PET

Aarts, E, Wallace DL, Dang LC, Jagust WJ, Cools R, D'Esposito M.  2014.  Dopamine and the Cognitive Downside of a Promised Bonus., 2014 Feb 13. Psychological science. Abstract

It is often assumed that the promise of a monetary bonus improves cognitive control. We show that in fact appetitive motivation can also impair cognitive control, depending on baseline levels of dopamine-synthesis capacity in the striatum. These data not only demonstrate that appetitive motivation can have paradoxical detrimental effects for cognitive control but also provide a mechanistic account of these effects.

Cools, R, Gibbs SE, Miyakawa A, Jagust W, D’Esposito.  2008.  Working memory capacity predicts dopamine synthesis capacity in the human striatum., 2008 Jan 30. The Journal of neuroscience : the official journal of the Society for Neuroscience. 28:1208-12. Abstract2008_cools_j_neuro.pdf

Evidence from psychopharmacological research has revealed that dopamine receptor agents have opposite effects on cognitive function depending on baseline levels of working memory capacity. These contrasting effects have been interpreted to reflect differential baseline levels of dopamine. Here we demonstrate for the first time that working memory capacity as measured by listening span predicts dopamine synthesis capacity in the striatum, indicating that subjects with low working memory capacity have low DA synthesis capacity in the striatum, whereas subjects with high working memory capacity have high DA synthesis capacity in the striatum.

Cools, R, Frank MJ, Gibbs SE, Miyakawa A, Jagust W, D’Esposito.  2009.  Striatal dopamine predicts outcome-specific reversal learning and its sensitivity to dopaminergic drug administration., 2009 Feb 4. The Journal of neuroscience : the official journal of the Society for Neuroscience. 29:1538-43. Abstract2009cools.pdf

Individual variability in reward-based learning has been ascribed to quantitative variation in baseline levels of striatal dopamine. However, direct evidence for this pervasive hypothesis has hitherto been unavailable. We demonstrate that individual differences in reward-based reversal learning reflect variation in baseline striatal dopamine synthesis capacity, as measured with neurochemical positron emission tomography. Subjects with high baseline dopamine synthesis in the striatum showed relatively better reversal learning from unexpected rewards than from unexpected punishments, whereas subjects with low baseline dopamine synthesis in the striatum showed the reverse pattern. In addition, baseline dopamine synthesis predicted the direction of dopaminergic drug effects. The D(2) receptor agonist bromocriptine improved reward-based relative to punishment-based reversal learning in subjects with low baseline dopamine synthesis capacity, while impairing it in subjects with high baseline dopamine synthesis capacity in the striatum. Finally, this pattern of drug effects was outcome-specific, and driven primarily by drug effects on punishment-, but not reward-based reversal learning. These data demonstrate that the effects of D(2) receptor stimulation on reversal learning in humans depend on task demands and baseline striatal dopamine synthesis capacity.