Neurobiological correlates of introversion-extraversion with activation-state brain SPECT imaging

ABSTRACT:
Here we explored the relationship between personality and regional cerebral blood flow using the introversion-extraversion subscale of the Keirsey temperament scale (KTS-II) and brain single-photon computed emission tomography (SPECT) in former professional American football players. We administered the KTS-II to a cohort of 78 (mean age ± SD) retired professional football players who underwent a comprehensive evaluation in an outpatient psychiatric clinic which included SPECT imaging as part of a study measuring the effects of repetitive subconcussive impacts on brain function. Using SPSS, whole brain average and region of interest (ROI) analysis were performed on the subscale of introversion-extraversion (introversion, n=26; extraversion, n=38; mixed, n=8; neither, n=6). Introverts show elevated metabolic activity across multiple brain regions including the anterior cingulate gyrus, caudate, temporal lobes, hippocampus, inferior parietal lobe and the cerebellar vermis IX. Alternatively, extraverts show lower overall global activity, with reductions in the inferior orbital and prefrontal cortices. The present study demonstrates distinct regional activity profiles unique to extraversion and introversion during a brain activation-task which has not been previously reported. Further exploration into mapping the neural pathways that are associated with introversion-extraversion may extrapolate meaningful correlations between these personality dimensions and brain physiology.