Jan Wacker

The role of the nucleus accumbens and rostral anterior cingulate cortex in anhedonia: integration of resting EEG, fMRI, and volumetric techniques.

Anhedonia, the reduced propensity to experience pleasure, is a promising endophenotype and vulnerability factor for several psychiatric disorders, including depression and schizophrenia. In the present study, we used resting electroencephalography, functional magnetic resonance imaging, and volumetric analyses to probe putative associations between anhedonia and individual differences in key nodes of the brains reward system in a non-clinical sample. We found that anhedonia, but not other symptoms of depression or anxiety, was correlated with reduced nucleus accumbens (NAcc) responses to rewards (gains in a monetary incentive delay task), reduced NAcc volume, and increased resting delta current density (i.e., decreased resting activity) in the rostral anterior cingulate cortex (rACC), an area previously implicated in positive subjective experience. In addition, NAcc reward responses were inversely associated with rACC resting delta activity, supporting the hypothesis that delta might be lawfully related to activity within the brains reward circuit. Taken together, these results help elucidate the neural basis of anhedonia and strengthen the argument for anhedonia as an endophenotype for depression.

Acute tryptophan depletion attenuates brain-heart coupling following external feedback

External and internal performance feedback triggers neural and visceral modulations such as reactions in the medial prefrontal cortex and insulae or changes of heart period (HP). The functional coupling of neural and cardiac responses following feedback (cortico-cardiac connectivity) is not well understood. While linear time-lagged within-subjects correlations of single-trial EEG and HP (cardio-electroencephalographic covariance tracing, CECT) indicate a robust negative coupling of EEG magnitude 300 ms after presentation of an external feedback stimulus with subsequent alterations of heart period (the so-called N300H phenomenon), the neurotransmitter systems underlying feedback-evoked cortico-cardiac connectivity are largely unknown. Because it has been shown that acute tryptophan depletion (ATD), attenuating brain serotonin (5-HT), decreases cardiac but not neural correlates of feedback processing, we hypothesized that 5-HT may be involved in feedback-evoked cortico-cardiac connectivity. In a placebo-controlled double-blind cross-over design, 12 healthy male participants received a tryptophan-free amino-acid drink at one session (TRP−) and a balanced amino-acid control-drink (TRP+) on another and twice performed a time-estimation task with feedback presented after each trial. N300H magnitude and plasma tryptophan levels were assessed. Results indicated a robust N300H after TRP+, which was significantly attenuated following TRP−. Moreover, plasma tryptophan levels during TRP+ were correlated with N300H amplitude such that individuals with lower tryptophan levels showed reduced N300H. Together, these findings indicate that 5-HT is important for feedback-induced covariation of cortical and cardiac activity. Because individual differences in anxiety have previously been linked to 5-HT, cortico-cardiac coupling and feedback processing, the present findings may be particularly relevant for futures studies on the relationship between 5-HT and anxiety.

Separating emotion and motivational direction in fear and anger: effects on frontal asymmetry.

State effects on frontal alpha electroencephalograph asymmetry (ASY) are thought to reflect approach and withdrawal motivational tendencies. Although this motivational direction model has inspired a large body of research, efforts to disentangle influences of emotion (EMO) and motivational direction (MOT) on ASY are rare. The authors independently manipulated EMO (fear and anger) and MOT (approach and withdrawal) in a between-subjects design. Irrespective of MOT, anger led to greater changes toward relative left frontal activation (LFA) than did fear. Conversely, higher ratings of negative valence were associated with greater changes toward LFA in withdrawal but with greater changes toward relative right frontal activation in approach. Results are discussed within a model based on behavioral inhibition system-behavioral activation system theory.

Investigating the dopaminergic basis of extraversion in humans: A multilevel approach.

A recent theory suggests that the agency facet of Extraversion (E) is based on brain dopamine (DA). The paucity of human data relevant to this model is probably due to the lack of widely accessible noninvasive psychophysiological indices and well-established behavioral measures sensitive to both E and manipulations of DA activity. Aiming to identify such measures, the authors assessed the electroencephalogram and n-back task performance in groups of introverts and extraverts after administration of either placebo or a selective DA D2 receptor antagonist. As predicted, the antagonists effects on n-back reaction time measures and frontal versus parietal electroencephalogram theta activity were strongly and specifically modulated by E. New research avenues and theoretical extensions suggested by these results are discussed.

Dopamine Effects on Human Error Processing Depend on Catechol-O-Methyltransferase VAL158MET Genotype

Brain dopamine (DA) has been linked to error processing. Because high and low (vs medium) prefrontal cortex (PFC) DA levels may facilitate D2-receptor-related modulations of PFC neural activation patterns, we hypothesized that high and low DA predicts increased error-specific transitions of PFC activity. Male human participants (n = 169) were genotyped for the catechol-O-methyltransferase (COMT) Val158Met polymorphism, associated with low (Val) and medium (Met) PFC DA levels. In addition, DRD2TaqIa and 5-HTTLPR, associated with striatal D2 receptor density and serotonin uptake, respectively, were assessed. Participants received placebo or a selective DA–D2 receptor blocker (sulpiride, 200 mg) and performed a Flanker task. EEG was recorded and decomposed into independent brain components (ICs) using independent component analysis. After errors, participants displayed (1) a negative deflection in ICs source-localized to the proximity of the anterior midcingulate cortex [IC-error-related negativity (IC-ERN)], (2) increased midcingulate cortex IC power in the delta/theta frequency range, and (3) slowing in the subsequent trial [posterror slowing (PES)]. Importantly, all, IC-ERN, delta/theta power, and PES were modulated by COMT × Substance interactions such that the Val allele predicted elevated IC-ERN, delta/theta power, and PES after placebo; this association was reversed under sulpiride. Because low doses of sulpiride presumably increase PFC DA levels, the COMT × Substance interaction supports the hypothesis that low (Val, placebo) and high (Met, sulpiride) versus medium (Val, sulpiride; Met, placebo) DA levels elevate reactivity to errors. Consistent with an influence of serotonin on PFC DA, the COMT × Substance interaction was modulated by 5-HTTLPR.

