Dear SPM experts,
I am working on a VBM analysis using SPM 12 and so far everything is going smoothly. The nature of my analysis is looking at the relationship between grey matter volume and a performance measure. Because of relative scarcity of information in the domain that I am investigating, I would like to provide some more complementary evidence and I would have a few questions related to deformation based and tensor-based morphometry.
1- Reading through some of the existing publications, they do not specifically outline how to implement these methodologies with SPM, does anyone know of an existing manual like John Ashburner's VBM manual? If not, could anyone give me some suggestions about how to implement any of these in a straightforward way (preferably pointing out to similarities and differences to the stages of VBM with DARTEL)
2- To me it is easier to interpret the VBM results, but what can we really say if a performance measure is correlated with the extent of deformations in a specific area? Does this mean that asymmetry (?) in that area is predictive of the performance measure?
For example, in this paper from Matthew Rushworth's group, what is the additional benefit of using DBM over VBM, I could not get my head around to fully interpret the advantages.
3- My understanding at this stage may be limited but I thought TBM is a better candidate to complement VBM results, as based on my understanding it still deals with the variability in volume of specific brain structures. In that respect, and if my understanding is correct (!), do you think doing a TBM analysis within a specific ROI defined by the significant VBM clusters would be a solid approach to provide some further complementary results?
4- Based on the literature that I come across with, people tend to stick with one of these methodologies and I haven't seen any papers which report results from multiple morphometric methodologies. Does this implicitly suggest that the methodologies do not communicate well with each other or simply the additional information becomes somewhat redundant and unnecessary to analyse and report.
I am looking forward to hearing your thoughts and recommendations
Many thanks in advance,
All the best,
Erdem
