I have done an experiment with older adults aged 70-85 years (2 groups: cognitively well and Mild Cognitive Impairment). I normalized EPIs to MNI template by first coregistering and segmenting to individual T1s.
I obtained a significant group x working memory load interaction at cluster-corrected threshold. When I looked up the co-ordinate for the global maxima it corresponded to the corpus callosum. The cluster also included anterior cingulate. A ROI analysis in anterior cingulate confirmed suprathreshold voxels.
I expect that because my sample had a fair degree of atrophy including enlarged ventricles that when warped to the standardised template based on young healthy that the corpus callosum was stretched anteriorly and so that is why it "looks" like the activation is in this area.
Would it be helpful to convert the co-ordinates back to native space to get the true co-ordinates for the activity in this sample? Can this be done at the group level?
Alternatively, has anyone got suggestions on how I would report this finding? Is the convention to ignore regions of WM and report to nearest GM?
Many thanks for your suggestions.
PhD student, School of Psychiatry, University of New South Wales