1 Goetz, C.G. et al. Placebo influences on dyskinesia in Parkinson's disease. Mov. Disord. 23, 700–707 (2008).

2 Goetz, C.G. et al. Placebo response in Parkinson's disease: comparisons among 11 trials covering medical and surgical interventions. Mov. Disord. 23, 690–699 (2008).

3 McRae, C. et al. Effects of perceived treatment on quality of life and medical outcomes in a double-blind placebo surgery trial. Arch. Gen. Psychiatry 61, 412–420 (2004).

4 Benedetti, F. et al. Placebo-responsive Parkinson patients show decreased activity in single neurons of subthalamic nucleus. Nat. Neurosci. 7, 587–588 (2004).

5 de la Fuente-Fernández, R. et al. Expectation and dopamine release: mechanism of the placebo effect in Parkinson's disease. Science 293, 1164–1166 (2001).

6 Lidstone, S.C. et al. Effects of expectation on placebo-induced dopamine release in Parkinson disease. Arch. Gen. Psychiatry 67, 857–865 (2010).

7 Voon, V. et al. Mechanisms underlying dopamine-mediated reward bias in compulsive behaviors. Neuron 65, 135–142 (2010).

8 de la Fuente-Fernández, R. et al. Dopamine release in human ventral striatum and expectation of reward. Behav. Brain Res. 136, 359–363 (2002).

9 Schweinhardt, P., Seminowicz, D.A., Jaeger, E., Duncan, G.H. & Bushnell, M.C. The anatomy of the mesolimbic reward system: a link between personality and the placebo analgesic response. J. Neurosci. 29, 4882–4887 (2009).

10 Zubieta, J.K. & Stohler, C.S. Neurobiological mechanisms of placebo responses. Ann. NY Acad. Sci. 1156, 198–210 (2009).

11 Pessiglione, M., Seymour, B., Flandin, G., Dolan, R.J. & Frith, C.D. Dopamine-dependent prediction errors underpin reward-seeking behavior in humans. Nature 442, 1042–1045 (2006).

12 Sutton, R.S. & Barto, A.G. Reinforcement Learning: an Introduction (Bradford Book, 1998).

13 Barto, A.G. Reinforcement learning and dynamic programming. in Analysis, Design and Evaluation of Man-Machine Systems, Vol. 1,2 (ed. Johannsen, G.) 407–412 (1995).

14 Daw, N.D. in Trial-by-trial data analysis using computational models. Decision Making, Affect, Learning: Attention and Performance XXIII, Vol. 1 (eds. Delgado, M.R., Phelps, E.A. & Robbins, T.W.) 3–38 (Oxford University Press, 2011).

15 Daw, N.D., O'Doherty, J.P., Dayan, P., Seymour, B. & Dolan, R.J. Cortical substrates for exploratory decisions in humans. Nature 441, 876–879 (2006).

16 Hare, T.A., O'Doherty, J., Camerer, C.F., Schultz, W. & Rangel, A. Dissociating the role of the orbitofrontal cortex and the striatum in the computation of goal values and prediction errors. J. Neurosci. 28, 5623–5630 (2008).

17 Levy, D.J. & Glimcher, P.W. The root of all value: a neural common currency for choice. Curr. Opin. Neurobiol. 22, 1027–1038 (2012).

18 Plassmann, H., O'Doherty, J.P. & Rangel, A. Appetitive and aversive goal values are encoded in the medial orbitofrontal cortex at the time of decision making. J. Neurosci. 30, 10799–10808 (2010).

19 McClure, S.M., Berns, G.S. & Montague, P.R. Temporal prediction errors in a passive learning task activate human striatum. Neuron 38, 339–346 (2003).

20 O'Doherty, J.P., Dayan, P., Friston, K., Critchley, H. & Dolan, R.J. Temporal difference models and reward-related learning in the human brain. Neuron 38, 329–337 (2003).

21 Daw, N.D. & Doya, K. The computational neurobiology of learning and reward. Curr. Opin. Neurobiol. 16, 199–204 (2006).

