Retronasal Route Research Articles

Short-term olfactory deprivation reorganizes brain activity

IntroductionOlfactory loss (including short-term) initiates neural reorganization processes in the brain, but the central mechanisms of this largely remain unknown.ObjectivesWe aim to conduct a neurophysiological study of neocortical mechanisms for the effects of olfactory sensation on functional activity of human brain under temporary obstruction of nasal breathing.Methods 123 healthy volunteers (76 female and 47 male students aged 18 to 23 years)participated in this study.EEG was registered during the rest state (5 min), olfactory blockage (5 min), under odor stimulation with the lemon essential oil (5 min) and renewal of nasal breathing (5 min). We estimated the spectral power density and the levels of coherence of all the frequencies from 0.2 to 35 Hz.ResultsThe onset of orthonasal olfactory sensory blockage was accompanied by an increase in the power of processes of local synchronization of beta frequency in the caudal regions of the brain, with simultaneous enhancement of the coherence of the theta band in parietal-occipital zones and a certain enhancement of the interfrontal and intrahemispherical left-side and right-side interactions in the beta2-subband. Thus, the sudden cessation of olfactory detection led to activation of thalamo-cortical loops and top-down control systems (search for the olfactory signal): that is an active orienting process (triangle of increase in F4-T4-P4 connections) with emotional coloring (the caudal localization of the coherence changes in the theta band). The prolongation of the nasal blockage, despite the possibility of activation of the retronasal route of odor perception and odorized air, was accompanied by a definite inhibition of distant interactions in the posterior regions of the brain in the theta-band and a significant decrease in right-brain long-distant and parietooccipital beta2-subband functional connectivity. Restoration of nasal breathing and olfactory perception is accompanied by sufficiently powerful activation of interhemispheric long and short distance information interactions in the theta1,2 and beta1 frequency bands.ConclusionsOur data indicated that cessation and restoration of olfactory perception lead to an increase cognitive activity, the development of memory processes, the current sensory and cognitive-emotional control of behavioral reactions, focusing attention, assessment of the significant stimulus.Disclosure of InterestNone Declared

High perceived stress is associated with decreased sensory-specific satiety in humans

Previous studies have shown that chronic stress increases food intake. One possible mechanism may be due to altered sensory-specific satiety (SSS) among people with high level of chronic stress. In the current study, seventy-six participants were divided into either high-stress or low-stress groups according to their Perceived Stress Scale (PSS) scores. Participants were assigned to consume one of two foods (banana milk and corn soup) ad libitum until they felt comfortably satiated. Before and after eating, participants rated their liking and wanting for the flavor and the odor (via retronasal and orthonasal routes) of the eaten and uneaten foods. Individual interoceptive sensibility and eating behavior were measured using the Multidimensional Assessment of Interoceptive Awareness (MAIA) and Reasons Individuals Stop Eating Questionnaire (RISE-Q-15), respectively. Compared to the low-stress group, the high-stress group demonstrated blunted SSS to the whole food flavor. No significant difference was found for olfactory-specific satiety (retronasal or orthonasal) between the two groups. In addition, across the whole sample of participants, MAIA total score was positively associated with the magnitude of SSS (r = 0.29, p = 0.01). These results indicate that chronic perceived stress may play a role in the experience of reward during eating.

Orthonasal and retronasal odor identification in patients with parosmia

ObjectiveTo compare retronasal and orthonasal perception in parosmic COVID-19 patients, in order to determine whether COVID-19 has a differential effect on these functions.MethodsUsing the Sniffin Sticks test battery orthonasal function was examined for odor threshold, discrimination and identification. Retronasal function was assessed using 20 tasteless aromatized powders. Gustatory function was measured using the Taste Strips test.ResultsThis study included 177 patients (127 women, 50 men; mean age 45 years), of whom 127 (72%) were hyposmic and 50 (28%) normosmic. Compared to patients without parosmia, parosmic patients performed worse in odor identification for both orthonasal (F = 4.94, p = 0.03) and retronasal tests (F = 11.95, p < 0.01). However, an interaction effect between route of odor identification (orthonasal or retronasal) and parosmia status was found (F = 4.67, p = 0.03): patients with parosmia had relatively lower retronasal scores than patients without parosmia.ConclusionOur results suggest that COVID-19 may affect the olfactory mucosa differently along the anterior–posterior axis, thereby possibly contributing to the pathophysiology of parosmia. Patients with parosmia also exhibit a higher degree of impairment when odors are presented through the retronasal route during eating and drinking.

