Table 1.

Experiments included in the meta-analyses.

Study	Category	Imaging modality	Type of pain	Sample size	Contrasts associated with reduced activation	Contrasts associated with increased activation
(Petrovic et al. 2002)	Placebo analgesia	PET rCBF	Thermal	9	N/A	1. (Pain + Placebo)-(Pain alone); 2.[(Pain + Placebo)-(Pain alone)]-[(Warm + Placebo)-(Warm alone])
(Wager et al. 2004): Study 1	Placebo analgesia	fMRI	Shock	24	1. (Control-Placebo)-(Intense-Mild Shock)	N/A
(Wager et al. 2004): Study 2	Placebo analgesia	fMRI	Thermal	23	1. (Control-Placebo) during early pain; 2. (Control-Placebo) during late pain	1. (Placebo-Control) during anticipation
(Zubieta et al. 2005)	Placebo analgesia	PET μOR binding	Muscle (sustained)	14	N/A	1. (Placebo-Control) opioid increase; carfentanil binding decrease
(Koyama et al. 2005)	Stimulus expectancy	fMRI	Thermal	10	1. Decreased pain-induced activation evoked by decreased expectations (expect 48C,actual 50C versus expect 50C,actual 50C)	N/A
(Bingel et al. 2006)	Placebo analgesia	fMRI	Laser	19	N/A	1. (Placebo-Control) during laser stimulation
(Kong et al. 2006)	Placebo analgesia	fMRI	Thermal	24	N/A	1. (After-Before placebo treatment)-(Placebo-Control site)
(Keltner et al. 2006)	Stimulus expectancy	fMRI	Thermal	27	1. High Expectancy,High Temp-Low Expectancy,High temp	N/A
(Price et al. 2007)	Placebo analgesia	fMRI	Visceral (Rectal) in patients with irritable bowel syndrome	9	1. Pre-placebo (B1)-Placebo during pain AND Post-placebo (B2)-Placebo; ROIs	N/A
(Wager et al. 2007b)	Placebo analgesia	PET μOR binding	Thermal	15	N/A	1. (Placebo-Control) opioid increase,(Painful-Nonpainful Heat)
(Craggs et al. 2008)	Placebo analgesia	fMRI	Visceral (Rectal) in patients with irritable bowel syndrome	9	N/A	1. Placebo-Baseline during pain
(Eippert et al. 2009a)	Placebo analgesia	fMRI	Thermal	48	1. (Control-Placebo) during early pain; 2. (Control-Placebo) during late pain	1. (Placebo-Control) early pain; 2. (Placebo-Control) during pain,brainstem-specific
(Lu et al. 2009)	Placebo analgesia	fMRI	Visceral (Esophageal)	14	1. (Control-Placebo) during pain	N/A
(Watson et al. 2009)	Placebo analgesia	fMRI	Laser	11	N/A	1. (Placebo-Control) during anticipation
(Kong et al. 2009b)	Placebo analgesia	fMRI	Thermal	12	1. Control > High expectancy in Placebo group	1. Placebo acupuncture group (N=12),(Pre-Post-placebo) x (Placebo-Control) site
(Kong et al. 2009a)	Expectancy effects during treatment	fMRI	Thermal	Different size for each contrast	1. Verum acupuncture (High-Low expectancy) groups,(Pre-Post-treatment) n = 24; 2. ME of expectancy on high-expectancy site,(pre-post treatment) n = 48	1. Verum acup high-expectancy group,(Pre-Post-treatment)-(Expected-Control site) n = 12
(Harris et al. 2009)	Placebo analgesia	PET μOR binding	Chronic (fibromyalgia)	10	N/A	1. Opioid increase (binding decrease) After-Before sham acupuncture
(Lui et al. 2010)	Placebo analgesia	fMRI	Laser	31	N/A	1. Placebo/Low exp vs Control/High exp during anticipation; 2. Placebo/Low exp vs Control/High exp during pain
(Atlas et al. 2010)	Stimulus expectancy	fMRI	Thermal	18	1. Assimilation/Expectancy-induced reductions	1. Contrast/Expectancy-induced incr
(Wiech et al. 2010)	Stimulus expectancy	fMRI	Laser	16	1. High > Low threat,across pain and non; 2. Intxn: [Pain,High > Low threat] > [No pain,High > Low threat]	1. Low > High threat,across pain and non
(Bingel et al. 2011)	Expectancy effects during treatment	fMRI	Thermal	22	1. Placebo-Nocebo: Decreases	1. Placebo-Nocebo: Increases
(Lee et al. 2012)	Placebo analgesia	fMRI	Visceral (Rectal) in patients with irritable bowel syndrome and healthy controls	17	1. Placebo-control during rectal pain: healthy volunteers (decreases); 2. Placebo-control during rectal pain: IBS pts (decreases)	1. Placebo-control during rectal pain: healthy volunteers (increases); 2. Placebo-control during rectal pain: IBS pts (increases)
(Geuter et al. 2012)	Placebo analgesia	fMRI	Thermal	40	1. antic: (Control > strong placebo) > (Control > Weak placebo); 2. Early pain: Control > placebo; 3. Late pain: Control > placebo; 4. Late pain: Control > strong placebo; 5. Late pain: Control > weak placebo; 6. Late pain: (Control > strong placebo) > (Control > weak placebo)	1. antic: Placebo > Control; 2. antic: Strong placebo > Control; 3. antic: Weak placebo > Control; 4. Early pain: placebo > control; 5. Early pain: strong placebo > control; 6. Early pain: weak placebo > control; 7. Early pain: (Strong placebo > control) > (weak placebo > control); 8. Late pain: Weak placebo > control; 9. Late pain: (Strong placebo > Control) > (weak placebo > control)
(Atlas et al. 2012)	Expectancy effects during treatment	fMRI	Thermal	21	1. Instruction-related decreases; 2. Open-Hidden: Decreases	1. Instruction-related increases; 2. Open-Hidden: Increases
(Kong et al. 2013)	Stimulus expectancy	fMRI	Thermal	46	1. For subjs with large exp fx, HC > LC	1. Low cue > High cue, pain; 2. Low cue > High cue,antic