Neuroimaging meta-analyses tend to not use the same methodology as is used in meta-analyses in other disciplines.
Because neuroimaging is primarily concerned with identifying the neural coordinates of a physical, mental, or perceptual process, a different methodological approach is required; one that can estimate an effect-location in the brain as opposed to an effect-size.
Meta-analyses concerned with effect location take data from existing studies to ask two questions: where do the foci converge by synthesizing foci (singular, focus) or the x, y, z atlas coordinates of activation peaks, and where do the images converge by synthesizing statistical maps.
Combining the effect-locations in the form of foci or statistical maps from individual studies can give researchers a more accurate estimation of the effect-location, overcoming some of the limitations associated with single-study neuroimaging results such as small sample size, low power, high rate of false positives, low test-retest reliability, poor reproducibility, and failure to adequately correct for multiple comparisons. (Samartisidis et al. 2017)
Equally important to understand is that meta-analysis methodology for neuroimaging is an active and evolving area of research.
Effect size captures the direction and magnitude of the relationship between two entities. A forest plot is a graphical representation typically used in meta-analyses to report effect sizes across studies.
Harrer, M., Cuijpers, P., Furukawa, T.A., & Ebert, D.D. (2021). Doing Meta-Analysis with R: A Hands-On Guide. Boca Raton, FL and London: Chapman & Hall/CRC Press. ISBN 978-0-367-61007-4.
Effect-location is a short-hand way to describe the goal of a neuroimaging meta-analysis in which the aim is to locate regions where different studies agree on the location of activation peaks (foci) better than expected by chance alone.
Tench, C. R., Tanasescu, R., Auer, D. P., Cottam, W. J., & Constantinescu, C. S. (2014). Coordinate based meta-analysis of functional neuroimaging data using activation likelihood estimation; full width half max and group comparisons. PloS One, 9(9), e106735. https://doi.org/10.1371/journal.pone.0106735
Image-based meta-analyses (IBMA) or also sometimes called 'mega-analyses' are the ideal method of analysis when the full T-statistic images are available. (Say in Neurovault)
Where do the images converge?
The use of full image data prevents the loss of information that has been observed when only foci are used. However, until the sharing of full statistical maps with effect magnitude estimates and standard errors for single studies becomes the norm, researchers conducting meta-analyses may only have access to location information in the form of a list of foci. (Salimi-Khoshidi et al. 2009)
Coordinate-based meta-analyses use foci as data and are the most common methodology used in neuroimaging meta-analysis. Foci data is readily available in neuroimaging literature and tools such as NeuroSynth, NeuroQuery, and BrainMap have made it easy to source imaging studies by topic or region of interest.
Reference: Samartsidis, P., Montagna, S., Nichols, T. E., & Johnson, T. D. (2017). The coordinate-based meta-analysis of neuroimaging data. Statistical Science: A Review Journal of the Institute of Mathematical Statistics, 32(4), 580–599. https://doi.org/10.1214/17-STS624