Table 1:

Characteristics of studies included in the meta-analysis

Study	Sample	Condition	Stimulation	Method of stimulation	Sex (M,F)	N	Age	Type	Significance
Opioid
Carfentanil
Prossin, 2015	Healthy controls	Pain Increase	Masseter muscle pain	Hypertonic Saline	12, 22	34	22±11	WBA	p<0.001
Zubieta, 2001	Healthy controls	Pain Increase	Masseter muscle pain	Hypertonic Saline	13,7	20	24±2	WB	p<0.05
Scott, 2007	Healthy controls	Pain Increase	Masseter muscle pain	Hypertonic Saline	14,0	15	27±5	WBA & ROI	p < 0.01
Wager, 2007	Healthy controls	Pain Increase	Thermal Pain	Thermode	n/a	15	25±5	ROI	p < 0.001
Scott, 2008	Healthy controls	Pain Increase	Masseter muscle pain	Hypertonic Saline	9, 11	20	24±3	WBA	p < 0.0001
DaSilva, 2014	Migraine	Pain Increase	Headache pain	During headache	3,4	12	n/a	WBA	n/a
Nascimento, 2014	Migraine	Pain Increase	Thermal Pain	Thermode	3, 3	6	26	WBA	p < 0.0001
Pecina, 2015	Healthy controls	Pain Increase	Masseter muscle pain	Hypertonic Saline	21, 29	50	26±0.7	WBA	p < 0.0001
Zubieta, 2003	Healthy controls	Pain Increae	Sad mood induction	Autobiographical memory	0, 14	14	36±9	WBA	P < 0.001
Hsu, 2013	Healthy controls	Pain Increase	Rejection Pain	Social feedback task	5, 13	18	32±12	VOI	p < 0.05; p < 0.01
Harris, 2009	Fibromyalgia	Pain Releif	Fibromyalgia pain	Accupuncture	0, 20	20	44.3±13.6	WBA & ROI	P < 0.001
Pecina, 2013	Healthy controls	Pain Relief	Masseter muscle pain	Placebo	19, 18	37	30±10	WBA & ROI	p < 0.001; p < 0.05
Diprenorphine
Maarrawi, 2007	Neuropathic pain	Pain Increae	Chronic pain	Contralateral pain	4, 4	8	55.2±11	ROI	p < 0.0005
Wey, 2014	Healthy controls	Pain Increase	Pressure pain	Pressure cuff	4, 4	8	24	ROI	p < 0.05
Jones, 1999	Trigeminal Neralgia	Pain relief	Neuralgia pain	Surgery	6,0	6	61.5 ± 19.5	ROI	p < 0.01
Dopamine
Radopride
Berman, 2013	Writer’s cramp	Pain Increae	Writer’s cramp pain	Tapping Task	10, 5	15	52.41 ± 9	WBA & ROI	p < 0.05
Martikainen, 2015	CNBP patients	Pain Increae	Masseter muscle pain	Hypertonc saline	18, 14	16	35 ± 11	WBA & ROI	p < 0.05; p < 0.005
Pecina, 2015	Healthy controls	Pain Increae	Masseter muscle pain	Hypertonc saline	21, 29	50	26±0.7	WBA	p<0.05; p < 0.0001
Scott, 2006	Healthy controls	Pain Increae	Masseter muscle pain	Hypertonc saline	18, 7	25	27±5	WBA	p<0.0001; p<0.01
Scott, 2007	Healthy controls	Pain Increae	Masseter muscle pain	Hypertonc saline	14, 0	14	27±5	ROI	P < 0.01
Scott, 2008	Healthy controls	Pain Increae	Masseter muscle pain	Hypertonc saline	9, 11	20	24±3	WBA & ROI	p = 0.05, p<0.0001
Wood, 2007	FM patients	Pain Increae	Tibialis muscle pain	Hypertonc saline	0, 22	11	n/a	ROI	p < 0.05
Fally pride
Jarcho, 2015	Healthy controls	Pain Increase	Thermal Pain	Thermode	0, 15	15	24±3.11	WBA	p = 0.001

FM = Fibromyalgia; WBA =Whole brain analysis; VOI = Volume of interest; ROI = Region of interest; CNBP = Chronic non-neuropathic back pain