A Nasal Aerodynamics Perspective of Retronasal Olfaction: Rodents vs. Humans.

Odor perception can be achieved through ortho or retronasal routes, with the latter being an important component of flavor perception. There are significant olfactory differences that exist between rats and humans and by understanding the role of structural differences, further insight can be gained into the mechanism of odorant perception via ortho or retronasal routes. 3D human and rat (Sprague Dawley) computational models were used to investigate nasal anatomy impact on ortho vs. retronasal odorant transport to the olfactory epithelium. The nasal pharynx region was modified for human and rat models to probe nasal structure impact on ortho vs retro olfaction. 65 odorant absorption rates to the olfactory epithelium were extracted from each model. For human, the retronasal route provided higher peak odorant absorption compared to orthonasal route (left: 90% higher, right: 45% higher), but substantially lowered peak absorption for rat (medial: 97% lower, lateral: 75% lower). For both models, anatomical modification had minimal impact to orthonasal routes, but substantially modulated the retronasal route: decrease (left: -41.4%, right: -44.2%) for human, and increase to the medial (29.5%) but not to lateral (-14.3%) for rat. There exist key differences between humans and rats regarding retro/orthonasal odorant transport routes, which matched well with experimental olfactory bulb activity data in literature. While humans have equivalent odorant delivery between routes, the difference in retro and orthonasal routes in rodents is substantial and changes to the transverse lamina above the nasopharynx can substantially modulate the retronasal route, but not enough to bridge the gap between the two routes.

The presence of chemosensory cues transmitted through the mother's milk increases the search and ingestion responses toward bitter and sour solutions

Olfaction is of major importance during early stages of life in altricial species. This sense allows newborns to develop different behaviors that will allow them to survive. Odors tend to be associated to contextual stimuli (such as warmth); this, in turn, enables the pups to recognize when to withdraw or approach. At the same time, olfaction modulates the acceptance of aversive flavors. The increase of approach responses toward a bitter substance during early life is enhanced by stimulation with familiar, pre-exposed odors. Newborn rats exhibit heightened grasp responses toward an artificial nipple dispensing quinine, and drink more of this bitter solution, in the presence of a pre-exposed odor (lemon or the mother's odor). The present research assessed the replicability of previous results by pre-exposing the subjects to the scent through maternal milk and using solutions with different aversive tastes. Half of the subjects (3 day-old Wistar rats) were pre-exposed to lemon odor through the maternal milk (the mother had previously ingested the lemon essence via an intragastric injection); 4 h later, all the rats were evaluated in the presence of the lemon odor with an artificial nipple containing quinine, citric acid, saline solution, or water. The results showed enhanced seeking and intake of the bitter (quinine) and sour solution (citric acid). However, this did not occur when the nipple contained water or saline solution. The evidence suggests that: During the early stages of development, familiar odors regulate the acceptance of non-palatable, otherwise rejected, flavors; and that the route of transmission of the pre-exposed odor can be through air, or through food (amniotic fluid in previous studies and, in this case, breast milk), that is, via the retronasal and orthonasal routes.

Retronasal olfactory testing using candies sent by post and for screening purposes: a feasibility study.

The olfactory system is able to detect external odours through the orthonasal- and internal odours through the retronasal route. Flavour perception strongly relies on the sense of smell and this back route. In contrast to orthonasal, retronasal olfactory tests (ROT) are less frequently applied, although testing should be recommended for several reasons. The aim of the present investigation was to propose a suitable form of ROT for home-testing (and postal distribution) and evaluate a retronasal screening test. Initially, 111 participants were tested using a 27-item version of the Candy Smell Test (CST). Fifty-four participants performed retesting, of which 25 subjects did so in a home-setting being supplied with professionally packed "candy-chains". Seven candies were chosen by means of hit rate differences in normosmics and severely hyposmics/anosmics. The 7-CST is designed in a non-forced-choice fashion with same seven flavours to choose from. For the 27-item CST both groups (subjects performing home-testing and those performing retesting at the clinic) showed highly significant test-rest-reliabilities. The 7-CST was capable of discriminating healthy from diseased subjects when being tested in 116 healthy subjects and 47 patients suffering from olfactory dysfunction. The CST is suitable for home-testing and postal distribution. The new 7-item CST can be valuable for rapidly revealing anosmics. These findings help in further standardizing ROT, may encourage rhinologists to more routinely evaluate retronasal olfactory abilities and pave the way for larger epidemiologic studies also in regard to food preferences and nutritional behaviour.

