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Dopamine is known as the main neurotransmitter modulating the activation of the reward system of the brain. The DRD2 TaqIA polymorphism is associated with dopamine D2 receptor density which plays an important role in the context of reward. Persons carrying an A1 allele have a lower D2 receptor density and a higher risk to show substance abuse. The present study was designed to investigate the influence of the DRD2 TaqIA polymorphism and the selective D2 receptor agonist bromociptine on the activation of the reward system by means of functional magnetic resonance imaging (fMRI). In a double-blind crossover study with 24 participants we found an increase of reward system activation from placebo to bromocriptine only in subjects carrying the A1 allele. Furthermore, only A1 carrier showed an increase of performance under bromocriptine. The results are interpreted as reflecting a specific sensitivity for dopamine agonists in persons carrying an A1 allele and may complement actual data and theories of the development of addiction disorders postulating a higher genetic risk for substance abuse in carrier of the A1 allele.
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The majority of neuroimaging studies on affective processing have indicated that there are specific brain structures, which are selectively responsive to fear and disgust. Whereas the amygdala is assumed to be fear-related, the insular cortex is most likely involved in disgust processing. Since these findings are mainly a result of studies focusing exclusively either on fear, or on disgust, but rarely on both emotions together, the present experiment explored the neural effects of viewing disgusting and fear-inducing pictures in contrast to neutral pictures. This was done by means of functional magnetic resonance imaging (fMRI) with 19 subjects (nine males, ten females), who also gave affective ratings for the presented pictures. The fear and the disgust pictures were able to induce the target emotions and they received comparable valence and arousal ratings. The processing of both aversive picture types was associated with an increased brain activation in the occipital-temporal lobe, in the prefrontal cortex, and in the thalamus. The amygdala was significantly activated by disgusting, but not by fear-inducing, pictures. Thus, our data are in contrast with the idea of highly emotion-specific brain structures and rather suggest the existence of a common affective circuit.
Erkunden
Eintragsart
Sprache
- Englisch (2)
Thema
- Oxygen/blood
- Adolescent (1)
- Adult (2)
- Brain/blood supply/*drug effects/physiology (1)
- Brain/physiology (1)
- Bromocriptine/*pharmacology (1)
- Cross-Sectional Studies (1)
- Dopamine Agonists/*pharmacology (1)
- Double-Blind Method (1)
- Emotions/*physiology (1)
- Fear/*physiology (1)
- Feedback, Psychological/drug effects/physiology (1)
- Female (2)
- Hemodynamics/*physiology (1)
- Humans (2)
- Image Processing, Computer-Assisted (1)
- Image Processing, Computer-Assisted/methods (1)
- Magnetic Resonance Imaging (1)
- Magnetic Resonance Imaging/methods (1)
- Male (2)
- Photic Stimulation (1)
- *Polymorphism, Genetic (1)
- Reaction Time/drug effects/genetics (1)
- Receptors, Dopamine D2/*genetics (1)
- Reverse Transcriptase Polymerase Chain Reaction/methods (1)
- *Reward (1)
- Sex Characteristics (1)