Individual differences in reward responding explain placebo-induced expectations and effects.
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.
Scott
David J
DJ
Department of Psychiatry and Molecular and Behavioral Neuroscience Institute, The University of Michigan, Ann Arbor, MI 48109-0720, USA.
Stohler
Christian S
CS
Egnatuk
Christine M
CM
Wang
Heng
H
Koeppe
Robert A
RA
Zubieta
Jon-Kar
JK
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
D004298:Dopamine