Table 1.
List of studies included in the ALE meta-analyses
| Study name | Type of subject, gender, mean age | Subliminal condition | Supraliminal condition | n | Foci | fMRI analysis | Activation threshold |
|---|---|---|---|---|---|---|---|
| a) Subliminal activation greater than supraliminal activation | |||||||
| Diekhof et al. 2009 | Healthy: 4 male, 5 female, 24.4 years (S.D. 2.2) | Subtle changes in audio frequency | Detectable changes in audio frequency | 9 | 1 | WBe | p < 0.001 |
| Lawal et al. 2006 | Irritable Bowel Syndrome: 10 female, Healthy: 10 female. 19–38 years | Rectal stimulation (bag inflated below perception threshold) | Rectal stimulation (bag inflated above perception threshold) | 18 | 17 | WBb | p < 0.05 |
| Phillips et al. 2004 | Healthy: 5 males (grp.1), 29.5 years (S.D. 4.7) 5 male (grp. 2) 28.4 years (S.D. 6.2) | Covert angry and disgusted faces | Overt angry and disgusted faces | 8 | 23 | WBb | p < 0.005 |
| Prochnow et al. 2013 | Healthy: 5 men, 7 women, 23.8 years (S.D. 3.0) | Covert facial expressions of happiness, anger, sadness | Overt facial expressions of happiness, anger, sadness | 12 | 11 | WBe | p < 0.05 (2 foci at p < 0.01) |
| Sidhu et al. 2004 | Irritable Bowel Syndrome: 8 female, Healthy: 8 female, 19–38 years | Rectal stimulation (bag inflated below perception) | Rectal stimulation (bag inflated at perception and above perception) | 16 | 64 | WBb | p < 0.05 |
| Only subliminal stimulation | |||||||
| Duan et al. 2010 | Healthy: 5 males, 13 females, 23.6 years (S.D. 1.3) | Covert surprised faces | 18 | 41 | WBb | p < 0.001 | |
| Kouider et al. 2009 | Healthy: 8 males, 8 female, 23 years (S.D. 2) | Covert famous faces | 16 | 9 | WBe | p < 0.001 | |
| Smith et al. 2011 | Healthy female, 29 years (range 19–53) | Rectal stimulation (bag inflated below perception) | 14 | 13 | WBb | p < 0.001 | |
| Song et al. 2006 | Irritable Bowel Syndrome: 12 female, Healthy: 12 female. 23 years (S.D. 0.3/S.D. 0.92) | Rectal stimulation (bag inflated below perception) | 24 | 13 | WBb | p < 0.001 | |
| 135 | 192 | ||||||
| b) Supraliminal activation greater than subliminal activation | |||||||
| Diekhof et al. 2009 | Healthy: 4 male, 5 female, 24.4 years (S.D. 2.2) | Subtle changes in audio frequency | Changes in audio frequency | 9 | 27 | WBe | p < 0.001 |
| Gillath & Canterberry, 2011 | Healthy: 19 male. 20 female, 19.65 years (no avail S.D.) | Masked sexual images presented at 23 ms | Supraliminal masked sexual images presented at 524 ms | 39 | 21 | WBe | p < 0.001 |
| Lawal et al. 2006 | Irritable Bowel Syndrome: 10 female, Healthy: 10 female. 19–38 years | Rectal stimulation (bag inflated below perception threshold) | Rectal stimulation (bag inflated above perception threshold) | 18 | 25 | WBb | p < 0.05 |
| Phillips et al. 2004 | Healthy: 5 male (grp.1), 29.5 years (S.D. 4.7) 5 male (grp. 2) 28.4 years (S.D. 6.2) | Covert angry and disgusted faces | Overt angry and disgusted faces | 8 | 32 | WBb | p < 0.005 |
| Prochnow et al. 2013 | Healthy: 5 men, 7 women, 23.8 years (S.D. 3.0) | Covert facial expressions of happiness, anger, sadness | Overt facial expressions of happiness, anger, sadness | 12 | 11 | WBe | p < 0.05 (2 foci at p < 0.01) |
| Sidhu et al. 2004 | Irritable Bowel Syndrome: 8 female, Healthy: 8 female, 19–38 years | Rectal stimulation (bag inflated below perception) | Rectal stimulation (bag inflated at perception and above perception) | 16 | 136 | WBb | p < 0.05 |
| Only supraliminal stimulation | |||||||
| Hall et al. 2010 | Irritable Bowel Syndrome: 7 female, Healthy: 6 female, 30–40 years | Rectal stimulation (bag inflated above pain perception) | 13 | 26 | WBe | p < 0.001 | |
| Kouider et al. 2009 | Healthy: 8 males, 8 female, 23 years (S.D. 2) | Overt famous faces | 16 | 8 | WBe | p < 0.001 | |
| Smith et al. 2011 | Healthy female, 29 years (range 19–53) | Rectal stimulation (bag inflated above pain perception) | 14 | 9 | WBb | p < 0.001 | |
| Song et al. 2006 | Irritable Bowel Syndrome: 12 female, Healthy: 12 female. 23 years (S.D. 0.3/S.D. 0.92) | Rectal stimulation (bag inflated above pain perception) | 24 | 20 | WBb | p < 0.001 | |
| 169 | 315 | ||||||
| Grand Total: | 304 | 507 | |||||
bBlock design fMRI, eEvent-related fMRI, n = number of participants, foci = number of separate Talairach coordinates contributing to the meta-analysis, n = number of participants, WB = Whole Brain Analysis, S.D. = Standard deviation. Note: all participants had no psychiatric comorbidities.