I am performing vertex based cortical analyses, but am also interested in effects in specific subcortical regions (e.g. hippocampus and amygdala) for which I am performing ROI analyses. I am wondering how to control my vertex based analyses for my ROI analyses and vice versa. Do I simply perform an FDR or Bonferroni correction of the (clusterwise) p-values or is there a different way to approach this?
Any thoughts are much appreciated!
I am wondering how to control my vertex based analyses for my ROI analyses and vice versa.
It is not clear to me what you mean above. Could you elaborate a little more?
Sorry, I meant how to correct the p-value of my vertex based analyses for additional ROI analyses, and vice versa: how do I correct the p-value of my ROI analyses for the vertex based analysis I also performed. Does that make more sense?
I’m still lost. Could you explain the details of both your vertex based analyses and the ROI analyses?
I am interested in the effect of an exposure on brain functioning. Effects on the cortex are assessed using vertex based whole brain analyses. For my subcortical ROI analyses, I have extracted summary statistics and am performing regression analyses in a general statistical software.
In all, I am performing a whole brain surface based analysis, plus 4 regression analyses. All analyses are answering the same research question (effect of exposure on brain functioning), so it is my understanding that it would be good practice to correct my p-values (or alpha’s) for all the analyses I am performing.
My question is, how do I correct the p-value (or alpha) of my regression analyses for the other analyses? I am performing four regression analyses + a cluster corrected whole-brain analysis. Would I perform a Bonferroni correction? If yes, does 4 ROI analyses + a cluster corrected whole brain analysis equal 5 analyses (so my alpha would be .05/5=.01)? Or does the whole brain analysis get a different weight? Would I apply the same threshold to my vertex based analysis (so cluster corrected threshold of .01 instead of .05)?
Or is Bonferroni too strict?
I think it hasn’t been common practice to correct for multiple testing over and above the correction for multiple comparisons done within a single (whole-brain) voxel/vertex based analysis, but I am trying to figure out what could be done to more properly control for the number of tests/comparisons that I perform to answer a single research question. Any thoughts would be helpful!
As you’ve already realized, there is no effective way to correct for such parallel analyses (node-wise plus subcortical ROIs) under the conventional testing framework. I would just perform the correction separately: one on the surface, and one for those four ROIs. Ideally it would be better and more efficient to analyze all the data (cortical and subcortical) in one model.