More than sensory stimuli, odorous stimuli were employed to facilitate the evocation of emotional responses in the present study. The odor-stimulated emotion was evaluated by investigating specific features of encephalographic (EEG) responses produced thereof. In this study, the concentrations of the same odor were altered; viz., the changes in odor-induced emotional level were compared with the concurrently monitored EEG response features. In addition, we performed the mental task to evoke the arousal state of the brain and investigated the resemblance of response characteristics of the resting state to the post-mental task resting state.