22 Rushworth, M.F., Mars, R.B. & Summerfield, C. General mechanisms for decision making. Curr. Opin. Neurobiol. 19, 75–83 (2009).

23 Chowdhury, R. et al. Dopamine restores reward prediction errors in old age. Nat. Neurosci. 16, 648–653 (2013).

24 Schönberg, T., Daw, N.D., Joel, D. & O'Doherty, J.P. Reinforcement learning signals in the human striatum distinguish learners from nonlearners during reward-based decision making. J. Neurosci. 27, 12860–12867 (2007).

25 Schönberg, T. et al. Selective impairment of prediction error signaling in human dorsolateral but not ventral striatum in Parkinson's disease patients: evidence from a model-based fMRI study. Neuroimage 49, 772–781 (2010).

26 Behrens, T.E., Hunt, L.T., Woolrich, M.W. & Rushworth, M.F. Associative learning of social value. Nature 456, 245–249 (2008).

27 Li, J., Delgado, M.R. & Phelps, E.A. How instructed knowledge modulates the neural systems of reward learning. Proc. Natl. Acad. Sci. USA 108, 55–60 (2011).

28 Niv, Y., Edlund, J.A., Dayan, P. & O'Doherty, J.P. Neural prediction errors reveal a risk-sensitive reinforcement-learning process in the human brain. J. Neurosci. 32, 551–562 (2012).

29 Kirsch, I. Response expectancy as a determinant of experience and behavior. Am. Psychol. 40, 1189–1202 (1985).

30 Wager, T.D. et al. Placebo-induced changes in FMRI in the anticipation and experience of pain. Science 303, 1162–1167 (2004).

31 Pessiglione, M. et al. Subliminal instrumental conditioning demonstrated in the human brain. Neuron 59, 561–567 (2008).

32 Schmidt, L., Palminteri, S., Lafargue, G. & Pessiglione, M. Splitting motivation: unilateral effects of subliminal incentives. Psychol. Sci. 21, 977–983 (2010).

33 Benedetti, F. How the doctor's words affect the patient's brain. Eval. Health Prof. 25, 369–386 (2002).

34 Fournier, J.C. et al. Antidepressant drug effects and depression severity: a patient-level meta-analysis. J. Am. Med. Assoc. 303, 47–53 (2010).

35 Kirsch, I. & Sapirstein, G. Listening to Prozac but hearing placebo: a meta-analysis of antidepressant medication. Prev. Treat. 1, 2a (1998).

36 Bódi, N. et al. Reward-learning and the novelty-seeking personality: a between- and within-subjects study of the effects of dopamine agonists on young Parkinson's patients. Brain 132, 2385–2395 (2009).

37 Frank, M.J., Seeberger, L.C. & O'Reilly, R.C. By carrot or by stick: cognitive reinforcement learning in parkinsonism. Science 306, 1940–1943 (2004).

38 Palminteri, S. et al. Pharmacological modulation of subliminal learning in Parkinson's and Tourette's syndromes. Proc. Natl. Acad. Sci. USA 106, 19179–19184 (2009).

39 Maia, T.V. Reinforcement learning, conditioning, and the brain: successes and challenges. Cogn. Affect. Behav. Neurosci. 9, 343–364 (2009).

40 Gold, J.M. et al. Negative symptoms and the failure to represent the expected reward value of actions: behavioral and computational modeling evidence. Arch. Gen. Psychiatry 69, 129–138 (2012).

41 Bamford, N.S. et al. Heterosynaptic dopamine neurotransmission selects sets of corticostriatal terminals. Neuron 42, 653–663 (2004).

42 Wang, W. et al. Regulation of prefrontal excitatory neurotransmission by dopamine in the nucleus accumbens core. J. Physiol. (Lond.) 590, 3743–3769 (2012).

