Hedione Reduces Subjective Vicarious Stress

Effects of the odorant Hedione on the human stress response

Olfactory cues can affect subjective and autonomic manifestations of the human stress response, but evidence of altered endocrine stress reactivity is inconclusive. In the present study, we investigated effects of the odorant Hedione on the human stress response. We exposed 56 women in their follicular phases to a stressor in a room scented with Hedione or no odor. Subjective stress was captured via repeated self-report measurements and the assessment of anticipatory appraisal. As physiological markers of stress, we assessed blood pressure, salivary cortisol and alpha-amylase. The odorant enhanced the cortisol and cardiovascular stress response while leaving subjective stress unaffected. Our results provide evidence for a modulation of the human response to acute psychosocial stress by Hedione. A potential mechanism underlying this effect is Hedione targeting the hypothalamus via binding to the VN1R1 receptor, which is expressed on the human nasal mucosa.

Odours as context cues of emotional memories - The role of semantic relatedness

Odours constitute effective context cues, facilitating memory retrieval. Identifying factors which modulate the effectiveness of olfactory context cues can advance the understanding of processes underlying this effect. We hypothesized that the interplay of subjective stress and semantic relatedness between the odour and the learning material would modulate the effectiveness of an olfactory context cue. We further explored the effect of the odorant Hedione, which is a ligand for a putative human pheromone receptor (VN1R1). To this end, 120 participants watched a video of a stressful episode in which visual objects were present, that were either manipulated in the video (central objects) or not (peripheral objects). Participants rated their subjective stress afterwards. After 24 h, recognition and spatial memory of the objects in the video were tested. Ambient during encoding and recall was an odour related to the episode, an unrelated odour, Hedione or no odour. As a result, we observed a narrowing of recognition memory with increased subjective stress elicited by the video - but only if a semantically related odour was ambient. Moreover, higher subjective stress predicted enhanced spatial memory in the no odour condition, but not in presence of a semantically related or unrelated odour. When exposed to Hedione, higher subjective stress predicted impaired recognition and spatial memory of peripheral objects. Our findings stress the importance of considering semantic relatedness between the olfactory context and the encoded episode when applying odours as context cues for emotional or stressful memories.