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  • 2000-2004  (2)
  • 1990-1994  (2)
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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 18 (2003), S. 0 
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: This study investigated the processing of increasing monetary reward in nonsmoking and smoking subjects. The choice of the subject populations has been motivated by the observation of differences between nonsmokers and smokers in response to rewarding stimuli in a previous study. Subjects performed a pattern recognition task with delayed response, while rCBF was measured with [\mathrm{H}^{15}_{2}O] PET. Correct responses to the task were reinforced with three different amounts of monetary reward. The subjects received the sum of the rewards at the end of the experiment. The results show that a cortico-subcortical loop, including the dorsolateral prefrontal cortex, the orbitofrontal cortex, the cingulate gyrus and the thalamus is involved in processing increasing monetary reward. Furthermore, the striatal response differentiates nonsmokers from smokers. Thus, we found significant correlations between rCBF increases in striatum and increasing monetary reward and between striatal rCBF increases and mood in nonsmokers, but not in smokers. Moreover, no significant mood changes among the different monetary rewards could be observed in smokers. We infer that the response of the striatum to reward is related to changes in subjective feelings. The differences between smokers and nonsmokers confirm our previous conclusions that the association between blood flow, performance, mood and amount of reward is more direct in nonsmokers.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 14 (2001), S. 0 
    ISSN: 1460-9568
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Many studies indicate a role of the cerebral dopaminergic reward system in addiction. Motivated by these findings, we examined in opiate addicts whether brain regions involved in the reward circuitry also react to human prototypical rewards. We measured regional cerebral blood flow (rCBF) with H215O positron emission tomography (PET) during a visuo-spatial recognition task with delayed response in control subjects and in opiate addicts participating in a methadone program. Three conditions were defined by the types of feedback: nonsense feedback; nonmonetary reinforcement; or monetary reward, received by the subjects for a correct response. We found in the control subjects rCBF increases in regions associated with the meso-striatal and meso-corticolimbic circuits in response to both monetary reward and nonmonetary reinforcement. In opiate addicts, these regions were activated only in response to monetary reward. Furthermore, nonmonetary reinforcement elicited rCBF increases in limbic regions of the opiate addicts that were not activated in the control subjects. Because psychoactive drugs serve as rewards and directly affect regions of the dopaminergic system like the striatum, we conclude that the differences in rCBF increases between controls and addicts can be attributed to an adaptive consequence of the addiction process.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 17 (1990), S. 275-281 
    ISSN: 1434-6079
    Schlagwort(e): 36.10.—k ; 36.10.Dr
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Precise determination of the four coupling constants describing the parity-odd neutral current interaction between muon and nucleons would provide a critical test of the standard model. The directional correlation between the photon emitted in the transition between 2S- and 1S-states and the decay electron provides a suitable observable. The two isotopes of boron constitute a unique system for a complete determination of the coupling constants. Completeness requires that the hyperfine components of the initial or final state of the photon transition be distinguished. An elegant method of measuring the directional correlations in the hyperfine components of the final state is the Fourier analysis of the muon spin precession in correlation with the emitted photon radiation. The purpose of this paper is to derive the relationship between the directional correlations and the coupling constants, determine optimal energy and angular intervals for a measurement, and discuss the experimental issues which must be resolved in preparation of an experiment.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    ISSN: 1572-9540
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Negative muons of 28.6 Mev/c initial momentum were decelerated in and extracted from the PSI anticyclotron equipped with a Mylar foil in the median plane as moderator to provide a continuous μ− beam of 3–30 keV energy. This technique can also be used to post-decelerate LEAR antiprotons in a continuous or pulsed mode to keV energies with an efficiency up to 10–20%.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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