Biological Psychology 87 (2011) 407–413 Contents lists available at ScienceDirect Biological Psychology journa l h o me page: www.elsevier.com/locate/biopsycho Resting posterior minus frontal EEG slow oscillations is associated with extraversion and DRD2 genotype Saskia Koehler a,b,∗ , Jan Wacker c , Thorsten Odorfer d , Andreas Reif d , Jürgen Gallinat e , Andreas J. Fallgatter f , Martin J. Herrmann d a Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Luisenstraße 56, 10099 Berlin, Germany b Department of Psychiatry and Psychotherapy, Charité-Universitätsmedizin Berlin, Campus Mitte, Chariteplatz 1, 10117 Berlin, Germany c Faculty of Psychology, Philipps-Universität Marburg, Gutenbergstraße 18, 35032 Marburg, Germany d Department of Psychiatry, Psychosomatics and Psychotherapy, University of Würzburg, Füchsleinstraße 15, 97080 Würzburg, Germany e St. Hedwig Krankenhaus, Clinic for Psychiatry and Psychotherapy, Charité-Universitätsmedizin Berlin, Große Hamburger Straße 5-11, 10115 Berlin, Germany f Department of Psychiatry and Psychotherapy, University of Tübingen, Osianderstraße 24, 72076 Tübingen, Germany a r t i c l e i n f o Article history: Received 9 October 2010 Accepted 21 May 2011 Available online 7 June 2011 Keywords: Extraversion Personality NEO-PI-R Electroencephalography EEG Resting state Eyes-closed resting condition Slow oscillations Dopamine receptor Genetic polymorphism DRD2 TAQ1A (rs1800497) SNP19 (rs1076560) -141C Ins/Del (rs1799732) a b s t r a c t The agency facet of extraversion has been hypothesized to be based on individual differences in dopamine activity. Recent work suggests that resting posterior minus frontal electroencephalographic (EEG) slow oscillations (delta, theta) is both consistently associated with extraversion and sensitive to dopamine D2 receptor antagonist-induced changes in dopaminergic activity. Here we examine for the first time the interrelations between polymorphisms of the dopamine D2 receptor (DRD2) gene (rs1800497 [previ- ously termed TAQ1A], rs1076560, rs1799732 [-141C Ins/Del]), extraversion and resting posterior minus frontal (Pz–Fz) slow oscillations. As predicted, we found an association between DRD2 and resting Pz–Fz slow oscillations in a sample of 141 individuals participating in an eyes-closed resting EEG session. Moreover, we replicated the association between extraversion and Pz–Fz slow oscillations. Our find- ings strongly suggest that the posterior–frontal distribution of slow oscillations constitutes a useful brain-based intermediate phenotype for investigating the dopaminergic basis of extraversion. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Extraversion, the degree to which individuals can be described as active, assertive, energetic, enthusiastic, outgoing and talkative, constitutes one of the major dimensions of personality (McCrae and John, 1992) and the biological basis of this important trait has been an area of active research for over four decades (Eysenck, 1965; Gray, 1970). Depue and Collins (1999) subdivide extraversion into two facets: sociability/affiliation and agency. Affiliation/sociability is related to delight in interpersonal relationships as well as warmth and cordiality in dealing with other people. By contrast, the agency ∗ Corresponding author at: Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Luisenstraße 56, Haus 1, Berlin, Germany, Tel.: +49 30 2093 1794; fax: +49 30 3810 5505. E-mail address: saskia.koehler@psychologie.hu-berlin.de (S. Koehler). facet of extraversion can be described as a broad motivational dis- position comprising social dominance, assertiveness, enthusiasm, activity, and ambitiousness. Only agency has been theoretically linked to individual differences in mesocorticolimbic dopamine (DA) activity (Depue and Collins, 1999). EEG studies found a correlation between extraversion and low frequency bands (delta and theta power; Knyazev et al., 2003; Knyazev et al., 2002). More recently, Wacker et al. (2006) sug- gested the posterior–frontal distribution of resting EEG activity in the delta and theta band as an easily accessible index of presum- ably DA-linked individual differences in extraversion. This index reflects the difference of slow resting oscillatory EEG activity at the electrode positions Pz and Fz (Pz–Fz slow oscillations). Pz–Fz slow oscillations was subsequently associated with resting slow oscilla- tions in the rostral anterior cingulate cortex (rACC;Chavanon et al., 2010), which in turn predicts Nucleus accumbens reward responses (Wacker et al., 2009). Furthermore, resting Pz–Fz slow oscillations 0301-0511/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.biopsycho.2011.05.006