title: Individual differences in reward responding explain placebo-induced expectations and effects.
abstract: Expectations, positive or negative, are modulating factors influencing behavior. They are also thought to underlie placebo effects, impacting perceptions and biological processes. Using healthy human subjects, we examined the role of the nucleus accumbens (NAC), a region centrally involved in the encoding of reward expectation, in the formation of placebo responses. Employing functional molecular imaging, activation of NAC dopamine (DA) release was observed during placebo administration and related to its anticipated effects, perception-anticipation mismatches, and placebo effect development. In additional functional MRI studies, the expectation of monetary gain increased NAC synaptic activity in a manner proportional to placebo-induced DA release, anticipated effects, perception-anticipation differentials, and actual placebo effects. Individual variations in NAC response to reward expectation accounted for 28% of the variance in the formation of placebo analgesia.
authors.affiliation: Department of Psychiatry and Molecular and Behavioral Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-0720, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Scott
authors.forename: Christian S
authors.initials: CS
authors.lastname: Stohler
authors.forename: Christine M
authors.initials: CM
authors.lastname: Egnatuk
authors.forename: Heng
authors.initials: H
authors.lastname: Wang
authors.forename: Robert A
authors.initials: RA
authors.lastname: Koeppe
authors.forename: Jon-Kar
authors.initials: JK
authors.lastname: Zubieta
mesh_terms: D000328:Adult; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D005717:Games, Experimental; D006801:Humans; D007206:Individuality; D008279:Magnetic Resonance Imaging; D008297:Male; D009714:Nucleus Accumbens / Q000378:metabolism / Q000502:physiology*; D010146:Pain / Q000378:metabolism / Q000523:psychology; D015990:Placebo Effect; D049268:Positron-Emission Tomography; D012016:Reference Values; D012201:Reward; D012718:Set, Psychology
chemical_list: D004298:Dopamine