Dopamine-D2-Receptor Blockade Reverses the Association Between Trait Approach Motivation and Frontal Asymmetry in an Approach-Motivation Context

Individual differences in the behavioral approach system (BAS)—referred to as trait approach motivation or trait BAS)—have been linked to both frontal electroencephalogram (EEG) alpha asymmetry between left and right hemispheres (frontal alpha asymmetry) and brain dopamine. However, evidence directly linking frontal alpha asymmetry and dopamine is scarce. In the present study, female experimenters recorded EEG data in 181 male participants after double-blind administration of either a placebo or a dopamine D2 blocker. As expected, trait BAS was associated with greater left- than right-frontal cortical activity (i.e., greater right- than left-frontal EEG alpha) in the placebo group, but a reversed association emerged in the dopamine-blocker group. Furthermore, frontal alpha asymmetry was associated with a genetic variant known to modulate prefrontal dopamine levels (the catechol-O-methyltransferase Val158Met polymorphism). Finally, each of these effects was significant only in the subgroup of male participants interacting with female experimenters rated as most attractive; this finding suggests that associations between frontal alpha asymmetry and both dopamine and trait BAS are detectable only in approach-motivation contexts.

Defensiveness and anxiety predict frontal EEG asymmetry only in specific situational contexts

Both defensiveness and anxiety have been associated with asymmetrical frontal EEG activity. Recent evidence suggests that context effects in the measurement situation may play a decisive role for the relationship between hemispheric frontal asymmetry and personality. However, until now this hypothesis has not been directly tested. In the present study, participants were confronted with negative or positive personality feedback in a private and a public context. The negative feedback in the public context was assumed to induce fear of social exclusion along with the need for positive self-presentation to restore social acceptance particularly in defensive participants. As predicted, defensive (vs. non-defensive) participants exhibited relative left-frontal activity and high anxious (vs. low anxious) participants exhibited relative right-frontal activity only in this socially threatening negative public situation. These findings indicate that an association between EEG-asymmetry and personality variables may only be observed in situations that are relevant to the personality dimensions of interest.

Sexually dimorphic link between dopamine D2 receptor gene and neuroticism-anxiety

Prior theory-driven research probing the association between dopaminergic candidate genes and human personality has focused on the trait of novelty seeking. Here, we examined the association between the dopamine D2 receptor (DRD2) TaqI A polymorphism and two other personality traits, neuroticism-anxiety and agentic extraversion. We found no significant associations for agentic extraversion. However, for men, but not for women, we observed a strong and specific association between low neuroticism-anxiety and the A1+ allele of the DRD2 TaqI A polymorphism across two independent samples and across two alternative personality scales. We conclude that new theoretical models are needed to account for these and other recent reports of associations between neuroticism-anxiety and brain dopamine, which cannot be interpreted within the traditional framework.

Trait BIS predicts alpha asymmetry and P300 in a Go/No-Go task

Inspired by the revised Behavioural Inhibition System (BIS) theory the present study probed the association between individual differences in Trait BIS and electroencephalogram indicators of conflict processing/inhibition. Sixty‐nine male participants either high or low in Trait BIS completed a Go/No‐Go task while the electroencephalogram was recorded. As expected, Trait BIS was associated with the No‐Go‐anteriorisation of the P300 event‐related potential (i.e. an index of response inhibition presumably generated in the dorsal anterior cingulate—an area implicated in conflict processing) and with No‐ Go‐related changes towards left frontal alpha activity (i.e. presumably more activity in right prefrontal cortex—an area implicated in response inhibition). These findings support the role of conflict processing attributed to BIS functioning in the revised theory. Copyright

The Two Components of Social Desirability and their Relations to Resting Frontal Brain Asymmetry

Abstract. The aim of the present study was to investigate the relationships between resting frontal hemispheric asymmetry (FHA) in the low α band (8-10.25 Hz) and the two components of socially desirable responding, i.e., self-deceptive enhancement (SDE) and impression management (IM), in an opposite-sex encounter. In addition, Big Five facets, self-reports of emotion, and spontaneous eye blink rate (BR), a noninvasive indicator of functional dopamine activity, were assessed. SDE as well as IM were related to relatively greater right-than-left activity in the low α band (i.e., relative left frontal activation; LFA) and to self-reported positive affect (PA), but only SDE was related to BR. We hypothesized that two independent types of motivational approach tendencies underlie individual differences in FHA and PA: affiliative motivation represented by IM and agentic incentive motivation represented by SDE. Whereas the relationship between SDE and PA was mediated by BR, the relationship between SDE and FHA w...