Smells Influence Perceived Pleasantness but Not Memorization of a Visual Virtual Environment.

The present study aimed to investigate whether the perception of still scenes in a virtual environment in congruent versus incongruent condition can be influenced by odors. Ninety healthy participants were divided into three groups, including two experimental virtual reality (VR) environments: a rose garden, an orange basket, and a control condition. In each VR condition, participants were exposed to a rose odor, an orange odor, or no odor, resulting in congruent, incongruent, and control conditions. Participants were asked to describe (a) the content of the VR scene and rate its overall pleasantness and (b) the smell and to rate its intensity and pleasantness. For each condition, participants were tested twice. During the second test, participants provided ratings and descriptions of the content of the VR scenes without being exposed to odors or VR environments. Virtual scenarios tended to be remembered as more pleasant when presented with congruent odors. Furthermore, participants used more descriptors in congruent scenarios than in incongruent scenarios. Eventually, rose odor appeared to be remembered as more pleasant when presented within congruent scenarios. These findings show that olfactory stimuli in congruent versus incongruent conditions can possibly modulate the perception of the pleasantness of visual scenes but not the memorization.

Visual Priming Influences Olfactomotor Response and Perceptual Experience of Smells.

Whereas contextual influences in the visual and auditory domains have been largely documented, little is known about how chemical senses might be affected by our multisensory environment. In the present study, we aimed to better understand how a visual context can affect the perception of a rather pleasant (floral) and a rather unpleasant (damp) odor. To this end, 19 healthy participants performed a series of tasks including odor detection followed by perceptual evaluations of odor intensity, pleasantness, flowery, and damp characters of both odors presented at 2 different concentrations. A visual context (either congruent or incongruent with the odor; or a neutral control context) preceded odor stimulations. Olfactomotor responses as well as response times were recorded during the detection task. Results showed an influence of the visual context on semantic and motor responses to the target odors. First, congruency between context and odor increased the saliency of the olfactory feature of the memory trace, for the pleasant floral odor only (higher perceived flowery note). Clinical applications of this finding for olfactory remediation in dysosmic patients are proposed. Second, the unpleasant odor remained unaffected by visual primes, whatever the condition. In addition, incongruency between context and odor (regardless of odor type) had a disruptive effect on odor sampling behavior, which was interpreted as a protective behavior in response to expectancy violation. Altogether, this second series of effects may serve an adaptive function, especially the avoidance of, or simply vigilance toward, aversive and unpredictable stimuli.

Brain volume changes in hyposmic patients before and after olfactory training.

OBJECTIVES/HYPOTHESIS: Olfactory dysfunction is thought to be associated with reduced gray matter (GM) volume in olfactory-related brain areas. The aim of this study was to determine GM structural changes within olfactory-related regions of the brain in patients with smell loss due to upper respiratory tract infection (URTI) before and after olfactory rehabilitation. STUDY DESIGN: Prospective intervention case-control study. METHODS: Magnetic resonance imaging structural brain images were collected from 30 patients with smell loss due to URTI and 31 controls. Patients exposed themselves to odors (olfactory training [OT]) over 12 weeks and then were rescanned. Olfactory testing was performed using the validated Sniffin' Sticks test. GM was investigated with voxel-based morphometry. RESULTS: GM volumes were found to be reduced in the limbic system and thalamus among pretraining patients compared to controls; in patients, OT was associated with a significant increase of GM volume in these two regions. The GM volume within other olfactory-related regions was not different between patients and controls. In addition, no relevant difference between the GM volume pre- and post-OT was observed in primary olfactory-related regions. CONCLUSIONS: OT was associated with an increase in GM volume of the hippocampus and the thalamus, possibly pointing toward a strategy for more effective exploitation of olfactory signals based on a higher degree of attention toward odors and association of memories with olfactory input. LEVEL OF EVIDENCE: 3b. Laryngoscope, 128:1531-1536, 2018.