Personality predicts brain responses to cognitive demands

Abstract

Eysenck (1981) proposed that the personality dimension of introversion- extraversion (E) reflects individual differences in a cortical arousal system modulated by reticulothalamic- cortical pathways: it is chronically more active in introverts relative to extraverts and influences cognitive performance in interaction with task parameters. A circuit with connections to this system, including the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate (AC) cortex, has been identified in studies applying functional magnetic resonance imaging (fMRI) to a broad range of cognitive tasks. We examined the influence of E, assessed with the Eysenck Personality Questionnaire-Revised (Eysenck and Eysenck, 1991), in fMRI activity during an "n-back" task involving four memory loads (0-, 1-, 2-, and 3-back) and a rest condition in healthy men. To confirm the specificity of E effects, we also examined the effects of neuroticism and psychoticism (P) scores. We observed that, as predicted by Eysenck's model, the higher the E score, the greater the change in fMRI signal from rest to the 3-back condition in the DLPFC and AC. In addition, E scores were negatively associated with resting fMRI signals in the thalamus and Broca's area extending to Wernicke's area, supporting the hypothesized (negative) relationship between E and resting arousal. P scores negatively correlated with resting fMRI signal in the globus pallidus-putamen, extending previous findings of a negative relationship of schizotypy to striatal activity seen with older neuroimaging modalities to fMRI. These observations suggest that individual differences affect brain responses during cognitive activity and at rest and provide evidence for the hypothesized neurobiological basis of personality.

Figure 1.

Increase in activity from rest to 0-, 1-, 2-, and 3-back in right DLPFC (a) and AC (b) as a function of individual E score. Memory load-related fMRI signal changes (increases from rest) in right DLPFC (c) and AC (d) in groups with high (≥17) and low (≤9) E scores. e, Activation, thresholded at p < 0.001 (uncorrected), in three individual subjects with E scores of 4 (left), 15 (middle), and 21 (right), superimposed on their own individual structural images. I, Introversion. Color bar shows SPM-derived T values. Task load-related activity in the DLPFC and AC, but not in superior parietal cortex, varied systematically with E. Axial view with associated z coordinates is shown; left hemisphere is shown on the left.

Figure 2.

Localized personality correlates in the globally normalized resting signal intensity related to E. a, Regression map in SPM-derived T values thresholded at p < 0.005 (uncorrected) and superimposed on the average structural image. Color bar shows the strength of the correlation with E. Axial view with associated z coordinates is shown; left hemisphere is shown on the left. Localized resting fMRI signal in relation to intersubject local mean intensity (y-axis) in Wernicke's area (b), cuneus (c), and left (d) and right (e) thalamus as a function of E (x-axis). Graphs show SPSS-derived r values and probabilities.

Figure 3.

Localized personality correlates in the globally normalized resting signal intensity related to P. a, Regression map in SPM-derived T scores thresholded at p < 0.005 (uncorrected) and superimposed on the average structural image. Color bar shows the strength of the correlation with P. Axial view with associated z coordinates is shown; left hemisphere is shown on the left. Localized resting fMRI signal in relation to intersubject local mean intensity (y-axis) in left (b) and right (c) global pallidus as a function of P (x-axis). Graphs show SPSS-derived r values and probabilities.