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PubMed2007

Dissociated representations of irritation and valence in human primary olfactory cortex.

Irritation and negative valence are closely associated in perception. However, these perceptual aspects can be dissociated in olfaction where irritation can accompany both pleasant and unpleasant odorants. Whereas the sensation of odor reflects transduction at olfactory receptors, irritation reflects concurrent transduction of the odorant at trigeminal receptors. Thus a stimulus can be either a pure olfactant activating the olfactory receptors only or a bimodal odorant activating both types of receptors. Using event-related functional magnetic resonance imaging and a 2 x 2 experimental design contrasting odorant valence (pleasant/unpleasant) and odorant type (pure olfactant/bimodal) we found activity in piriform cortex to be associated with valence, and not type, of odors. In contrast, activity in the olfactory tubercle was associated with type, and not valence, of odors. Importantly, this was found when perceived intensity was held equal across odorants. These findings suggest that dissociable neural substrates subserve the encoding of irritation and valence in olfaction.

Adult↗
PubMed1981

[Occupational impairment of the olfactory sense of chromate producing workers (author's transl)].

Using T & T Olfactometer which had been developed and standardized for clinical use in Japan recently, measurements of olfactory thresholds of odor detection and of odor recognition were carried out on 33 subjects (26 males and 7 females), who had worked in a chromate producing factory. The subjects had left the factory before 7 years or more. Five kinds of test odors were used; beta-phenyl ethyl alcohol, methyl cyclopentenolone, iso-valeric acid, gamma-undecalactone, and scatol. The degree of olfaction loss was expressed with the number of powers of 10 in series of multiple concentrations by 10 of each test odor with reference to the concentration of the detection threshold of young normal people. Seventeen of 33 subjects (51.4%) had a perforation of the nasal septum. Middle and high grade decrease of odor recognition faculty were found in 18 (54.5%) including 2 anosmia, one of whom complained also of the disorder of taste. Any specific pattern of olfactogram characterizing them were not found, namely, chromates impair olfactory sense for all kinds of odors, which means the impairment of olfactory epithelium itself. The degree of olfaction loss was related to the duration of employment in the chromate producing factory. The existence of septal perforation had no direct relation to the degree of olfaction loss.

Adult↗
PubMed2006

Olfactory disorder in children with 22q11 deletion syndrome.

OBJECTIVE: 22q11 deletion syndrome, a common human interstitial deletion syndrome (1:5000), is associated with a heterogeneous physical phenotype, including several factors that markedly increase the risk for olfactory disorder. Despite its potential consequences, pediatric studies of impaired olfaction are rare, and odor detection in children with 22q11 deletion syndrome has not yet been examined. METHODS: The University of Pennsylvania Smell Identification Test was administered to 62 children, including 39 with 22q11 deletion syndrome and 23 neurotypical control siblings who ranged in age from 5.3 to 14.8 years. Lowered smell detection accuracy among affected children was predicted. RESULTS: Substantially more children with 22q11 deletion syndrome (68%) as compared with neurotypical control subjects (13%) had University of Pennsylvania Smell Identification Test scores > or = 2 SDs below the standardization sample mean. Frequency of impairment in younger versus older children did not differ. The score distributions of children with and without velopharyngeal insufficiency did not differ; however, markedly lower score variance among children with velopharyngeal insufficiency suggested its negative impact on olfaction. Posthoc error analyses revealed that affected children had special difficulty detecting smells that are associated with fumes and smoke. CONCLUSIONS: Odor detection failures are ubiquitous among children with 22q11 deletion syndrome and are not associated with developmental delay or performance characteristics of younger affected children. Additional studies are needed to examine further the impact on olfaction of velopharyngeal insufficiency and compromised nasal airway patency. Children with 22q11 deletion syndrome should be evaluated routinely for olfactory disorder. When deficits are identified, caregivers should be warned of potential dangers that are associated with this type of sensory impairment.

Adolescent↗
PubMed1995

Anosmia following head trauma: preliminary study of steroid treatment.

