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PubMed1999

Role of olfaction in food preference as evaluated in an animal model.

Food preference in individual animals is regulated by brain activity. Two murine model systems for investigating food preference were developed by focusing on fruit juices. In a home-cage, two-bottle test, the volume of apple juice consumed was found to be much larger than that of orange juice. In a two-nozzle "Drinkometer" test, by which each mouse was kept in a 38 cm (W) x 32 cm (D) cage and each drinking event was recorded by an electronic "Drinkometer" device, it was again found that the mice preferred drinking apple juice to orange juice. To elucidate the role of olfaction in this food preference, mice were subjected to an olfactory bulbectomy to remove the olfaction capability. In the home-cage two-bottle test, the preference for apple juice over orange juice was apparent even after the olfactory bulbectomy, indicating that olfaction was not essential for the formation of food preference behavior. In contrast, in the two-nozzle "Drinkometer" test, the preference for apple juice over orange juice was found to be abrogated by this surgery, implying the involvement of olfaction-based memory on food preference behavior.

Animals↗
PubMed1984

Impairment of taste and olfaction in patients with cirrhosis: the role of vitamin A.

Taste and olfaction sensory modalities and the response to vitamin A replenishment were studied in 37 vitamin A deficient patients (determined by low serum levels and abnormal dark adaptation) with stable alcoholic cirrhosis. Among this group of patients, 11 also had low serum zinc levels which ranged from 45 to 63 micrograms/dl. Initial taste and olfaction mean detection thresholds for all test substances were significantly higher (less sensitive) in all patients as compared to 21 sex-matched healthy subjects of the same age range (P less than 0.05). Twenty-seven patients including the 11 patients with low serum zinc were treated with oral vitamin A (10 000 micrograms/d) for 4 weeks. Among the vitamin a deficient patients there was significant improvement following vitamin A treatment in the mean detection and mean recognition thresholds for bitter and salty taste (P less than 0.01) and for pyridine olfaction (P less than 0.05) regardless of zinc status. Improvement in taste and olfaction correlated with a reversal of serum vitamin A levels and dark adaptation toward normal. The mechanism whereby vitamin A affects specific taste and smell (ie salty and bitter taste; pyridine smell) modalities is at present unknown.

Adult↗
PubMed2006

An updated review of clinical olfaction.

PURPOSE OF REVIEW: Disorders of the sense of smell can result through hundreds of different processes, but most commonly occur from upper-respiratory-tract infections, trauma, and chronic rhinosinusitis. RECENT DEVELOPMENTS: Research in the basic science of olfaction has progressed rapidly with powerful new molecular discoveries; however, our ability to treat these disorders remains limited. In clinical olfaction we are just realizing the broader existence of the sensory dysfunction in our population. We are discovering associations between neurodegenerative disorders and smell function that may allow us to identify these disorders earlier in the disease process. We are also challenging our previous categorization schemes and realizing that many etiologies cross the traditional conductive and neuro-sensory divisions. SUMMARY: Currently, aside from the possible therapeutic potential of systemic steroids, we have no effective treatment for the most common causes of olfactory loss. Recent advances in the basic science of olfaction provides us with an opportunity to develop new and novel clinical studies in an attempt at improving the quality of life for many of these patients.

Brain Injuries↗
PubMedDate not supplied

Recovery of nasal physiology after functional endoscopic sinus surgery: olfaction and mucociliary transport.

We assessed the changes in olfaction and mucociliary transport after functional endoscopic sinus surgery (FESS) in 80 patients with chronic paranasal sinusitis. Olfaction was evaluated with the butanol threshold test and mucociliary transport was assessed by saccharin transit time (STT). Postoperative butanol threshold scores were significantly reduced (p < 0.01), and the changes were more profound in severer forms of paranasal sinusitis as graded by ostiomeatal-unit computed tomography. The mean preoperative STT (27 min) which was significantly longer than that of controls (12 min) was significantly reduced 1, 6 and 12 months following FESS (p < 0.01). The results suggest that impairment of olfaction and mucociliary transport in chronic paranasal sinusitis may be significantly improved following FESS.

