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 , Am J Psychiatry , Neurosci Biobehav R , Biol Psychiat , Schizophrenia Bull , Br J Psychiat , Neurobiol Aging , Neuroimage , Psychol Med , Schizophr Res , J Psychiatry Neurosci , J Clin Psychopharmacol , Acta Psychiatr Scand , J Affect Disorders , Eur J Neurol , Eur Psychiat , Amyotroph Lateral Sc or World J Biol Psychia or Biol Mood Anxiety Disord .

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. Radua J and Mataix-Cols D. Meta-analytic methods for neuroimaging data explained. Biol Mood Anxiety Disord 2012; 2:6. (introduction to voxel-based meta-analyses)
2. 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. (SDM method 1/3: original algorithms)
3. 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. (SDM method 2/3: comparisons and linear models)
4. 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 2011; in Press. (SDM method 3/3: effect-sizes and variances)
5. 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. (SDM specific white matter template)
6. 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; in Press. (SDM specific TBSS preprocessing and template)

Other studies using SDM:

7. 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.
8. 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.
9. 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.
10. Richlan F, Kronbichler M and Wimmer H. Meta-analyzing brain dysfunctions in dyslexic children and adults. Neuroimage 2011; 56:1735-42.
11. 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.
12. Lai CH. Gray matter deficits in panic disorder: a pilot study of meta-analysis. J Clin Psychopharmacol 2011; 31:287-93.
13. 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.
14. 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 2011; in Press.
15. 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.
16. 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.
17. 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.
18. 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.
19. 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 2011; in Press.
20. 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.
21. 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.
22. 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.
23. 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.
24. Palaniyappan L, Balain V, Radua J and Liddle PF. Structural correlates of auditory hallucinations in schizophrenia: A meta-analysis. Schizophr Res 2012; in Press.

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

The authors | IoP King's College London | NeuroImageN