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1.  Genetic variation of the RASGRF1 regulatory region affects human hippocampus-dependent memory 
The guanine nucleotide exchange factor RASGRF1 is an important regulator of intracellular signaling and neural plasticity in the brain. RASGRF1-deficient mice exhibit a complex phenotype with learning deficits and ocular abnormalities. Also in humans, a genome-wide association study has identified the single nucleotide polymorphism (SNP) rs8027411 in the putative transcription regulatory region of RASGRF1 as a risk variant of myopia. Here we aimed to assess whether, in line with the RASGRF1 knockout mouse phenotype, rs8027411 might also be associated with human memory function. We performed computer-based neuropsychological learning experiments in two independent cohorts of young, healthy participants. Tests included the Verbal Learning and Memory Test (VLMT) and the logical memory section of the Wechsler Memory Scale (WMS). Two sub-cohorts additionally participated in functional magnetic resonance imaging (fMRI) studies of hippocampus function. 119 participants performed a novelty encoding task that had previously been shown to engage the hippocampus, and 63 subjects participated in a reward-related memory encoding study. RASGRF1 rs8027411 genotype was indeed associated with memory performance in an allele dosage-dependent manner, with carriers of the T allele (i.e., the myopia risk allele) showing better memory performance in the early encoding phase of the VLMT and in the recall phase of the WMS logical memory section. In fMRI, T allele carriers exhibited increased hippocampal activation during presentation of novel images and during encoding of pictures associated with monetary reward. Taken together, our results provide evidence for a role of the RASGRF1 gene locus in hippocampus-dependent memory and, along with the previous association with myopia, point toward pleitropic effects of RASGRF1 genetic variations on complex neural function in humans.
doi:10.3389/fnhum.2014.00260
PMCID: PMC4010733  PMID: 24808846
RASGRF1; hippocampus; episodic memory; genetic variation; fMRI
2.  Effects of AKAP5 Pro100Leu Genotype on Working Memory for Emotional Stimuli 
PLoS ONE  2013;8(1):e55613.
Recent investigations addressing the role of the synaptic multiadaptor molecule AKAP5 in human emotion and behavior suggest that the AKAP5 Pro100Leu polymorphism (rs2230491) contributes to individual differences in affective control. Carriers of the less common Leu allele show a higher control of anger as indicated by behavioral measures and dACC brain response on emotional distracters when compared to Pro homozygotes. In the current fMRI study we used an emotional working memory task according to the n-back scheme with neutral and negative emotional faces as target stimuli. Pro homozygotes showed a performance advantage at the behavioral level and exhibited enhanced activation of the amygdala and fusiform face area during working memory for emotional faces. On the other hand, Leu carriers exhibited increased activation of the dACC during performance of the 2-back condition. Our results suggest that AKAP5 Pro100Leu effects on emotion processing might be task-dependent with Pro homozygotes showing lower control of emotional interference, but more efficient processing of task-relevant emotional stimuli.
doi:10.1371/journal.pone.0055613
PMCID: PMC3558499  PMID: 23383244
3.  Trait anxiety modulates fronto-limbic processing of emotional interference in borderline personality disorder 
Previous studies of cognitive alterations in borderline personality disorder (BPD) have yielded conflicting results. Given that a core feature of BPD is affective instability, which is characterized by emotional hyperreactivity and deficits in emotion regulation, it seems conceivable that short-lasting emotional distress might exert temporary detrimental effects on cognitive performance. Here we used functional magnetic resonance imaging (fMRI) to investigate how task-irrelevant emotional stimuli (fearful faces) affect performance and fronto-limbic neural activity patterns during attention-demanding cognitive processing in 16 female, unmedicated BPD patients relative to 24 age-matched healthy controls. In a modified flanker task, emotionally negative, socially salient pictures (fearful vs. neutral faces) were presented as distracters in the background. Patients, but not controls, showed an atypical response pattern of the right amygdala with increased activation during emotional interference in the (difficult) incongruent flanker condition, but emotion-related amygdala deactivation in the congruent condition. A direct comparison of the emotional conditions between the two groups revealed that the strongest diagnosis-related differences could be observed in the dorsal and, to a lesser extent, also in the rostral anterior cingulate cortex (dACC, rACC) where patients exhibited an increased neural response to emotional relative to neutral distracters. Moreover, in the incongruent condition, both the dACC and rACC fMRI responses during emotional interference were negatively correlated with trait anxiety in the patients, but not in the healthy controls. As higher trait anxiety was also associated with longer reaction times (RTs) in the BPD patients, we suggest that in BPD patients the ACC might mediate compensatory cognitive processes during emotional interference and that such neurocognitive compensation that can be adversely affected by high levels of anxiety.
