Meta-analytic methods for fMRI, VBM and PET
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Introduction

Signed Differential Mapping is a statistical technique for meta-analyzing studies on differences in brain activity or structure which used neuroimaging techniques such as fMRI, VBM or PET. Meta-analyses using this method have been already published at high quality journals such as Arch Gen Psychiat / JAMA Psychiatry , Am J Psychiatry , Neurosci Biobehav Rev , Biol Psychiat , Schizophrenia Bull , Br J Psychiat , Neurobiol Aging , Curr Opin Neurobiol , Neuroimage , Hum Brain Mapp , Psychol Med , Schizophr Res , Curr Med Chem , Neuropsychologia , J Psychiatry Neurosci , J Clin Psychopharmacol , PLoS One , J Psychiatr Res , Acta Psychiatr Scand , J Affect Disorders , Eur J Neurol , Dement Geriatr Cogn Disord , Eur Psychiat , Amyotroph Lateral Sc , World J Biol Psychia , Psychiatry Res , Neurol Sci , Biol Mood Anxiety Disord or Asian J Psychiatr .

The method

An introduction of the method can be found in the SDM Reference Manual.

Briefly, some of the features are:

• Possibility of combining group peak coordinates with parametric images.
• A criterion in the selection of the coordinates to avoid biases towards liberally thresholded regions.
• Use of specific gray or white matter templates.
• Accounting for different sources of spatial error (e.g. coregistration mismatch or the size of the cluster), peaks' effect-size, and signed maps to counteract positive and negative differences.
• Weights in the calculations: intra-study variance (i.e. studies with large sample sizes and/or lower error contribute more) and other optional weights.
• Use of the general linear model and inter-study heterogeneity to allow meta-analytical comparisons between groups and use of covariates.
• Complementary analyses such as exploration of heterogeneity (by means of heterogeneity maps, subgroup analyses and meta-regressions) and jackknife analyses (to assess the replicability of the results).

The software

Please feel free to download the software created by the SDM Project to carry out such meta-analyses.

References

Papers introducing relevant SDM methods:

1. Introduction to voxel-based meta-analyses: Radua J and Mataix-Cols D. Meta-analytic methods for neuroimaging data explained. Biol Mood Anxiety Disord 2012; 2:6.
2. SDM method 1/3 (original algorithms): Radua J and Mataix-Cols D. Voxel-wise meta-analysis of grey matter changes in obsessive-compulsive disorder. Br J Psychiatry 2009; 195:393-402.
3. SDM method 2/3 (comparisons and linear models): Radua J, van den Heuvel OA, Surguladze S and Mataix-Cols D. Meta-analytical comparison of voxel-based morphometry studies in obsessive compulsive disorder vs other anxiety disorders. Arch Gen Psychiatry 2010; 67:701-711.
4. SDM method 3/3 (effect-sizes and variances): Radua J, Mataix-Cols D, Phillips ML, El-Hage W, Kronhaus DM, Cardoner N and Surguladze S. A new meta-analytic method for neuroimaging studies that combines reported peak coordinates and statistical parametric maps. Eur Psychiatry 2012; 27:605–611.
5. SDM specific white matter template: Radua J, Via E, Catani M and Mataix-Cols D. Voxel-based meta-analysis of regional white-matter volume differences in autism spectrum disorder versus healthy controls. Psychol Med 2011; 41:1539-1550.
6. SDM specific TBSS preprocessing and template: Peters BD, Szeszko PR, Radua J, Ikuta T, Gruner P, DeRosse P, Zhang JP, Giorgio A, Qiu D, Tapert SF, Brauer J, Asato MR, Khong PL, James AC, Gallego JA and Malhotra AK. White matter development in adolescence: diffusion tensor imaging and meta-analytic results. Schizophrenia Bull 2012; 38:1308-1317.
7. Multimodal meta-analyses (theory): Radua J, Romeo M, Mataix-Cols D and Fusar-Poli P. A general approach for combining voxel-based meta-analyses conducted in different neuroimaging modalities. Curr Med Chem 2013; 20:462-466.
8. Multimodal meta-analyses (example): Radua J, Borgwardt S, Crescini A, Mataix-Cols D, Meyer-Lindenberg A, McGuire PK and Fusar-Poli P. Multimodal meta-analysis of structural and functional brain changes in first episode psychosis and the effects of antipsychotic medication. Neurosci Biobehav Rev 2012; 36:2325–2333.