Adult↗
PubMed1999

Smell diskettes as screening test of olfaction.

A screening test of olfaction was developed with reusable diskettes as applicators of 8 different odorants. Using a questionnaire with illustrations, the test was designed as a triple forced multiple choice test resulting in a score of 0 to 8 correct answers. To validate the test, 102 volunteers with normal olfaction, as well as 22 patients with subjective hyposmia or anosmia, were tested. To compare the developed test with an already validated method, the same persons also performed the sniffin' sticks screening test. The results indicate that the screening test with smell diskettes recognizes patients with normal olfaction and consistently distinguishes them from patients with hyposmia or anosmia.

Adolescent↗
PubMed1987

[Assessing olfaction in general practice. A study of suitable odors].

We tested 15 substances, some of which have not so far been used for olfactometry, on a group of 200 normal adults and on 50 patients with impairment of olfaction. In the first stage the test substances were offered on strips of blotting paper. With this qualitative procedure 6 substances were found to be typical and well recognized. In a second stage these substances were tested quantitatively using the Elsberg olfactometer. This series revealed four groups with gradually differing olfactive activity. From each group one substance was accepted for definitive testing. These were: peppermint oil (strongest olfactory stimulus), benzaldehyde, orange oil and eugenol (weakest stimulus). Using this olfactory scale in the blotting paper test a rough quantitative screening of the degree of olfaction impairment should be possible, without recourse to expensive olfactometry.

Humans↗
PubMed2000

You can teach an old dog new tricks: olfaction and responses to novel foods by the elderly.

It can be difficult to document effects of age-related olfactory loss on eating behavior. However, we have reported that elders, especially those with poor olfaction, were more willing to accept novel foods than were younger adults. It was also found that elderly subjects were more willing to accept foods with unpleasant odors than were young subjects. Because there is often confounding between a food's odor pleasantness and its familiarity, the purpose of this study was to separate the effects of familiarity and odor pleasantness on food acceptance by the elderly. There was no evidence for effects of age or olfactory sensitivity on food neophobia. However, elderly subjects with poor olfaction showed less reluctance to try the unpleasantly smelling foods than did other subjects. These results suggest that increased willingness to try novel foods among elderly subjects with poor olfaction in earlier work was due to decreased rejection of foods with unpleasant odors and not due to decreased food neophobia per se.

Aged↗
PubMed2001

Attention to olfaction. A psychophysical investigation.

Olfaction is unique among the senses in that signals from the peripheral sensory receptors bypass the thalamus on their way to the cortex. The fact that olfactory stimuli are not gated by the thalamus has led some researchers to suggest that people may be unable to selectively direct their attention toward the olfactory modality. We examined this issue in an experiment where participants made speeded intensity (strong vs weak)-discrimination responses to an unpredictable sequence of olfactory and visual stimuli. Attention was directed to either olfaction or to vision by means of an informative cue that predicted the likely modality for the upcoming target on the majority of trials. Participants responded more rapidly when the target was presented in the expected rather than the unexpected modality, showing that people can selectively attend to olfaction.

Adult↗
PubMed2005

The relative importance of olfaction and vision in a diurnal and a nocturnal hawkmoth.

Nectar-feeding animals can use vision and olfaction to find rewarding flowers and different species may give different weight to the two sensory modalities. We have studied how a diurnal or nocturnal lifestyle affects the weight given to vision and olfaction. We tested naïve hawkmoths of two species in a wind tunnel, presenting an odour source and a visual stimulus. Although the two species belong to the same subfamily of sphingids, the Macroglossinae, their behaviour was quite different. The nocturnal Deilephila elpenor responded preferably to the odour while the diurnal Macroglossum stellatarum strongly favoured the visual stimulus. Since a nocturnal lifestyle is ancestral for sphingids, the diurnal species, M. stellatarum, has evolved from nocturnal moths that primarily used olfaction. During bright daylight visual cues may have became more important than odour.