doi:10.3389/fnhum.2013.00054
PMCID: PMC3585713  PMID: 23459637
borderline personality disorder; cognition-emotion interaction; anxiety; fMRI; amygdala; anterior cingulate cortex
4.  Motivational salience and genetic variability of dopamine D2 receptor expression interact in the modulation of interference processing 
Dopamine has been implicated in the fine-tuning of complex cognitive and motor function and also in the anticipation of future rewards. This dual function of dopamine suggests that dopamine might be involved in the generation of active motivated behavior. The DRD2 TaqIA polymorphism of the dopamine D2 receptor gene (rs1800497) has previously been suggested to affect striatal function with carriers of the less common A1 allele exhibiting reduced striatal D2 receptor density and increased risk for addiction. Here we aimed to investigate the influences of DRD2 TaqIA genotype on the modulation of interference processing by reward and punishment. Forty-six young, healthy volunteers participated in a behavioral experiment, and 32 underwent functional magnetic resonance imaging (fMRI). Participants performed a flanker task with a motivation manipulation (monetary reward, monetary loss, neither, or both). Reaction times (RTs) were shorter in motivated flanker trials, irrespective of congruency. In the fMRI experiment motivation was associated with reduced prefrontal activation during incongruent vs. congruent flanker trials, possibly reflecting increased processing efficiency. DRD2 TaqIA genotype did not affect overall RTs, but interacted with motivation on the congruency-related RT differences, with A1 carriers showing smaller interference effects to reward alone and A2 homozygotes exhibiting a specific interference reduction during combined reward (REW) and punishment trials (PUN). In fMRI, anterior cingulate activity showed a similar pattern of genotype-related modulation. Additionally, A1 carriers showed increased anterior insula activation relative to A2 homozygotes. Our results point to a role for genetic variations of the dopaminergic system in individual differences of cognition-motivation interaction.
doi:10.3389/fnhum.2013.00250
PMCID: PMC3672681  PMID: 23760450
DRD2; TaqIA; dopamine; genetic; motivation; interference processing; flanker; fMRI
5.  An fMRI Study on the Role of Serotonin in Reactive Aggression 
PLoS ONE  2011;6(11):e27668.
Reactive aggression after interpersonal provocation is a common behavior in humans. Little is known, however, about brain regions and neurotransmitters critical for the decision-making and affective processes involved in aggressive interactions. With the present fMRI study, we wanted to examine the role of serotonin in reactive aggression by means of an acute tryptophan depletion (ATD). Participants performed in a competitive reaction time task (Taylor Aggression Paradigm, TAP) which entitled the winner to punish the loser. The TAP seeks to elicit aggression by provocation. The study followed a double-blind between-subject design including only male participants. Behavioral data showed an aggression diminishing effect of ATD in low trait-aggressive participants, whereas no ATD effect was detected in high trait-aggressive participants. ATD also led to reduced insula activity during the decision phase, independently of the level of provocation. Whereas previous reports have suggested an inverse relationship between serotonin level and aggressive behavior with low levels of serotonin leading to higher aggression and vice versa, such a simple relationship is inconsistent with the current data.
doi:10.1371/journal.pone.0027668
PMCID: PMC3218006  PMID: 22110714
6.  The Role of Executive Functions in the Control of Aggressive Behavior  
An extensive literature suggests a link between executive functions and aggressive behavior in humans, pointing mostly to an inverse relationship, i.e., increased tendencies toward aggression in individuals scoring low on executive function tests. This literature is limited, though, in terms of the groups studied and the measures of executive functions. In this paper, we present data from two studies addressing these issues. In a first behavioral study, we asked whether high trait aggressiveness is related to reduced executive functions. A sample of over 600 students performed in an extensive behavioral test battery including paradigms addressing executive functions such as the Eriksen Flanker task, Stroop task, n-back task, and Tower of London (TOL). High trait aggressive participants were found to have a significantly reduced latency score in the TOL, indicating more impulsive behavior compared to low trait aggressive participants. No other differences were detected. In an EEG-study, we assessed neural and behavioral correlates of error monitoring and response inhibition in participants who were characterized based on their laboratory-induced aggressive behavior in a competitive reaction time task. Participants who retaliated more in the aggression paradigm and had reduced frontal activity when being provoked did not, however, show any reduction in behavioral or neural correlates of executive control compared to the less aggressive participants. Our results question a strong relationship between aggression and executive functions at least for healthy, high-functioning people.
doi:10.3389/fpsyg.2011.00152
PMCID: PMC3130185  PMID: 21747775
reactive aggression; executive functions; Eriksen Flanker task; stop-signal task; Taylor aggression paradigm; Tower of London
7.  Genetic Variation of the Serotonin 2a Receptor Affects Hippocampal Novelty Processing in Humans 
PLoS ONE  2011;6(1):e15984.