Other studies using SDM:

9. Bora E, Fornito A, Yücel M and Pantelis C. Voxelwise meta-analysis of gray matter abnormalities in bipolar disorder. Biol Psychiatry 2010; 67:1097-1105.
10. Chen Z and Ma L. Grey matter volume changes over the whole brain in amyotrophic lateral sclerosis: A voxel-wise meta-analysis of voxel based morphometry studies. Amyotroph Lateral Scler 2010; 11:549-554.
11. Bora E, Fornito A, Radua J, Walterfang M, Seal M, Wood SJ, Yücel M, Velakoulis D and Pantelis C. Neuroanatomical abnormalities in schizophrenia: A multimodal voxelwise meta-analysis and meta-regression analysis. Schizophr Res 2011; 127:46-57.
12. Richlan F, Kronbichler M and Wimmer H. Meta-analyzing brain dysfunctions in dyslexic children and adults. Neuroimage 2011; 56:1735-42.
13. E Via, J Radua, N Cardoner, F Happe and D Mataix-Cols. Meta-analysis of gray matter abnormalities in autism spectrum disorder: should Asperger disorder be subsumed under a broader umbrella of autistic spectrum disorder? Arch Gen Psychiatry 2011; 68:409-418.
14. Lai CH. Gray matter deficits in panic disorder: a pilot study of meta-analysis. J Clin Psychopharmacol 2011; 31:287-93.
15. Bora E, Fornito A, Pantelis C and Yücel M. Gray matter abnormalities in Major Depressive Disorder: A meta-analysis of voxel based morphometry studies. J Affect Disord 2012; 138:9-18.
16. Li J, Pan P, Song W, Huang R, Chen K and Shang H. A meta-analysis of diffusion tensor imaging studies in amyotrophic lateral sclerosis. Neurobiol Aging 2012; 33:1833–1838.
17. Pan PL, Song W and Shang HF. Voxel-wise meta-analysis of gray matter abnormalities in idiopathic Parkinson's disease. Eur J Neurol 2011; 19:199-206.
18. Bora E, Fornito A, Yücel M and Pantelis C. The effects of gender on grey matter abnormalities in major psychoses: a comparative voxelwise meta-analysis of schizophrenia and bipolar disorder. Psychol Med 2011; 42:295-307.
19. Nakao T, Radua J, Rubia K and Mataix-Cols D. Gray matter volume abnormalities in ADHD: Voxel-based meta-analysis exploring the effects of age and stimulant medication. Am J Psychiatry 2011; 168:1154-1163.
20. Murphy ML and Frodl T. Meta-analysis of diffusion tensor imaging studies shows altered fractional anisotropy occurring in distinct brain areas in association with depression. Biol Mood Anxiety Disord 2011; 1:3.
21. Fusar-Poli P, Radua J, McGuire P and Stefan B. Neuroanatomical maps of psychosis onset: Voxel-wise meta-analysis of antipsychotic-naive VBM studies. Schizophrenia Bull 2012; 38:1297-1307.
22. Frodl T and Skokauskas N. Meta-analysis of structural MRI studies in children and adults with attention deficit hyperactivity disorder indicates treatment effects. Acta Psychiatr Scand 2012; 125:114-26.
23. Fusar-Poli P. Voxel-wise meta-analysis of fMRI studies in patients at clinical high risk for psychosis. J Psychiatry Neurosci 2012;37:106-12.
24. Li J, Pan P, Huang R and Shang H. A meta-analysis of voxel-based morphometry studies of white matter volume alterations in Alzheimer's disease. Neurosci Biobehav R 2012 Feb;36(2):757-63.
25. Fusar-Poli P, Smieskova R, Serafini G, Politi P and Borgwardt S. Neuroanatomical markers of genetic liability to psychosis and first episode psychosis: A voxelwise meta-analytical comparison. World J Biol Psychia 2012; in Press.