Twenty patients with post-traumatic anosmia were subjected to olfactory function testing, including olfactory acuity tests using a T & T olfactometer and an intravenous olfaction test. T & T tests revealed complete loss in 14 patients. In the intravenous olfaction test, 14 patients showed no response and 5 patients showed abnormal responses. The severity of olfactory dysfunction showed no correlation with background factors such as the site of head trauma, the presence of the fracture of skull, the presence of unconsciousness, or the presence of head operation. As a preliminary study, seventeen patients were administered a corticosteroid, a topical nasal drop of 0.1% betamethasone for 12 patients and an oral administration of prednisolone for 5 patients. Four patients showed slight recovery of olfactory function following a corticosteroid therapy. Effects of corticosteroids on olfaction might be explained by regeneration of olfactory receptor cell axons and reestablishment of contact with cells in the olfactory bulb.

Adrenal Cortex Hormones↗
PubMed1995

[Improvement of olfactory disturbance by endoscopic endonasal surgery for chronic sinusitis].

Olfactory disturbance is the one of the most important symptoms of chronic sinusitis. In the present study, we followed up the postoperative clinical course of olfactory disturbance in patients who underwent surgery for chronic sinusitis. Ninety patients with severe olfactory disturbance or anosmia who underwent endoscopic endonasal surgery for chronic sinusitis with severe olfactory disturbance or anosmia in the preceding three-year period were enrolled in this study. We obtained a high postoperative improvement rate of 78.8%. We compared and examined our cases' postoperative clinical course concerning their olfactory disturbance and various factors in other patients before and after surgery, and obtained the following results: a) Young patients, 30 years old or under at the time of surgery, showed significantly higher rates of improvement than patients who were 50 years old or more at the time of surgery. b) Even though revision surgery was performed, the improvement rates were almost the same as after the initial surgery. c) Although the Alinamin intravenous olfaction test is regarded as an olfaction threshold test, we have seen quite a few cases in which improvement was achieved despite the absence of a preoperative response to the Alinamin intravenous olfaction test. d) There was no clear correlation between the presence of preoperative lesions of the ethmoid sinus and the olfactory cleft and the improvement rates. e) The cases with unsatisfactory results concerning the paranasal sinuses and nasal cavity--those accompanied by postoperative adhesions of the olfactory cleft, recurrence of polyps, etc.,--showed significantly lower improvement rates than cases with satisfactory postoperative results. During surgery in patients with severe olfactory disturbance, we conclude that it is particularly important to adequately clean the lesions of the olfactory cleft and the anterior and posterior ethmoid sinus endoscopically. This ensures leaving clear the olfactory cleft.

Adult↗
PubMed1998

Olfactory disorders induced by cadmium exposure: a clinical study.

The evaluation of olfaction is not only widely applied and undeniably valuable in clinical diagnostics but it is also of interest to industrial medicine. It should be borne in mind that in certain workplaces, particularly in the chemical industry, the olfactory receptor has to act as an organ which warns the worker against threatening intoxication, and this is possible only when it functions properly. Cadmium, as a highly toxic metal, found widely in industry and in the environment, is frequently included in the list of chemicals known to cause olfactory impairment. The purpose of this study was to evaluate olfaction in workers occupationally exposed to cadmium. The correlation between olfaction and concentrations of cadmium in urine, blood and in the workplace air as well as employment duration was examined in workers of the "CENTRA" S.A., an electrochemical plant in Poznań. In this plant cadmium-nickel batteries are produced, and there is chronic occupational exposure to cadmium in quantities exceeding maximum allowable concentration (MAC). A group of 73 workers aged 20 to 60 years (42.0 +/- 18.0), employed from 4 to 24 years (12.5 +/- 8.5) were examined. Of the 73 workers who completed the evaluation, 53 people (72.7%) were smokers (10-40 cigarettes per day). In addition to medical history, medical and ENT examinations, blood and urine tests were taken and olfactometry performed. Olfactometry was performed according to Elsberg and Levy's method, modified by Pruszewicz, in which natural coffee as well as aniseed, lemon and mint oils were used. The quantitative and qualitative olfactory disorders were evaluated on the basis of the established odor detection threshold (ODT) and odor identification threshold (OIT). The examinations revealed numerous cases of hyposmia (26.0%) and parosmia (17.8%) and one case of anosmia (1.4%). In the majority of people with olfactory disorders, hypertrophic changes in the nasal mucosa, dependent on the duration of employment, were identified. Statistically significant relationship between olfactory impairment and cadmium concentration in blood, urine and the workplace air was observed. However, such a relationship was not found in regard to the duration of employment. The study indicated the need to carry out routine olfactometries. The results of these examinations could be the ground to perform certain preventive and therapeutic procedures.

