Hi everyone, I have a methodological question to ask. It's my first time performing GLM on SPM12. I'll be measuring BOLD signal over 2x3 ANOVA. Normally, I have 6 conditions, however, if I take the side where the stimulus is shown into consideration, I happen to have 12 conditions.
When I have 6 conditions, I'll have 6 onset points per condition. But if I go with 12 conditions, then only three onset points I will add to each predictor(i. e. condition).
From the fmri course, we learnt that the less parameters you have the better estimate you'll get. Then six conditions would yield better estimates. However, because it is a visual perception experiment, the BOLD signal I'd get from whole brain will differ due to the display side of the stimulus (i. e. on the right or on the left). Thus, having 6 conditions might increase noise and decrease true signal.
As you can see, I am a bit confused about what to do, could you give any advice?
Cheers~
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