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Dear SPM experts, I have run an fMRI study on 12 subjects with (among others) the following 3 conditions: (1) a motor coordination task (2) a visual search task (3) tasks 1 and 2 performed simultaneously (dual-task condition) Using RFX analysis for group results, I have observed some "strange" deactivations in 3 different areas of the prefrontal cortex during the dual-task condition, i.e. the prefrontal areas are activated in single tasks 1 and 2, and deactivated in dual-task. As I have used proportional scaling at first-level analysis, I was wondering whether these deactivations could be explained by a relative increase of the global signal in the dual-task condition relative to other conditions? and if this makes sense, should proportional scaling be used in my particular experiment? Any help or advice would be greatly appreciated. Florence Remy, Ph.D. Motor Control Lab KULeuven, Belgium