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A slightly more extended answer is that when in doubt you can always use the 'Verify data identity' option in the BMS tool. In this case it should be OK as Chris said. Regarding different sessions I think it's more an interpretation question of whether stimulating the left and right ear can be considered as a repetition of the same thing or maybe you could treat the two hemispheres as separate subjects as is customary in some fields. Or you could indeed do two separate analyses for all left and all right sides. It all depends on what you expect your reviewers to like more. Best, Vladimir On 10 Jan 2013, at 09:12, Christophe Phillips <[log in to unmask]> wrote: > Dear Doug, > > Simple answer is, yes you can compare (with BMS) models with different input setup. > > HTH, > Chris > > Le 10/01/2013 9:17, Doug Davidson a écrit : >> Dear SPM list, >> >> Is it possible to compare DCMs with different exogenous input (one versus two) using BMS? >> >> In our experiment, subjects heard either left ear or right ear stimulation (i.e., monaural tones) and we recorded MEG. We would like to construct different DCM models for the evoked response. The models include two sources: left and right temporal cortex. I would like to compare models with different specifications of the input: One DCM has a single input to both left and right sources (DCM.C=[1 1]'), while a second DCM has one input to the left and another input to the right (DCM.C=[1 0; 0 1]). We are trying to test whether the dual input model will provide a better account of the response. >> >> I have fit these models, and both seem to capture the main data pattern, but I would like to compare them with BMS. For a given condition (e.g., left ear stimulation), I construct both the unitary input model and the dual input model. The only difference is the specification of the input. Can I use BMS to compare these different input patterns? >> >> If I do the same for the other condition (e.g., right ear stimulation), can I then add this second condition as another session in the BMS, or is it better to run a separate BMS for each? >> >> Thanks a lot for your help. >> >> -Doug >> >> Doug Davidson >> Basque Center on Cognition, Brain and Language >> Basque Country, Spain >>