Serotonin (5-hydroxytryptamine, 5-HT) is an important neuromodulator in learning and memory processes. A functional genetic polymorphism of the 5-HT 2a receptor (5-HTR2a His452Tyr), which leads to blunted intracellular signaling, has previously been associated with explicit memory performance in several independent cohorts, but the underlying neural mechanisms are thus far unclear. The human hippocampus plays a critical role in memory, particularly in the detection and encoding of novel information. Here we investigated the relationship of 5-HTR2a His452Tyr and hippocampal novelty processing in 41 young, healthy subjects using functional magnetic resonance imaging (fMRI). Participants performed a novelty/familiarity task with complex scene stimuli, which was followed by a delayed recognition memory test 24 hours later. Compared to His homozygotes, Tyr carriers exhibited a diminished hippocampal response to novel stimuli and a higher tendency to judge novel stimuli as familiar during delayed recognition. Across the cohort, the false alarm rate during delayed recognition correlated negatively with the hippocampal novelty response. Our results suggest that previously reported effects of 5-HTR2a on explicit memory performance may, at least in part, be mediated by alterations of hippocampal novelty processing.
doi:10.1371/journal.pone.0015984
PMCID: PMC3022731  PMID: 21267461
8.  A Potential Role for a Genetic Variation of AKAP5 in Human Aggression and Anger Control 
The A-kinase-anchoring protein 5 (AKAP5), a post-synaptic multi-adaptor molecule that binds G-protein-coupled receptors and intracellular signaling molecules has been implicated in emotional processing in rodents, but its role in human emotion and behavior is up to now still not quite clear. Here, we report an association of individual differences in aggressive behavior and anger expression with a functional genetic polymorphism (Pro100Leu) in the human AKAP5 gene. Among a cohort of 527 young, healthy individuals, carriers of the less common Leu allele (15.6% allele frequency) scored significantly lower in the physical aggression domain of the Buss and Perry Aggression Questionnaire and higher in the anger control dimension of the state-trait anger expression inventory. In a functional magnetic resonance imaging experiment we could further demonstrate that AKAP5 Pro100Leu modulates the interaction of negative emotional processing and executive functions. In order to investigate implicit processes of anger control, we used the well-known flanker task to evoke processes of action monitoring and error processing and added task-irrelevant neutral or angry faces in the background of the flanker stimuli. In line with our predictions, Leu carriers showed increased activation of the anterior cingulate cortex (ACC) during emotional interference, which in turn predicted shorter reaction times and might be related to stronger control of emotional interference. Conversely, Pro homozygotes exhibited increased orbitofrontal cortex (OFC) activation during emotional interference, with no behavioral advantage. Immunohistochemistry revealed AKAP5 expression in post mortem human ACC and OFC. Our results suggest that AKAP5 Pro100Leu contributes to individual differences in human aggression and anger control. Further research is warranted to explore the detailed role of AKAP5 and its gene product in human emotion processing.
doi:10.3389/fnhum.2011.00175
PMCID: PMC3247758  PMID: 22232585
AKAP5; genetic; aggression; anger; fMRI
9.  Oscillatory Brain Activity Related to Control Mechanisms during Laboratory-Induced Reactive Aggression 
Aggressive behavior is a common reaction in humans after an interpersonal provocation, but little is known about the underlying brain mechanisms. The present study analyzed oscillatory brain activity while participants were involved in an aggressive interaction to examine the neural processes subserving the associated decision and evaluation processes. Participants were selected from a larger sample because of their high scores in trait aggressiveness. We used a competitive reaction time task that induces aggressive behavior through provocation. Each trial is separated in a decision phase, during which the punishment for the opponent is set, and an outcome phase, during which the actual punishment is applied or received. We observed provocation-related differences during the decision phase in the theta band which differed depending on participants’ aggressive behavior: high provocation was associated with an increased frontal theta response in participants refraining from retaliation, but with reduced theta power in those who got back to the opponent. Moreover, more aggressive decisions after being punished were associated with a decrease of frontal theta power. Non-aggressive and aggressive participants differed also in their outcome-related response: being punished led to an increased frontal theta power compared to win trials in the latter only, pointing to differences in evaluation processes associated with their different behavioral reactions. The data thus support previous evidence for a role of prefrontal areas in the control of reactive aggression and extend behavioral studies on associations between aggression or violence and impaired prefrontal functions.
doi:10.3389/neuro.08.046.2009
PMCID: PMC2783022  PMID: 19949454
reactive aggression; electroencephalography; wavelet analysis; theta; beta
10.  Dopamine Agonist Increases Risk Taking but Blunts Reward-Related Brain Activity 
PLoS ONE  2008;3(6):e2479.
The use of D2/D3 dopaminergic agonists in Parkinson's disease (PD) may lead to pathological gambling. In a placebo-controlled double-blind study in healthy volunteers, we observed riskier choices in a lottery task after administration of the D3 receptor-preferring agonist pramipexole thus mimicking risk-taking behavior in PD. Moreover, we demonstrate decreased activation in the rostral basal ganglia and midbrain, key structures of the reward system, following unexpected high gains and therefore propose that pathological gambling in PD results from the need to seek higher rewards to overcome the blunted response in this system.
doi:10.1371/journal.pone.0002479
PMCID: PMC2423613  PMID: 18575579

Results 1-10 (10)