Adult↗
PubMed2006

Accessory chemosignaling mechanisms in primates.

Accessory olfaction is defined as the chemoreceptive system that employs the vomeronasal complex (VNC) and its distinct central projections to the accessory olfactory bulb (AOB) and limbic/cortical systems. Comparisons of the structural and functional features of primate accessory olfaction can now be made at many levels. Advances in the understanding of molecular mechanisms of odorant transfer and detection, physiological analyses of signal processing, and appreciation of ontogenetic timetables have clarified the contribution of accessory chemoreception to the sensory map. Two principal functions dominate: the decoding of social information through the uptake of signals (often fluid-borne), and the provision of an essential pathway for the "migration" of presumptive neurocrine (GnRH) cells from the olfactory placode to the hypothalamus. VN "smelling" (vomerolfaction) is now seen to overlap with primary olfaction. Both systems detect signal compounds along the spectrum of volatility/molecular weight, and neither is an exclusive sensor. Both main and accessory chemoreception seem to require collaborative molecular devices to assist in odorant transfer (binding proteins) and (for the VNO) signal recognition (MHC1 proteins). Most adaptive-selective features of primate chemocommunication variously resemble those of other terrestrial mammals. VN function, along with its genome, has been maintained within the Strepsirrhines and tarsiers, reduced in Platyrrhines, and nearly extinguished at the Catarrhine up to hominin levels. It persists as an intriguing ancient sense that retains key features of past evolutionary events.

Animals↗
PubMed2003

Genomics spawns novel approaches to mosquito control.

In spite of advances in medicine and public health, malaria and other mosquito-borne diseases are on the rise worldwide. Although vaccines, genetically modified mosquitoes and safer insecticides are under development, herein we examine a promising new approach to malaria control through better repellents. Current repellents, usually based on DEET, inhibit host finding by impeding insect olfaction, but have significant drawbacks. We discuss how comparative genomics, using data from the Anopheles genome project, allows the rapid identification of members of three protein classes critical to insect olfaction: odorant-binding proteins, G-protein-coupled receptors, and odorant-degrading enzymes. A rational design approach similar to that used by the pharmaceutical industry for drug development can then be applied to the development of products that interfere with mosquito olfaction. Such products have the potential to provide more complete, safer and longer lasting protection than conventional repellents, preventing disease transmission by interrupting the parasite life cycle.

Animals↗
PubMed2005

3D atlas describing the ontogenic evolution of the primary olfactory projections in the olfactory bulb of Xenopus laevis.

The adult Xenopus presents the unique capability to smell odors both in water and air thanks to two different olfactory pathways. Nevertheless, the tadpole can initially perceive only water-borne odorants, as the olfactory receptor neurons (ORN) that will detect air-borne odorants develop later. Such a phenomenon requires major reorganization processes. Here we focused on the precise description of the neuroanatomical modifications occurring in the olfactory bulb (OB) of the tadpole throughout metamorphosis. Using both carbocyanine dyes and lectin staining, we investigated the evolution of ORN projection patterns into the OB from Stages 47 to 66, thus covering the period of time when all the modifications take place. Although our results confirm previous works (Reiss and Burd [1997] Semin Cell Dev Biol 8:171-179), we showed for the first time that the main olfactory bulb (MOB) is subdivided into seven zones at Stage 47 plus the accessory olfactory bulb (AOB). These seven zones receive fibers dedicated to aquatic olfaction ("aquatic fibers") and are conserved until Stage 66. At Stage 48 the first fibers dedicated to the aerial olfaction constitute a new dorsomedial zone that grows steadily, pushing the seven original zones ventrolaterally. Only the part of the OB receiving aquatic fibers is fragmented, reminiscent of the organization described in fish. This raises the question of whether such an organization in zones constitutes a plesiomorphy or is linked to aquatic olfaction. We generated a 3D atlas at several stages which are representative of the reorganization process. This will be a useful tool for future studies of development and function.

