Het beloningssysteem in de hersenen: weten, meten en ingrijpen

04/2007; 11(2):38-42. DOI: 10.1007/BF03079122


Verslaving en depressie zijn aandoeningen waarbij het beloningssysteem is ontregeld en de motivatie en het levensgeluk ernstig
zijn aangetast. Twee vragen wil ik hier beantwoorden: heeft een wetenschappelijke benadering van motivatie en geluk wel bestaansrecht
en hoe zouden eventuele interventies moeten plaatsvinden?

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    ABSTRACT: The human amygdala's involvement in negative emotion is well established, but relatively little is known regarding its role in positive emotion. Here we examined the neural response to emotionally positive, negative, and neutral words using fMRI. Relative to neutral words, positive and negative emotional words elicited greater activity in the left amygdala. Positive but not negative words elicited activity in dorsal and ventral striatal regions which have been linked in previous neuroimaging studies to reward and positive affect, including caudate, putamen, globus pallidus, and accumbens. These findings provide the first direct evidence that the amygdala is involved in emotional reactions elicited by both positive and negative emotional words, and further indicate that positive words additionally activate brain regions related to reward.
    Neuroreport 02/2002; 13(1):15-9. DOI:10.1097/00001756-200201210-00008 · 1.52 Impact Factor
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    ABSTRACT: The human striatum is functionally organized into limbic, associative, and sensorimotor subdivisions, which process information related to emotional, cognitive, and motor function. Dopamine projections ascending from the midbrain provide important modulatory input to these striatal subregions. The aim of this study was to compare activation of dopamine D2 receptors after amphetamine administration in the functional subdivisions of the human striatum. D2 receptor availability (V3") was measured with positron emission tomography and [11C]raclopride in 14 healthy volunteers under control conditions and after the intravenous administration of amphetamine (0.3 mg/kg). For each condition, [11C]raclopride was administered as a priming bolus followed by constant infusion, and measurements of D2 receptor availability were obtained under sustained binding equilibrium conditions. Amphetamine induced a significantly larger reduction in D2 receptor availability (DeltaV3") in limbic (ventral striatum, -15.3 +/- 11.8%) and sensorimotor (postcommissural putamen, -16.1 +/- 9.6%) regions compared with associative regions (caudate and precommissural putamen, -8.1 +/- 7.2%). Results of this region-of-interest analysis were confirmed by a voxel-based analysis. Correction for the partial volume effect showed even greater differences in DeltaV3" between limbic (-17.8 +/- 13.8%), sensorimotor (-16.6 +/- 9.9%), and associative regions (-7.5 +/- 7.5%). The increase in euphoria reported by subjects after amphetamine was associated with larger DeltaV3" in the limbic and sensorimotor regions, but not in the associative regions. These results show significant differences in the dopamine response to amphetamine between the functional subdivisions of the human striatum. The mechanisms potentially accounting for these regional differences in amphetamine-induced dopamine release within the striatum remain to be elucidated, but may be related to the asymmetrical feed-forward influences mediating the integration of limbic, cognitive, and sensorimotor striatal function via dopamine cell territories in the ventral midbrain.
    Journal of Cerebral Blood Flow & Metabolism 04/2003; 23(3):285-300. DOI:10.1097/01.WCB.0000048520.34839.1A · 5.41 Impact Factor
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    ABSTRACT: Using intracerebral microdialysis in urethane-anaesthetized adult male Wistar rats, we monitored the effects of acute repetitive transcranial magnetic stimulation (rTMS; 20 trains of 20 Hz, 2.5 s) on the intrahypothalamic release of arginine vasopressin (AVP) and selected amino acids (glutamate, glutamine, aspartate, serine, arginine, taurine, γ-aminobutyric acid) and the intrahippocampal release of monoamines (dopamine, noradrenaline, serotonin) and their metabolites (homovanillic acid, 3,4-dihydroxyphenylacetic acid, 5-hydroxyindoleacetic acid). The stimulation parameters were adjusted according to the results of accurate computer reconstructions of the current density distributions induced by rTMS in the rat and human brains, ensuring similar stimulation patterns in both cases. There was a continuous reduction in AVP release of up to 50% within the hypothalamic paraventricular nucleus in response to rTMS. In contrast, the release of taurine, aspartate and serine was selectively stimulated within this nucleus by rTMS. Furthermore, in the dorsal hippocampus the extracellular concentration of dopamine was elevated in response to rTMS. Taken together, these data provide the first in vivo evidence that acute rTMS of frontal brain regions has a differentiated modulatory effect on selected neurotransmitter/neuromodulator systems in distinct brain areas.
    European Journal of Neuroscience 09/2000; 12(10):3713 - 3720. DOI:10.1046/j.1460-9568.2000.00243.x · 3.18 Impact Factor
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