The Association between Taste and Olfaction Perception Due to Retronasal Route among Female College Students Exploring Food Preferences

The Association between Taste and Olfaction Perception Due to Retronasal Route among Female College Students Exploring Food Preferences

The potential for retronasally delivered olfactory stimuli to assess psychiatric conditions

Recent research has linked the ability to identify odours to parts of the brain that, when impaired, are associated with mental illness or disease. The link between impaired odour perception and some psychological disorders has led to the suggestion that standardised assessments probing smell be routinely adopted in the clinical environment. Odour tests currently on the market utilise the orthonasal route, though the retronasal route is a viable, but overlooked, alternative. In this study, a flavour delivery system has been developed which quickly dissolves in the buccal cavity, rapidly releasing flavours that reach the olfactory system by the retronasal route. We tested seven different types of retronasal flavour stimuli (peppermint, aniseed, liquorice, coffee, orange, lemon, and valeric acid) on 171 undergraduate and postgraduate university students and related perceptual measures with psychological wellbeing scores. Olfactory measures included odour identification, pleasantness, intensity, and familiarity. Psychological measures of schizotypy (SPQ-B), depression, stress and anxiety (DASS-21), and autism spectrum disorder (RAADS-R) were obtained to represent psychological wellbeing. A battery of hierarchical multiple linear regressions were run to determine the relationships between odour perception and the psychometric measures. After controlling for age and gender, significant negative associations were found between odour identification and the stress (β = −.347, p < .001), anxiety (β = −.376, p < .001), depression (β = −.318, p < .001), schizotypy (β = −.473, p < .001), and RAADS-R (β = −.285, p < .001) scales. Additionally, both overall pleasantness (β = −.203, p < .01) and intensity (β = .194, p < .05) ratings were negatively correlated to the RAADS-R. Our findings indicate that retronasal stimuli present a feasible alternative to olfactory assessment of psychological states and further reinforces evidence indicating a correlation between olfactory and psychological measures.

The Feasibility of Gelatin-Based Retronasal Stimuli to Assess Olfactory Perception

Links between some psychological disorders and olfactory deficits are well documented, and screening tests have been developed to exploit these associations. Odors can take one of two routes to the olfactory receptors in the nasal epithelium, the orthonasal or retronasal route. This article discusses the potential use of the retronasal route to assess olfaction using gelatin-based stimuli delivered orally. Using a relatively new psychophysical method, the Single-Interval Adjustment Matrix task, we estimated vanillin thresholds for five healthy participants sampling small vanillin flavored gels. Our data demonstrate the feasibility of using solid-state gustatory stimuli to assess retronasal perception.

Olfactory dysfunction and its measurement in the clinic.

The sense of smell is largely taken for granted by laypersons and medical professionals alike. Indeed, its role in determining the flavor of foods and beverages, as well as in warning of, or protecting against, environmental hazards, often goes unrecognized. This is exemplified, in part, by the fact that most patients presenting to medical clinics with “taste” problems are typically subjected to complex brain imaging and gastroenterological tests without the sense of smell even being tested or considered as a basis of the problem. Aside from frank deficiencies in sweet, sour, bitter, salty and savory (umami) sensations, “taste” disorders most commonly reflect inadequate stimulation of the olfactory receptors via the retronasal route; i.e., from volatiles passing to the receptors from the oral cavity through the nasal pharynx. This article describes the two most common procedures for measuring the sense of smell in the clinic and provides examples of the application of these tests to diseases and other disorders frequently associated with smell loss. Basic issues related to olfactory testing and evaluation are addressed. It is pointed out that smell loss, particularly in later life, can be a harbinger for not only a range of neurodegenerative diseases, but can be a prognostic indicator of early mortality.