Animals↗
PubMed1975

[Physiology of smell and taste].

The functional organization of olfaction and taste are briefly discussed in morphological, physiological, biochemical and behavioural terms. Olfaction in animals serves often for long range navigational purposes whereas taste acts as a close up "last moment food checking system". Special attention is given to the coding problems in both systems. In taste, the spatial coding mode is prevalent. In olfaction a very complex coding system exists, which used temporal as well as spatial means and in which a whole set of olfactory nerve fibers is activated during the transmission of any specific odor information, each fiber of the set discharging at a specific impulse pattern. The role of the olfactory bulb is seen as an integrating center with the capabilities for short and long term information storage. The impact of von Békésy's microstimulation experiments on the physiology of taste is discussed. Research on taste modifiers such as gymnemic acid or of the taste modifying protein "miraculin" enrich our present understanding of the interaction between taste stimulants and the chemoreceptor sites in the taste buds.

Animals↗
PubMed2006

Olfactory groove meningiomas: functional outcome in a series treated microsurgically.

BACKGROUND: A systematic investigation of long-term follow-up results after microsurgical treatment of patients harbouring an olfactory groove meningioma, particularly with regard to postoperative olfactory and mental function, has rarely been performed. We reassessed a series of patients treated microsurgically for an olfactory groove meningioma in regard to clinical presentation, surgical approaches and long-term functional outcome. METHOD: Clinical, radiological and surgical data in a consecutive series of 56 patients suffering from olfactory groove meningioma were retrospectively reviewed. FINDINGS: Presenting symptoms of the 41 women and 15 men (mean age 51 years) were mental changes in 39.3%, visual impairment in 16.1% and anosmia in 14.3% of the patients. Preoperative neurological examination revealed deficits in olfaction in 71.7%, mental disturbances in 55.4% and reduced vision in 21.4% of the cases. The tumour was resected via a bifrontal craniotomy in 36, a pterional route in 13, a unilateral frontal approach in 4 and via a supraorbital approach in 3 patients. Extent of tumour resection according to Simpson's classification system was grade I in 42.9% and grade II in 57.1% of the cases. After a mean follow-up period of 5.6 years (range 1-13 years) by clinical examination and magnetic resonance imaging (MRI), 86.8% of the patients resumed normal life activity. Olfaction was preserved in 24.4% of patients in whom pre- and postoperative data were available. Mental and visual disturbances improved in 88 and 83.3% of cases, respectively. Five recurrences (8.9%) were observed and had to be reoperated. CONCLUSIONS: Frontal approaches allowed better resection of tumours with gross infiltration of the anterior cranial base, tumours extending into the ethmoids or nasal cavity and in cases with deep olfactory grooves. Preservation of olfaction should be attempted in patients with normal or reduced smelling preoperatively.

Adult↗
PubMed1999

The extended transbasal approach: clinical applications and complications.

OBJECTIVES: To describe in detail key technical aspects of the extended transbasal approach which involves en-bloc mobilisation of the supraorbital rim, the orbital roof and the nasoethmoidal complex. In some patients osteotomies were performed around the cribriform plate with a view to maintaining olfaction. To review 18 patients with deep seated lesions located in the central skull base region (including 6 recurrences) to highlight patient selection, presentation, surgical morbidity and outcome. METHODS: Prospective data recording and clinical chart review. RESULTS: Outcome was assessed at a minimum of 1 year after operation using the Glasgow Outcome Score. Thirteen patients had made a good recovery, 1 was moderately disabled, 2 were severely disabled (both had been severely disabled before operation), and 2 died. By contrast, quality of life assessment indicated that only 7 of the surviving 14 adults had returned to normal levels of activity and perceived health; although 6 of the other 7 patients had resumed their former occupations, their follow up assessments showed a reduced quality of life. Of the 13 patients who had an olfaction preservation procedure, 6 showed appreciation of smell on formal testing. CONCLUSIONS: In patients with progressive and extensive deep seated lesions this technique provides wide exposure in a shallow surgical field. Complication rates although acceptable were significantly higher in patients with intradural lesions. In some selected patients it was possible to preserve olfaction. Specific surgical outcome assessments pointed to satisfactory results, but failed to reflect the degree of patient disability. There is a need for outcome measures that take into account the patient's expectations and which address his quality of life in order to validate the benefits of these procedures.

