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ABSTRACT

Emotion regulation is defined as an important mechanism for human adaptation. fMRI studies have recently highlighted its neural bases but most research uses visual stimulation to induce emotion, none of them using odorant stimulations. Nevertheless, olfaction is intimately linked to emotional processes, sharing some same neural bases and thus constitutes a valuable emotion-inducer in experimental conditions. The present study aims to determine the cerebral areas which might be involved in downregulation, using pleasant and unpleasant odours as emotion-inducers. Eighteen subjects were scanned during 2 sequences of 12 stimulations, each with either a pleasant or an unpleasant odour. For one sequence, subjects were instructed to naturally experience their emotion induced by odour inhalation and for the other one, to decrease the intensity of their emotion. Consistent with previous work using emotion-inducers, emotion regulation resulted in higher activations of the dorsolateral prefrontal cortex and the anterior insula, but in lower activation of the amygdala. However, some areas (the posterior cerebellum and the orbitofrontal cortex) are less activated during regulation compared to maintain and thus appear to be specific to odorant stimulations. Finally the hedonic valence of the odour determines activations in different brain areas such as the supplementary motor area and the posterior cingulum. Thus, this study suggests abilities to regulate emotion in response to odours, involving brain areas usually described in the literature for other emotional stimuli, but also specific areas depending partly of the hedonic valence of the odour.

4. Discussion

The aim of this study was to highlight neural substrates of emotion regulation towards odorant stimulations. The perceptual processing of emotions and odours is dominated by its hedonic feature (pleasantness/unpleasantness) but odours as emotioninducers have been rarely used in the literature on emotion regulation. Ratings of pleasantness by participants clearly shows that the two odours have opposite hedonic features. The present experiment is the first attempt to our knowledge to describe the neural networks involved with olfactory cues. First of all, the results obtained in the present experimental conditions show a strong preference for distraction when participants had to decrease emotions induced by odorants. In their study, Adolph and Pause (2012) [20] showed that subjects had a mild preference for self-focused reappraisal compared to situation-focused reappraisal, but participants had to use a reappraisal strategy. On the contrary, in the present study, they were free to use any strategy. Distraction was not shown as more efficient than reappraisal in other experimental conditions [37]. However, it could appear to be more efficient in everyday life experiences [38] and is less costly in cognitive resources, which can explain the choice of our subjects. Further studies would be of interest to investigate the preferential strategies, and their efficiencies, in down- or up-regulation spontaneously used by subjects in response to odours compared to visual cues, for example. It cannot be excluded that distraction could be a more efficient strategy when olfactory cues are concerned due to their specific cerebral pathways.