Animals↗
PubMed2006

Structure-olfactive threshold relationships for pyrazine derivatives.

Structure-olfactive threshold relationships for 40 pyrazine derivatives have been studied by multivariate statistical analysis. Variable descriptors used to describe the molecules studied were obtained using molecular-mechanics software. A correlation coefficient of 0.82 was obtained when all the molecules were included in the model. When the model was established for closely related subsets of molecules, the correlation coefficients obtained were higher and the established models were bilinear. Such models allow the identification of optimal structures corresponding to low olfactive thresholds for the subsets studied. Surprisingly, we find that the optimum structures are included in the set of 40 molecules. The efficiency of the models was supported by the cross-validation technique, where the correlation coefficients were found to be good with respect to the precision of the values of the olfactive thresholds.

Pyrazines↗
PubMed1975

Olfaction in fish.

1. Recent progress in the studies on olfaction in fish, with particular emphasis on electrophysiological and behavioral responses to biological odors and related chemicals, is reviewed. 2. One of the most characteristic features in fish olfaction is that it takes place entirely in the aquatic environment. The carrier of stimulant molecules is not air but water; therefore, chemicals that are detected olfactorily by fish need not be volatile, but must be soluble in water. 3. The olfactory organs of fishes are diversely developed. At one extreme they are well developed (macrosmatic) such as in sharks and eels, and at the other they are poorly developed (microsmatic) such as in pike and stickleback. 4. The nasal cavity is lined with the olfactory epithelium, which is raised from the floor of the organ into a series of lamellae to make a rosette. The arrangement, shape and degree of development of the lamallae in the rosette vary considerably from species to species. 5. It is doubtful whether simple relation exists between the surface area of the olfactory epithelium and sensitivity to odors, since the sensory epithelium is not distributed uniformly over the surface of the olfactory lamellae. 6. The olfactory epithelium of fish, like other vertebrates, consists of three cell types: receptor cells, supporting cells and basal cells. 7. The receptor cell, which is a bipolar primary sensory cell, sends a slender cylindrical dendrite toward the surface of the epithelium and is directly connected with the olfactory bulb by its axon. The dendrite terminates in a minute swelling (olfactory knob) which bears a variable number of cilia. 8. The information from the receptor cell is conveyed into the olfactory bulb, the first relay station, where signals are processed and integrated. The dominant feature of the bulb is the synaptic contact between the primary and secondary olfactory neurones in the form of glomerulus. 9. All the available evidence points to a great acuity of the olfactory sense in many fish species both in the capability and discriminating odorous chemicals. However, much discrepancies exist among data obtained by behavioral and electrophysiological techniques mainly because of the lack of systematic investigations. 10. Electrophysiological studies of olfaction have been hampered by the extremely small size of the olfactory neurones. 11. A slow negative monophasic potential is induced in the olfactory epithelium when stimulated with odorous chemicals (electro-olfactogram, EOG).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Perireceptor and receptor events in vertebrate olfaction.

In this article we have summarized the basic information which identifies several key issues in the study of perireceptor and receptor events in vertebrate olfaction. We have emphasized the biophysical and biochemical data which have established a pivotal role for the olfactory mucus in the access of odorants to receptor sites as well as their clearance from the micro-environment. In addition, based on initial reports in the literature, we have postulated that the uptake of odorants by cells in the olfactory epithelium and their subsequent enzymatic degradation is an important mechanism in odorant removal. Hence, the pre- and post-interactive events in vertebrate olfaction play a key role in molecular recognition, sensory transduction and receptor desensitization. Study of the primary events in vertebrate olfaction is an increasingly active area of research in neurobiology. Application of contemporary techniques in cell and molecular biology as well as biochemistry and cellular biophysics is yielding new insights into the process and into establishing new hypotheses to be tested.

