Autonomic Nervous System Responses to Odours: the Role of Pleasantness and Arousal

Abstract

Perception of odours can provoke explicit reactions such as judgements of intensity or pleasantness, and implicit output such as skin conductance or heart rate variations. The main purpose of the present experiment was to ascertain: (i) the correlation between odour ratings (intensity, arousal, pleasantness and familiarity) and activation of the autonomic nervous system, and (ii) the inter-correlation between self-report ratings on intensity, arousal, pleasantness and familiarity dimensions in odour perception. Twelve healthy volunteers were tested in two separate sessions. Firstly, subjects were instructed to smell six odorants (isovaleric acid, thiophenol, pyridine, L-menthol, isoamyl acetate, and 1-8 cineole), while skin conductance and heart rate variations were being measured. During this phase, participants were not asked to give any judgement about the odorants. Secondly, subjects were instructed to rate the odorants on dimensions of intensity, pleasantness, arousal and familiarity (self-report ratings), by giving a mark between 1 (not at all intense, arousing, pleasant or familiar) and 9 (extremely intense, arousing, pleasant or familiar). Results indicated: (i) a pleasantness factor correlated with heart rate variations, (ii) an arousal factor correlated with skin conductance variations, and (iii) a strong correlation between the arousal and intensity dimensions. In conclusion, given that these correlations are also found in other studies using visual and auditory stimuli, these findings provide preliminary information suggesting that autonomic variations in response to olfactory stimuli are probably not modality specific, and may be organized along two main dimensions of pleasantness and arousal, at least for the parameters considered (i.e. heart rate and skin conductance).

Hedonic Olfactory Perception in Depression: Relationship between Self-Evaluation and Autonomic Response

“…HR was measured continuously throughout the session. The HR score of each subject and for each stimulus was calculated by subtracting the mean rate for the 3 s preceding flask presentation from that for the 8 s after odour stimulation as described previously (Bensafi et al, 2002a;2002b). After the HR variation measurements, the subject smelled each flask again and evaluated the pleasantness of the odour using a linear scale labeled at each end (highly unpleasant/highly pleasant), resulting in a hedonic subjective score ranging from 0 to 10 (cm).…”

Instantaneous Assessment of Hedonic Olfactory Perception Using Heartbeat Nonlinear Dynamics: a Preliminary Study

“…Particularly, a study on food fragrances showed that an early ANS response (after 1s) reflects the odors arousal, whereas delayed ANS responses (after 3-4s) reflect the odors valence [3]. Also, odor pleasantness correlated with heart rate variations [5,9], and flower smells induced a significant increase in the parasympathetic activity [4].…”

“…This has anatomical foundations in the connection between the olfactory neural path and brain areas such as amygdala and hippocampus, known to be involved in emotional processing [2]. As these limbic regions are also involved in the regulation of the endocrine system and the Autonomic Nervous System (ANS), the current literature consistently reports on changes in peripheral physiological dynamics during olfactory perception [3][4][5][6][7][8]. Particularly, a study on food fragrances showed that an early ANS response (after 1s) reflects the odors arousal, whereas delayed ANS responses (after 3-4s) reflect the odors valence [3].…”

Chemical Composition and Effects of Blended Essential Oil on Humans

“…breathing rate, blood pressure, pulse rate, skin temperature and skin conductance, changes in brain wave activities, e.g. electroencephalogram, contingent negative variation, changes in mood, cognitive performances and emotion (Bensafi et al, 2000;Diego et al, 1998;Heuberger et al, 2000;Heuberger et al, 2006;Hongratanaworakit et al, 2005;Hongratanaworakit et al, 2007;Hongratanaworakit, 2009;Hongratanaworakit, 2010;Inoue et al, 2003;Moss et al, 2003;Rutledge and Jones, 2007). However, up to now, no experiments about the effects of blended oil on human autonomic parameters and on emotional changes after inhalation have been carried out.…”