Background: Pain is a subjective experience characterized by sensory (intensity) and emotional (unpleasantness) aspects. Although literature reports behavioural effects on pain due to smell and taste influence, to our knowledge the relationship between tonic pain induced by a capsaicin cream and these chemosensory systems has never been explored before. The aim of this study was to investigate the modulation of olfactory and gustatory substances having different valence on tonic pain perception mediated by a capsaicin cream application. Methods: Sixty healthy volunteers were included in two separated experiments (N = 30 smell; N = 30 taste) and underwent different valence smell and taste stimulations, while receiving painful stimuli. Perception of pain intensity (the sensory component) and unpleasantness (the affective component) was measured with a numerical rating scale, both during the two aforementioned experiments. Results: Pain unpleasantness rating showed differences only in the smell experiment between the two odourous conditions. In particular, pleasant odour induced lower ratings of pain unpleasantness, while no significant results were found for intensity. Regarding taste, we could not observe significant effects nor for pain unpleasantness or intensity. Conclusions: These findings highlight the potential role of pleasant odours in influencing the affective aspects of pain perception induced by this kind of tonic pain. Such evidence might provide new insight for using chemosensory substances as analgesics for modulating the cognitive aspects of neuropathic pain. Significance: This work shows the effect of smell on the emotional component of tonic pain, experimentally induced by capsaicin cream application. Previous literature investigated tonic pain in interaction with smell and/or taste stimuli, but mainly with physical methods such as temperature. Our findings add new information in this field, contributing to a deeper insight on the role of olfaction on this particular kind of tonic pain perception. This approach could open to new investigations aimed to consider odours for pain management.

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Every day our sensory systems perceive and integrate a variety of stimuli containing information vital for our survival. Pain acts as a protective warning system, eliciting a response to remove harmful stimuli; it may also be a symptom of an illness or present as a disease itself. There is a growing need for additional pain-relieving therapies involving the multisensory integration of smell and taste in pain modulation, an approach that may provide new strategies for the treatment and management of pain. While pain, smell, and taste share common features and are strongly linked to emotion and cognition, their interaction has been poorly explored. In this review, we provide an overview of the literature on pain modulation by olfactory and gustatory substances. It includes adult human studies investigating measures of pain threshold, tolerance, intensity, and/or unpleasantness. Due to the limited number of studies currently available, we have structured this review as a narrative in which we comment on experimentally induced and clinical pain separately on pain-smell and pain-taste interaction. Inconsistent study findings notwithstanding, pain, smell, and taste seem to interact at both the behavioral and the neural levels. Pain intensity and unpleasantness seem to be affected more by olfactory substances, whereas pain threshold and tolerance are influenced by gustatory substances. Few pilot studies to date have investigated these effects in clinical populations. While the current results are promising for the future, more evidence is needed to elucidate the link between the chemical senses and pain. Doing so has the potential to improve and develop novel options for pain treatment.

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2020) 'Boundaries in spatial cognition : looking like a boundary is more important than being a boundary.', Journal of experimental psychology : language, memory, and cognition., 46 (6).The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTLarge walls and other typical boundaries strongly influence neural activity related to navigation and the representations of spatial layouts. They are also major aids to reliable navigation behavior in young children and non-human animals. Is this because they are physical boundaries (barriers to movement), or because they present certain visual features, such as visually extended 3D surfaces? Here, these two factors were dissociated by using immersive virtual reality and real boundaries. Eighty adults recalled target locations in one of four environments: plywood, where a virtual wall coincided with a large piece of real plywood; pass through, where the virtual wall coincided with empty space and participants could pass through it; pass over, where the virtual wall was projected downward to be visible underneath a transparent floor; and cones, where the walls were replaced with traffic cones. One condition had features that were boundaries and looked like boundaries (plywood); two had features that were not boundaries but looked like boundaries (pass over/through); and one had features that were not boundaries and did not look like boundaries (cones). The precision and bias of responses changed only as a function of looking like a boundary. This suggests that variations in spatial coding are more closely linked to the visual properties of environmental layouts than to whether they contain physical boundaries (barriers to movement).