These ANOVAs were conducted for two main reasons. First, the voxel-wise analyses only isolated regions that were differentially sensitive to arousal level (i.e., high-arousal vs. low-arousal conditions) or valence within each sensation-seeking group or in the group comparison, but did not consider the fMRI response relative to the fixation baseline. The ROI analyses used fMRI signal for each arousal condition relative to the fixation baseline, rather than fMRI signal in the high-arousal condition relative to the low-arousal condition. The assumption was that fixation-baseline response would be less influenced by sensation-seeking status than the response to low-arousal stimuli would be (see Zuckerman, 2005). Second, a differential response to arousal or valence level in the voxel-wise analysis of a region would not necessarily imply that the region was activated more than during the baseline. A region could show a negative signal change relative to the fixation baseline even if it responded differentially to high-arousal versus low-arousal stimuli or to positive versus negative high-arousal stimuli. ROIs that showed a negative signal change for all conditions were not interpreted further.1
