Voxel-wise analyses isolated brain regions associated with differential sensitivity to high-arousal stimuli (see Table 1). The first analysis compared brain activation for high- versus low- arousal stimuli separately within each sensation-seeking group to assess sensitivity to high-arousal stimuli. The baseline level of cortical arousal is not expected to vary with sensation seeking (Zuckerman, 2005). However, should differences in baseline level of arousal exist, this within-groups analysis would not confound differential sensitivity to high-arousal stimuli with baseline differences in response to low-arousal stimuli. In this first analysis, both HSSs and LSSs showed strong fMRI responses to high-arousal stimuli. In addition to the regions highlighted in Table 1, this analysis revealed activation in the bilateral temporal pole and thalamus for HSSs. The reverse contrast of low-arousal pictures versus high-arousal pictures did not yield any clusters of activation when the same statistical threshold was used. This outcome was expected, given previous findings that the low-arousal stimuli from the IAPS produce less potent autonomic and electroencephalographic responses than the high-arousal stimuli (Cuthbert, Schupp, Bradley, Birbaumer, & Lang, 2000).
