Jeremy,
First, your 3dAnova setup sounds correct. You just need to be looking at the interaction term; the ISI (jittered or fixed) X performance (hits or misses). The voxels that are significant for the interaction indicate ones that show hits vs miss activity that is different for jittered or fixed ITI. I believe this is the question you are trying to answer.
Second, to do a conjunction analysis threshold your hits versus misses contrast (paired t-test) for the fixed ISI and for the jittered ISI. This will leave only voxels that show significant differences between hits and misses (use 3dmerge –1thresh option for this). Next turn your fixed and jittered thresholded maps into masks and overlap them using 3dcalc.
3dcalc –a fixed_ISI_thresholded+tlrc –b jittered_ISI_thresholded+tlrc –expr “(step(a))+(2*(step(b)))” –prefix fixed_versus_jittered_conjunction
Above the ‘step’ function creates a mask of all voxels, that is, those that were significant and thresholded with 3dmerge. By adding ‘a’ (fixed ISI) to ‘2*b’ you are creating a conjunction map where voxels that are =1 are those only active for the fixed ISI, those =2 are active for the jittered ISI, and those =3 are active in both ISI conditions. Those =0 are not active in either condition.
Adjust your intensity color bar so that the value 1 gets 1 color, value 2 gets another color, and value 3 gets a third color.
Hope this helps,
Christine