Adolescent↗
PubMed2007

The reach-to-grasp-food task for rats: a rare case of modularity in animal behavior?

Humans and non-human animals make use of sensory hierarchies in "selecting" strategies for solving many cognitive and behavioral tasks. Often, if a preferred type of sensory information is unavailable or is not useful for solving a given task, the animal can switch to a lower-priority strategy, making use of a different class of sensory information. In the case of rats performing a classic reach-to-grasp-food task, however, prior studies indicate that the reaching maneuver may be a fixed action pattern that is guided exclusively by the food's odor plume until the point of contact with the food morsel [Whishaw IQ, Tomie JA. Olfaction directs skilled forelimb reaching in the rat. Behav Brain Res 1989;32(1):11-21; Metz GA, Whishaw IQ. Skilled reaching an action pattern: stability in rat (Rattus norvegicus) grasping movements as a function of changing food pellet size. Behav Brain Res 2000;116(2):111-22; Whishaw IQ. Did a change in sensory control of skilled movements stimulate the evolution of the primate frontal cortex? Behav Brain Res 2003;146(1/2):31-41]. We sought to confirm and extend these findings in several ways. In Experiment 1, using a GO/NO-GO variant of the classic task, we demonstrated that rats used the GO target's odor both to trigger and guide their reaches. In Experiment 2, we showed that rats deprived of (a) vision, (b) object-recognizing rostral whiskers and forearm sinus hairs, or (c) both, displayed no deficits in triggering and guiding their reaches. Finally, in a third experiment in which the GO target's location varied randomly across trials and only olfactory cues were available, we demonstrated that rats could determine the spatial endpoint of their reach without any loss of accuracy. Combined with results from a prior study in which bulbectomized rats never developed a new, successful reaching strategy despite extensive post-operative training [Whishaw IQ, Tomie JA. Olfaction directs skilled forelimb reaching in the rat. Behav Brain Res 1989;32(1):11-21], these results indicate that rats do not have a sensory hierarchy for solving the reach-to-grasp-food task, but rather, are guided by olfaction alone until their paw contacts the food morsel.

Animals↗
PubMed2005

Use of ultrasonic vocalizations to assess olfactory detection in mouse pups treated with 3-methylindole.

Altricial mammals use olfaction long before the olfactory bulb has reached its anatomically mature state. Indeed, while audition and vision are still not functional, the olfactory system of newborn animals can clearly process distinct odorant molecules. Although several previous studies have emphasized the important role that olfaction plays in early critical functions, it has been difficult to develop a sensitive and reliable test to precisely quantify olfactory ability in pups. One difficulty in determining early sensory capabilities is the rather limited behavioral repertory of neonates. The present study examines the use of ultrasonic vocalizations emitted by isolated rodent pups as a potential index of odor detection in newborn mice. As early as postnatal day 2, mice reliably decrease their emission of ultrasonic calls in response to odor exposure to the bedding of adult male mice but not in response to clean bedding odors or to non-social odorant molecules. A toxin known to damage the olfactory epithelium in adult, the 3-methylindole, impairs the ultrasonic call responses triggered by exposure to male bedding, thus confirming the efficiency of this olfactotoxin on mice pups. The administration of 3-methylindole severely reduced the life expectancy of the majority of subjects. This result is discussed according to the critical role of olfaction in nipple-seeking behavior in mouse pups.

Animals↗
PubMed2006

Odour fingerprint acquisition by means of comprehensive two-dimensional gas chromatography-olfactometry and comprehensive two-dimensional gas chromatography/mass spectrometry.