43 Bamford, N.S. et al. Dopamine modulates release from corticostriatal terminals. J. Neurosci. 24, 9541–9552 (2004).

44 Colloca, L. et al. Learning potentiates neurophysiological and behavioral placebo analgesic responses. Pain 139, 306–314 (2008).

45 Voudouris, N.J., Peck, C.L. & Coleman, G. The role of conditioning and verbal expectancy in the placebo response. Pain 43, 121–128 (1990).

46 Kordower, J.H. et al. Disease duration and the integrity of the nigrostriatal system in disease. Brain 136, 2419–2431 (2013).

47 Cools, R., Barker, R.A., Sahakian, B.J. & Robbins, T.W. Enhanced or impaired cognitive function in Parkinson's disease as a function of dopaminergic medication and task demands. Cereb. Cortex 11, 1136–1143 (2001).

48 Frank, M.J., Seeberger, L.C. & O'Reilly, R.C. By carrot or by stick: cognitive reinforcement learning in parkinsonism. Science 306, 1940–1943 (2004).

49 Shohamy, D., Myers, C.E., Geghman, K.D., Sage, J. & Gluck, M.A. L-dopa impairs learning, but spares generalization, in Parkinson's disease. Neuropsychologia 44, 774–784 (2006).

50 Shohamy, D., Myers, C.E., Grossman, S., Sage, J. & Gluck, M.A. The role of dopamine in cognitive sequence learning: evidence from Parkinson's disease. Behav. Brain Res. 156, 191–199 (2005).

51 Benedetti, F. et al. Placebo-responsive Parkinson patients show decreased activity in single neurons of subthalamic nucleus. Nat. Neurosci. 7, 587–588 (2004).

52 Benedetti, F. et al. Electrophysiological properties of thalamic, subthalamic and nigral neurons during the anti-parkinsonian placebo response. J. Physiol. (Lond.) 587, 3869–3883 (2009).

53 Starkstein, S.E. et al. Reliability, validity, and clinical correlates of apathy in Parkinson's disease. J. Neuropsychiatry Clin. Neurosci. 4, 134–139 (1992).

54 Spielberger, C.D. State-Trait Anxiety Inventory: Bibliography, 2nd edn. (Consulting Psychologists Press, 1989).

55 Movement Disorder Society Task Force on Rating Scales for Parkinson's Disease. The Unified Parkinson's Disease Rating Scale (UPDRS): status and recommendations. Mov. Disord. 18, 738–750 (2003).

56 Sutton, R.S. & Barto, A.G. Reinforcement Learning: an Introduction (Bradford Book, 1998).

57 Lindquist, M.A., Spicer, J., Asllani, I. & Wager, T.D. Estimating and testing variance components in a multi-level GLM. Neuroimage 59, 490–501 (2012).

58 Mazaika, P., Hoeft, F., Glover, G.H. & Reiss, A.L. Methods and software for fMRI analysis of clinical subjects. Organ. Hum. Brain Mapp 475 (2009).

59 Hare, T.A., O'Doherty, J., Camerer, C.F., Schultz, W. & Rangel, A. Dissociating the role of the orbitofrontal cortex and the striatum in the computation of goal values and prediction errors. J. Neurosci. 28, 5623–5630 (2008).

60 Pessiglione, M., Seymour, B., Flandin, G., Dolan, R.J. & Frith, C.D. Dopamine-dependent prediction errors underpin reward-seeking behavior in humans. Nature 442, 1042–1045 (2006).

61 Behrens, T.E., Hunt, L.T., Woolrich, M.W. & Rushworth, M.F. Associative learning of social value. Nature 456, 245–249 (2008).

62 Niv, Y., Edlund, J.A., Dayan, P. & O'Doherty, J.P. Neural prediction errors reveal a risk-sensitive reinforcement-learning process in the human brain. J. Neurosci. 32, 551–562 (2012).

63 Li, J., Delgado, M.R. & Phelps, E.A. How instructed knowledge modulates the neural systems of reward learning. Proc. Natl. Acad. Sci. USA 108, 55–60 (2011).