Oral texture influences the neural processing of ortho- and retronasal odors in humans

Eating implies mutual interactions between different senses. In the present work we aimed at studying relations between food texture and food odor, using both psychophysical and imaging techniques.Eighteen right-handed healthy human subjects participated to both behavioral and fMRI sessions. Fresh, sweetened milk and a more thickened version were delivered orally; in addition, a buttery-cream aroma was presented ortho- or retronasally. Stimuli were applied using a gustometer and or an air-dilution olfactometer, both computer-controlled. In each session subjects rated separately odor-, taste- and thickness intensities of the stimuli.The behavioral data show that odors, presented through either retro- or orthonasal path, induce a significant flavor enhancement with respect to the no-odor condition. Brain functional data indicated a significant enhancement of the activation of olfactory eloquent areas in favor of ortho-nasal odor presentation while activations of mechanosensory areas were favored by the retro-nasal odor route. As effect of oral stimuli we found a significant correlation between the texture intensity rating vs. the BOLD signal in the supplementary motor area, known to drive subconsciously primed movement, putatively associated in this case with the tongue movement required with the handling of the stimulus. Moreover, we found inhibition of the signal in different sensory specific areas as an effect of the mutual interaction between stimulus qualities.In conclusion, ortho- and retronasal odors differentially affect the neural processing of the texture of oral stimuli.

Grade 4 tonsillar hypertrophy associated with decreased retronasal olfactory function: a pilot study

Tonsillar hypertrophy is common in children, but it can also be present in adults. Enlarged tonsils, a significant anatomical barrier, may affect the flow of odor molecules from the oral cavity to the nasal passages, which has not yet been studied. Thus, we aimed to investigate the mass effect of palatine tonsillar hypertrophy on retronasal olfaction. This study was carried out in 146 subjects, with a mean age of 22.1 ± 2.2 years, ranging 20-29 years. An oropharyngeal examination of the participants was completed, and tonsillar hypertrophy was graded according to the subjective tonsil size scale. The participants were divided into four groups according to their tonsil size grading; then, each subject's orthonasal olfactory and retronasal olfactory functions were assessed using "Sniffin' Sticks" and retronasal olfactory testing. There were no differences observed between the groups in terms of age, gender, cigarette smoking, or alcohol consumption. In addition, there was no difference between the groups in terms of "Sniffin' Sticks" subtests and TDI scores. It was determined that the retronasal olfactory scores of the participants with grade 4 tonsil size were significantly lower than the retronasal olfactory scores of the participants with grade 1 tonsil size. The current investigation demonstrates that grade 4 tonsillar hypertrophy has significant negative effects on the retronasal route of olfactory sensing, when compared with grade 1 tonsillar hypertrophy.

Retronasal Odor Representations in the Dorsal Olfactory Bulb of Rats

Animals perceive their olfactory environment not only from odors originating in the external world (orthonasal route) but also from odors released in the oral cavity while eating food (retronasal route). Retronasal olfaction is crucial for the perception of food flavor in humans. However, little is known about the retronasal stimulus coding in the brain. The most basic questions are if and how route affects the odor representations at the level of the olfactory bulb (OB), where odor quality codes originate. We used optical calcium imaging of presynaptic dorsal OB responses to odorants in anesthetized rats to ask whether the rat OB could be activated retronasally, and how these responses compare to orthonasal responses under similar conditions. We further investigated the effects of specific odorant properties on orthonasal versus retronasal response patterns. We found that at a physiologically relevant flow rate, retronasal odorants can effectively reach the olfactory receptor neurons, eliciting glomerular response patterns that grossly overlap with those of orthonasal responses, but differ from the orthonasal patterns in the response amplitude and temporal dynamics. Interestingly, such differences correlated well with specific odorant properties. Less volatile odorants yielded relatively smaller responses retronasally, but volatility did not affect relative temporal profiles. More polar odorants responded with relatively longer onset latency and time to peak retronasally, but polarity did not affect relative response magnitudes. These data provide insight into the early stages of retronasal stimulus coding and establish relationships between orthonasal and retronasal odor representations in the rat OB.

FOOD THAT SMELLS TOO GOOD TO EAT

DIETERS WILL BE delighted if food research under way in the Netherlands fulfills its promise. There, scientists have shown that manipulating food aroma can curb appetite. These findings could enable manufacturers to produce foods that help consumers stick to their diets. “You can smell aroma in two ways,” notes Rianne Ruijschop, who is leading the project at Nizo food research, a contract research company with headquarters in Ede. Aroma inhaled through the nose takes the so-called orthonasal pathway. Aroma is also released from the mouth into the nasal cavity during chewing and swallowing of food and drink; this pathway is known as the retronasal route. Aroma compounds delivered via these two different routes stimulate different sectors of the brain, Ruijschop says. The orthonasal route activates brain regions associated with wanting and anticipating food. The retronasal route activates areas in the brain that are linked to a sense of reward, leading to sensations such as ...

