively normal older adults. (E) Extraversion scores are not associated with processing speed. Age and sex were controlled in the analyses.

Figure 2

Differential brain activity patterns in association with extraversion and neuroticism among young adults. (A) Task-evoked brain activity during executive control tasks in relation to extraversion scores among young adults. Regions in green indicate suprathreshold voxels showing lower brain activity in relation to higher extraversion scores for single task vs. baseline and dual-task vs. baseline comparisons. (B) Task-evoked brain activity during executive control tasks in relation to neuroticism scores among young adults. Regions in warm colors indicate suprathreshold voxels showing increased brain activity in relation to higher neuroticism scores for single task vs. baseline and dual-task vs. baseline comparisons and dual vs. single task contrasts. Scale represents T values.