Animals↗
PubMed2004

Anesthesia affects olfaction and chemosensory event-related potentials.

OBJECTIVE: Olfactory and trigeminal systems interact and contribute to the perception of odorants. This study was aimed at investigating the effect of local anesthesia on olfaction. METHODS: One percent of tetracaine on a cotton swab was applied intranasally at three different locations in 20 volunteers and 4% of lidocaine was applied to the olfactory cleft in a head-down position. Before and after anesthesia, self-assessment, psychometric testing and olfactory event-related potentials [OERPs, using H(2)S and phenyl ethyl alcohol (PEA)], and chemosomatosensory event-related potentials (CSSERPs, using CO(2)) were examined. RESULTS: Anesthesia at all four locations significantly lowered the perceived self-assessment of olfaction, while using the cotton swab only anesthesia in the middle meatus elevated threshold (P = 0.020), lowered discrimination (P = 0.015), and prolonged OERP (PEA, P = 0.008; H(2)S, P = 0.016), as well as CSSERPs latencies (CO(2), P = 0.020). However, complete temporary anosmia was only achieved after applying 4% lidocaine into the olfactory cleft. CONCLUSIONS: Intranasal anesthesia applied with a swab reduced self-assessment of olfaction but was unable to produce anosmia. Psychometric test results were concordant with changes in chemosensory event-related potentials. SIGNIFICANCE: Temporary anosmia is technically difficult to achieve but could be demonstrated for the first time using local anesthesia. Even though anesthesia influences self-assessment, measurable olfactory function can remain unchanged.

Administration, Intranasal↗
PubMed2005

Humans as an animal model for systems-level organization of olfaction.

The past 15 years have seen significant advances in the study of olfaction, with particular emphasis on elucidating the molecular building blocks of the sensory process. However, much of the systems-level organization of olfaction remains unexplored. Here, we provide an overview at this level, highlighting results obtained from studying humans, whom we think provide an underutilized, yet critical, animal model for olfaction.

Animals↗
PubMed2002

Linking olfaction with nausea and vomiting of pregnancy, recurrent abortion, hyperemesis gravidarum, and migraine headache.

OBJECTIVE: The experience of women was sought about nausea and vomiting, its relation to olfaction, its occurrence among pregnant women with anosmia, and the potential association of hyperemesis gravidarum and migraine headache. METHODS: We performed a community-based study with a physician/patient-directed questionnaire, and a retrospective analysis of hospital records. RESULTS: Nearly all women (n = 163 parous women) experience nausea (98%) and vomiting (97%). The highest frequency causes of nausea and vomiting were "food poisoning" (65%), "flu" (58%), pregnancy (54%), and offensive odors (52%); vomiting occurred as frequently as nausea for the first 2 causes, and one half as often for the latter causes. Most women reported that the pain experienced during vomiting exceeded that of parturition. Among 9 women with hypogonadotropic anosmia with advanced reproductive technology-induced pregnancies, 2 experienced nausea and vomiting, one from "food poisoning." Among 37 women with migraine headache, 10 (27%) had experienced hyperemesis gravidarum, and among 16 who experienced hyperemesis gravidarum, 5 (37%) had migraine headaches. CONCLUSIONS: The frequency of nausea and vomiting, caused most often by nonpregnancy-related triggers, is high among women. In a small sample of women with congenital anosmia, nausea and vomiting of pregnancy occurred in only 1 pregnancy, suggesting that olfaction is a highly selected trigger for nausea and vomiting of pregnancy. The shared nausea and vomiting experience of hyperemesis gravidarum and migraine headache among women suggests a common mechanism, possibly based on allelic variations within the DRD2 (dopaminergic receptor) gene. Because olfactory receptors, odor types, and MHC antigens are closely integrated, and because olfactory stimuli often incite episodes of pregnancy, nausea, and vomiting, hyperemesis gravidarum, and migraine headache, these genes and their products invite further scrutiny. The pregnancy-conserving effect of PNV and the MHC antigen overlap in couples with recurrent abortion are important clues possibly relating olfaction, MHC antigens, and reproductive success or failure.