Expiration: The moment we experience retronasal olfaction in flavor

Respiration is essential for smell perception. Previously we found that 8–12-Hz cortical rhythms were phase-locked to inspiration onset during the presentation of odor stimuli; this is referred to as inspiration phase-locked alpha band oscillation (I-α). Generators of I-α estimated with a dipole fitting model were found in the piriform, the entorhinal cortex (ENT), the amygdala (AMG), the hippocampus (HI) and the orbitofrontal cortex (OFC). Such olfactory perception is said to occur via the orthonasal olfaction route. Another route is the retronasal olfaction route. In this study, we investigated the link between respiration phase and retronasal olfactory perception. Electroencephalograph (EEG) and respiratory flows (separately measured with mouth and nose) were simultaneously recorded during stimulation of subjects’ tongues with liquids of chocolate, sucrose and water. The percentage of subjects correctly identifying the chocolate taste was higher when subjects were asked to breathe through the nose than when they were breathing through the mouth. In the averaged EEGs triggered by the onset of expiration measured from the flow through the nose, a 8–12-Hz oscillation was observed. Generators of this potential were found in the left ENT, HI, AMG and OFC in the order of milliseconds after expiration onset. Perception of retronasal olfaction is dependent on expiration, and combining retronasal olfactory information with gustatory information and somatosensation enable us to identify flavors when drinking and feeding.

The sense of smell: contributions of orthonasal and retronasal perception applied to metallic flavor of drinking water

The human senses are important assessment tools that assist water industry with effective water quality and water security monitoring. Flavor perception is combination of taste and odor; odor perception is a combination of orthonasal and retronasal perception. Orthonasal perception is associated with the sniff and describes entry of odor molecules though nostrils to nasal cavity followed by interaction with odor receptor neurons. Retronasal perception describes mechanism in which odor molecules present in mouth are transported to back of nasopharynx and then to odor receptor neurons. Although both pathways bring odor molecules to olfactory epithelium where they are perceived and processed by brain, retronasal route is more important for humans in terms of detecting ingested odors. For copper (II), metallic flavour is a combination of a weak bitter taste and a strong metallic odor that is produced as a biochemical reaction in mouth. Copper (II) in presence of oxygen causes lipid oxidation of arachidonic, linoleic, and oleic acids in mouth. A more thorough understanding of sense of smell will greatly aid water industry in its quest to produce a palatable product.

Influence of simultaneous gustatory stimuli on orthonasal and retronasal olfaction

Orthonasal and retronasal olfaction processes differ. The aim of this study was to examine whether congruent and incongruent simultaneous gustatory stimuli influence orthonasal and retronasal odorant perception, using olfactory event-related potentials as a measure. Thirty-two young, healthy subjects (16 men, 16 women) took part in two test sessions. Olfactory event-related potentials were recorded in response to a food-like odor, vanillin, and to an odor usually not associated with foods, the rose-like phenylethylalcohol. Each session consisted of four randomized blocks of 15 stimuli each which were applied either orthonasally or retronasally. Simultaneously, sweet or sour gustatory stimuli were applied. In response to retronasal vanillin, stimuli latencies P2 of the event-related potentials were significantly shorter in the congruent “sweet condition” than the incongruent “sour condition”. In contrast, with orthonasal stimulation, shorter P2 latencies were seen for both odorants in the incongruent condition. Intensity of both odorants was perceived as less pronounced after retronasal stimulation than after orthonasal stimulation. In conclusion, application of a sweet taste significantly enhanced the processing of a congruent olfactory stimulus when presented through the retronasal route. Incongruent simultaneous gustatory stimulation applied during orthonasal olfaction seemed to induce conflict priming, also resulting in faster processing.

