Olfactory sensation emotion regulation: The implicit emotion regulation function of positive olfactory stimuli during emotional picture processing

Previous research has shown that olfactory stimuli can induce emotional states, physiological and neural responses related to emotions. It remains unclear whether positive olfactory stimuli could down-regulate individuals' negative emotions or up-regulate individuals' positive emotions in an unconscious way. The present study investigated the effects of emotional olfactory stimuli on the behavioral and electrophysiological responses to emotional pictures. Forty participants were exposed to different types of odor conditions (neutral, pleasant, unpleasant) and evaluated the emotional pictures' valence and arousal while electroencephalography was recorded. Behavioral results showed that participants reported more positive emotions in response to positive pictures in two types of pleasant odor conditions (especially the citrus) than in unpleasant or neutral odor conditions. However, the pleasant odor (lavender) increased the positive pictures' valence scores but decreased the positive pictures' arousal scores. The ERPs results showed that the pleasant odors reduced the amplitudes of N1 and EPN components in response to negative pictures, indicating that pleasant odors might down-regulate negative emotions through decreasing attentional capture for negative visual stimuli during the early stage. The pleasant odor (lavender) attenuated LPP amplitudes for emotional pictures, suggesting that the positive olfactory stimuli might be helpful to down-regulate the emotional arousal by reducing attentional deployment to negative visual stimuli during the late stage of emotional visual stimuli processing. These findings provided novel behavioral and neurophysiological evidence that positive olfactory stimuli modulated visual emotional processing across multiple stages, and suggested that olfactory sensation could function as a rapid and relatively effortless emotion regulation modality.