Abortion, Habitual↗
PubMedDate not supplied

Psychophysical methods in the study of olfaction and respiratory tract irritation.

This article describes the fundamentals of olfaction and irritation perception and the dominant psychophysical methods for the assessment of olfaction and respiratory tract irritation. It also discusses factors that determine the olfactory and irritant response (ranging from the physicochemical properties of the stimulus to the physiological and cognitive characteristics of the individual). Because the vast majority of volatile chemicals stimulate the olfactory system at concentrations well below that at which they will elicit trigeminal activation, the evaluation of irritation from volatiles is often confounded by the perception of odor. Several methods have been used for studying the perception of irritation, without the influence of olfaction. The perception and reports of acute adverse effects of odor, annoyance, and irritation from volatile chemicals have multiple determinants. Understanding the perceptual impact of chemicals under environmentally realistic conditions requires attending to both the sensory and the psychological impact of those exposures. The review, which is largely based on presentations given by Dr. Richard Doty and Dr. William Cain, concludes by discussing the importance of the psychophysical approach, which considers physiochemical, subject, experimental, and cognitive/ psychological factors, for research in the chemical senses.

Environmental Pollutants↗
PubMed1999

Effects of middle turbinate medialization on olfaction.

OBJECTIVE/HYPOTHESIS: Turbinate medialization techniques have gained popularity in an attempt to prevent turbinate lateralization. Theoretically, adhesions between the septum and middle turbinate will prevent lateralization but may compromise airflow to the olfactory neuroepithelium and affect the sense of smell. No studies have addressed this issue. The objective of this study is to evaluate effects of middle turbinate medialization on olfaction. STUDY DESIGN: A prospective controlled study of olfaction before and after middle turbinate medialization using the University of Pennsylvania Smell Identification Test (UP-SIT) and patient questionnaires. METHODS: Fifty patients underwent endoscopic sinus surgery (ESS) with middle turbinate medialization and preservation. The caudal end of the middle turbinate and the opposing septal mucosa were abraded with a microdebrider for iatrogenic synechia formation in an attempt to avoid lateralization of the middle turbinate. Each of the patients underwent preoperative assessment with a questionnaire and UPSIT. All patients were reevaluated approximately 5 weeks after surgery by endoscopic examination, questionnaire, and the UPSIT. The preoperative and postoperative questionnaire responses were compared for subjective analysis. Objectively, the preoperative and postoperative UPSIT scores were compared using the Student t test. RESULTS: The questionnaires showed that the study population's subjective sense of smell either did not change or improved compared with the preoperative state. Objectively, there was a mean increase of UPSIT scores after surgery. This difference was not statistically significant (P = .4). CONCLUSION: Middle turbinate medialization has no detectable adverse effect on olfaction.

Adult↗
PubMed2000

Taste(s) and olfaction(s) in fish: a review of specialized sub-systems and central integration.

Evidence from comparative morphology and electrophysiology suggests that both, olfaction and taste in fish serve different ecological roles. The lateral olfactory system (dorsolateral olfactory bulb glomeruli and lateral olfactory tract) and the external taste buds are probably specialized for food search and amino acid discrimination. The medial olfactory system (basomedial olfactory bulb glomeruli and medial olfactory tract) and the solitary chemosensory taste cells, however, may have their roles in intra- and interspecific interactions (discriminating pheromones by olfaction, bile components by both olfaction and taste). Whereas stimulation of the taste systems alone triggers reflexes, complex, conditional or conditioned behaviours are only released when the olfactory system is intact. This points at the importance of telencephalic and diencephalic integration of olfactory and taste inputs. Consequently, caution is appropriate concerning simplistic interpretations of deprivation experiments.

Animals↗