Temporal processing of olfactory stimuli during retronasal perception

Odorants can be perceived via the nose during an inhalation or sniff (orthonasal perception) and via the mouth, nasopharynx and nasal cavity during mastication or drinking (retronasal perception). Previous data suggest that orthonasal perception provides a more efficient route with greater difficulty being reported when detecting [Halpern BP. Retronasal and orthonasal smelling. Chemosense 2004;6:1–7; Voirol E, Daget N. Comparative study of nasal and retronasal olfactory perception. Lebensmittel-Wissenschaft Technol 1986;19:316–9] and identifying [Heilmann S, Hummel T. A new method for comparing orthonasal and retronasal olfaction. Behav Neurosci 2004;118:412–9; Sun BC, Halpern BP. Identification of air-phase retronasal and orthonasal odorant pairs. Chem Senses 2005;30:1–14] single odorants retronasally. Whether the poorer sensitivity obtained via the retronasal route is largely due to the greater adsorption of odorants by the nasopharyngeal mucus compared to the nasal mucus thereby reducing their peak concentration and/or slowing their passage, has not been resolved. Importantly, the question of whether solubility of odorants in mucus or water predicts the outcomes for perception of stimuli presented via the retronasal route has not been resolved. Accordingly, the present study investigates this question by determining whether the solubility of an odorant in mucus predicts which component of a binary odour mixture is perceived first during retronasal perception. The results indicate that solubility in mucus rather than solubility in water is a better predictor of which odour will be perceived first and identified more readily during the retronasal perception of a binary mixture. In addition, lower intensity levels of single odorants occurred via the retronasal route suggesting that adsorption was greater via this route. Whether this was due to nasopharyngeal mucus having a greater adsorptive area or different composition compared to the orthonasal pathway is not known.

A European study for the validation of a retronasal test of olfaction.

Event Abstract Back to Event A European study for the validation of a retronasal test of olfaction. Christos Merkonidis1*, Carl Philpott1, Mahmoud Salam1 and Thomas Hummel2 1 The Ipswich Hospital NHS Trust, United Kingdom 2 Dresden University Hospital, Smell and Taste Clinic, Germany There are various olfactory tests available for testing a patient’s sense of smell but these are essentially designed to test orthonasal olfaction. When eating food, however, it is retronasal olfaction that gives a person a sense of flavour. We present a study about the sense of smell via the retronasal route on both healthy and pathological subjects. This prospective study took place at The Ipswich Hospital and was part of a multicentre, pan-European study, which is conducted in order to validate this format of testing in a more ‘universal’ fashion. We included 28 patients (15 with no nasal disease and considered to have a normal sense of smell and 13 with active nasal pathology). All individuals were tested with 40 different odours in the form of powder, placed at the back of the tongue. In addition, all individuals had a validated orthonasal test in the form of the Sniffin Stick’s test. Olfactory disorders were due to inflammatory, infectious, idiopathic and congenital causes. There were significant differences between the healthy and pathological subjects (p<0.005) for both the orthonasal and retronasal tests. There was good correlation between the two tests in the group with nasal pathology (p<0.02). The powders most commonly incorrectly identified in both groups were cocoa, fish and almond. Retronasal testing in patients with olfactory disorders is proven to be an effective method in testing flavour perception. Conference: Summer School on Human Olfaction, Dresden, Germany, 19 Jul - 25 Jul, 2009. Presentation Type: Poster Presentation Topic: Abstracts Citation: Merkonidis C, Philpott C, Salam M and Hummel T (2009). A European study for the validation of a retronasal test of olfaction.. Conference Abstract: Summer School on Human Olfaction. doi: 10.3389/conf.neuro.09.2009.12.024 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Jul 2009; Published Online: 23 Jul 2009. * Correspondence: Christos Merkonidis, The Ipswich Hospital NHS Trust, Suffolk, United Kingdom, merkonidis@hotmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Christos Merkonidis Carl Philpott Mahmoud Salam Thomas Hummel Google Christos Merkonidis Carl Philpott Mahmoud Salam Thomas Hummel Google Scholar Christos Merkonidis Carl Philpott Mahmoud Salam Thomas Hummel PubMed Christos Merkonidis Carl Philpott Mahmoud Salam Thomas Hummel Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Ortho- and Retronasal Presentation of Olfactory Stimuli Modulates Odor Percepts

Retronasal olfaction gives us information important not only for the well-being by detecting dangerous substances but also provides a basis for the pleasures of eating and drinking. However, odors presented via the retronasal route appear to evoke different sensations compared to orthonasal presentation. In this study, we differentially stimulated anterior and posterior parts of the subjects’ nasal cavity with odors. Subjects were able to tell retronasal and orthonasal smelling apart; the ability of doing so seemed to be linked to but could not completely be explained by the degree to which the odorant stimulated the trigeminal nerve. Furthermore, we examined whether food and nonfood odors were perceived as differently pleasant, depending on the presentation site. In fact, some but not all nonfood odors were described as less pleasant when they were delivered retronasally. In conclusion, the present results clearly suggest that there are differences between sensations produced by presenting odors through the retronasal or the orthonasal route, which bears significance for both basic and applied research.