26. Palaniyappan L, Balain V, Radua J and Liddle PF. Structural correlates of auditory hallucinations in schizophrenia: A meta-analysis. Schizophr Res 2012; 137:169–173.
27. Richlan F, Kronbichler M and Wimmer H. Structural abnormalities in the dyslexic brain: A meta-analysis of voxel-based morphometry studies. Hum Brain Mapp 2012; in Press.
28. Pan PL, Song W, Yang J, Huang R, Chen K, Gong QY, Zhong JG, Shi HC and Shang HF. Gray matter atrophy in behavioral variant frontotemporal dementia: a meta-analysis of voxel-based morphometry studies. Dement Geriatr Cogn Disord 2012; 33:141-8.
29. Palaniyappan L, Balain V and Liddle PF. The neuroanatomy of psychotic diathesis: A meta-analytic review. J Psychiatr Res 2012; 46:1249–1256.
30. Bohrn IC, Altmann U and Jacobs AM. Looking at the brains behind figurative language - A quantitative meta-analysis of neuroimaging studies on metaphor, idiom, and irony processing. Neuropsychologia 2012; 50:2669–2683.
31. Hart H, Radua J, Mataix-Cols D and Rubia K. Meta-analysis of fMRI studies of timing in attention-deficit hyperactivity disorder (ADHD). Neurosci Biobehav Rev 2012; 36:2248-56.
32. Lai CH. Gray matter volume in major depressive disorder: a meta-analysis of voxel-based morphometry studies. Psychiatry Res 2013; 211:37-46.
33. Peng Z, Lui SS, Cheung EF, Jin Z, Miao G, Jing J and Chan RC. Brain structural abnormalities in obsessive-compulsive disorder: converging evidence from white matter and grey matter. Asian J Psychiatr 2012; 5:290-296.
34. Pan PL, Shi HC, Zhong JG, Xiao PR, Shen Y, Wu LJ, Song YY, He GX and Li HL. Gray matter atrophy in Parkinson's disease with dementia: evidence from meta-analysis of voxel-based morphometry studies. Neurol Sci 2013; 34:613-619.
35. Pan P, Shi H, Zhong J, Xiao P, Shen Y, Wu L, Song Y and He G. Chronic smoking and brain gray matter changes: evidence from meta-analysis of voxel-based morphometry studies. Neurol Sci 2012; in Press.
36. Hart H, Radua J, Nakao T, Mataix-Cols D and Rubia K. Meta-analysis of functional magnetic resonance imaging studies of inhibition and attention in attention-deficit/hyperactivity disorder: exploring task-specific, stimulant medication, and age effects. JAMA Psychiatry 2013; 70:185-98.
37. Lansley J, Mataix-Cols D, Grau M, Radua J and Sastre-Garriga J. Localized grey matter atrophy in multiple sclerosis: A meta-analysis of voxel-based morphometry studies and associations with functional disability. Neurosci Biobehav Rev 2013; 37:819-830.
38. Ersche KD, Williams GB, Robbins TW and Bullmore ET. Meta-analysis of structural brain abnormalities associated with stimulant drug dependence and neuroimaging of addiction vulnerability and resilience. Curr Opin Neurobiol 2013; in Press.
39. Jacobs HI, Radua J, Lückmann HC and Sack AT. Meta-analysis of functional network alterations in Alzheimer's disease: Toward a network biomarker. Neurosci Biobehav Rev 2013; 37:753-765.
40. Sartory G, Cwik J, Knuppertz H, Schürholt B, Lebens M, Seitz RJ and Schulze R. In search of the trauma memory: a meta-analysis of functional neuroimaging studies of symptom provocation in posttraumatic stress disorder (PTSD). PLoS One 2013; 8:e58150.
41. Shi HC, Zhong JG, Pan PL, Xiao PR, Shen Y, Wu LJ, Li HL, Song YY, He GX and Li HY. Gray matter atrophy in progressive supranuclear palsy: meta-analysis of voxel-based morphometry studies. Neurol Sci 2013; in Press.

Do you know other published studies using SDM? Please tell us HERE !