Prefrontal cortex glutamate and extraversion

Abstract

Extraversion is considered one of the core traits of personality. Low extraversion has been associated with increased vulnerability to affective and anxiety disorders. Brain imaging studies have linked extraversion, approach behaviour and the production of positive emotional states to the dorsolateral prefrontal cortex (DLPFC) and glutamatergic neurotransmission. However, the relationship between extraversion and glutamate in the DLPFC has not been investigated so far. In order to address this issue, absolute glutamate concentrations in the DLPFC and the visual cortex as a control region were measured by 3-Tesla proton magnetic resonance spectroscopy (1H-MRS) in 29 subjects with high and low extraversion. We found increased glutamate levels in the DLPFC of introverts as compared with extraverts. The increased glutamate concentration was specific for the DLPFC and negatively associated with state anxiety. Although preliminary, results indicate altered top-down control of DLPFC due to reduced glutamate concentration as a function of extraversion. Glutamate measurement with 1H-MRS may facilitate the understanding of biological underpinnings of personality traits and psychiatric diseases associated with dysfunctions in approach behaviour and the production of positive emotional states.

Fig. 1

Voxel positions shown on typical brain MDEFT images; upper panel: left dorsolateral prefrontal cortex; lower panel: visual cortex.

Fig. 2

Bar diagrams show DLPFC glutamate concentrations in extraverts and introverts. A significant difference between the two groups was observed (P= 0.044). DLPFC = dorsolateral prefrontal cortex.

Fig. 3

Bar diagrams show glutamate concentrations in DLPFC and the control region (VC) in extraverts and introverts. A difference in glutamate concentration between the two regions was observed in introverts (P = 0.054), but not in extraverts. DLPFC = dorsolateral prefrontal cortex; VC = visual cortex.

Fig. 4

Scatterplot of DLPFC glutamate concentrations and state anxiety (STAI 1) scores in extraverts and introverts. A significant negative correlation was observed in introverts, but not in extraverts. *P < 0.005.