Sorry, forgot to add one additional (related) question: is it ever correct to say "for region Y, the activations found for taskA were smaller than for taskB" just based on the two contrasts *taskA>baseline *and *taskB>baseline*? Or is it necessary that taskA and taskB be contrasted directly to be able to draw any conclusions (if any are sensible) about what smaller/larger activations of a certain region might mean?
Thanks! On 27 August 2015 at 19:13, Francesco Puccettone < francesco.puccett...@gmail.com> wrote: > Hello all, > > I have seen several (older) papers that draw conclusions about the > implication of a brain region in a given task by using the following logic: > region X was activated in the contrast *taskA>baseline*, but not in the > contrast *taskB>baseline*; therefore, region X is implicated in/essential > for the cognitive processes underlying taskA, but not also for that > underlying taskB; in other words, it dissociates between the two tasks. > > I believe Nancy Kanwisher addresses this point in a video lecture where > she was pointing out that the above logic is flawed, and that said > conclusion can only be drawn if the two tasks are contrasted directly ( > *A>B*). Have I understood this correctly, and does it ever make any sense > to draw inferrences about implicated brain regions based on (visually) > comparing the list of regions produced by contrasts comparing each task to > the same baseline (in other words, by noticing which brain regions appear > in one list, but not in the other)? Or, on the contrary, do all statistics > and corrections need to be done voxel-wise, which is something that is only > done when contrasting the two tasks directly? > > Many thanks for any opinions. > > --Francesco >
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