The analysis of complex matrices, such as perfumes, by means of gas chromatography-olfactometry (GC-O) can be rather imprecise due to the co-elutions, leading to a possible masking of odour-active trace-level compounds by major interferences or agglomeration of olfactive impressions resulting in unreliable olfactive characterization. To overcome these limits an innovative technique, comprehensive two-dimensional gas chromatography-olfactometry (GC x GC-O), was applied, revealing several relevant co-elutions, as in the linalool and linalyl acetate zones. A total of 177 compounds, out of these 135 odour-active, were detected by GC-O, while about 481 out of 818 compounds presented odour-activity through GC x GC-O analyses. In addition, GC/mass spectrometry (GC/MS) and GC x GC/MS analyses were also performed. Peak assignment was achieved by means of different information sources, such as GC/MS, GC x GC/MS, LRI, injection of standards and olfactive impressions.

Chromatography, Gas↗
PubMed2007

Sildenafil affects olfactory function.

PURPOSE: Sildenafil is the first member of a new class of oral drugs effective for erectile dysfunction. However, approximately 20% of patients complain about nasal congestion after sildenafil administration. MATERIALS AND METHODS: Because nasal airflow and olfaction are closely linked, the sense of smell was evaluated in 20 young, healthy volunteers after the administration of 50 and 100 mg sildenafil, and placebo in a double-blinded, crossover study. Olfactory function was evaluated using a standardized and validated test (Sniffin' Sticks). To investigate a possible impact of G-protein beta3 subunit C825T polymorphism on the effect of sildenafil on olfaction the genotype of all subjects was determined. RESULTS: The effect of sildenafil on olfaction was only present at a dose of 100 mg but not at a dose of 50 mg sildenafil. The genotypes TT, CC and TC of the G-protein beta3 C825T polymorphism had no impact on the change in olfactory function. CONCLUSIONS: Higher sildenafil doses may produce decreased olfactory sensitivity.

Cross-Over Studies↗
PubMed2003

The fundamental role of memory in olfactory perception.

Current emphasis on odorant physiochemical features as the basis for perception largely ignores the synthetic and experience-dependent nature of olfaction. Olfaction is synthetic, as mammals have only limited ability to identify elements within even simple odor mixtures. Furthermore, olfaction is experience-bound, as exposure alone can significantly affect the extent to which stimuli can be discriminated. We propose that early analytical processing of odors is inaccessible at the behavioral level and that all odors are initially encoded as 'objects' in the piriform cortex. Moreover, we suggest that odor perception is wholly dependent on the integrity of this memory system and that its loss severely impairs normal perception.

Animals↗
PubMed2003

Functional brain imaging of olfactory processing in monkeys.

As a step toward bridging the gap between human and animal studies of olfactory brain systems, we report results from an fMRI study of olfaction in squirrel monkeys. High-resolution fMRI images at 3 T with 1.25 x 1.25 x 1.2 mm(3) voxels were obtained covering the whole brain using an 8-cm-diameter birdcage coil and a gradient-echo spiral pulse sequence. Data were acquired from six sedated adult males using a standard block design. All fMRI data were spatially normalized to a common template and analyzed at the individual and group levels with statistical parametric and nonparametric methods. Robust odorant-induced activations were detected in several brain regions previously implicated in conscious human olfactory processing, including the orbitofrontal cortex, cerebellum, and piriform cortex. Consistent with human data, no stimulus intensity effects were observed in any of these regions. Average signal changes in these regions exceeded 0.6%, more than three times the expected signal change based on human fMRI studies of olfaction adjusting for differences in voxel size. These results demonstrate the feasibility of studying olfaction in sedated monkeys with imaging techniques commonly used at 3 T in humans and help promote direct comparisons between humans and nonhuman primates. Our findings, for example, provide novel support for the hypothesis that the cerebellum is involved in sensory acquisition. More broadly, this study suggests that olfactory processing in sedated monkeys and nonsedated humans shares similar neural substrates both within and beyond the primary olfactory system.

Animals↗