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Results for “Olfactory Perception”

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PubMed2004

'Thermal taste' predicts higher responsiveness to chemical taste and flavor.

Individual differences in taste perception have been explained in part by variations in peripheral innervation associated with the genetic ability to taste the bitter substances PTC and PROP. In the present study we report evidence of another source of individual differences that is independent of taste stimulus, taste quality, or gustatory nerve. Individuals who perceived taste from thermal stimulation alone (thermal taste) gave significantly higher taste ratings to chemical stimuli--often by a factor of >2:1--than did individuals who perceived no taste from thermal stimulation. This was true for all taste stimuli tested (sucrose, saccharin, sodium chloride, citric acid, quinine sulfate, MSG and PROP), for all three gustatory areas of the mouth (anterior tongue, posterior tongue and soft palate) and for whole-mouth stimulation. Moreover, the same individuals reported stronger sensations from the olfactory stimulus vanillin, particularly when it was sensed retronasally. The generality of the thermal-taster advantage and its extension to an olfactory stimulus suggests that it arises from individual differences in CNS processes that are involved in perception of both taste and flavor.

Adolescent↗

PubMed2002

Olfactory learning: convergent findings from lesion and brain imaging studies in humans.

The role of temporal lobe structures in olfactory memory was investigated by (i) the examination of odour learning and memory in patients who had undergone resection from a temporal lobe (including primary olfactory regions) for the treatment of intractable epilepsy; and (ii) the examination of brain function during odour memory tasks as assessed via PET imaging of healthy individuals. In order to study different stages of odour memory, recognition of a 'list' of odours was tested after a first exposure, again after four exposures and once more after a 24 h delay interval. Patients with resection from a temporal lobe performed significantly less well than control subjects on all trials, and no significant differences were noted as a function of side of resection, indicating that there is not a strong hemispheric superiority for this task. The PET data yielded different levels of activity in piriform cortex (primary olfactory cortex), in relation to the 'no-odour' baseline scan, depending on the type of processing: no increase in activity noted during odour encoding, a small increase bilaterally during short-term recognition and a larger increase bilaterally during long-term recognition. These findings, together with findings in animal studies, suggest that piriform cortex may have an active role in odour memory processing, not simply in odour perception. Taken together, the findings from the lesion study and functional brain imaging of healthy subjects suggest that olfactory memory requires input from left and right temporal lobe regions for optimal odour recognition, and that, unlike with verbal or non-verbal visual material, there is not a strong functional lateralization for olfactory memory.

Adult↗

PubMed2006

The neurocognitive bases of human multimodal food perception: sensory integration.

This review addresses a fundamental neuroscientific question in food perception: how multimodal features of food are integrated. Much research and conceptualization has emerged related to multisensory integration in vision, audition and somatosensation, while it remains poorly understood and researched within the chemical and mouth feel senses. This review aims to bridge this gap. We discuss the main concepts in the fields of auditory, visual and somatosensory multisensory integration and relate them to oral-sensory (gustatory and somatosensory) and olfactory (orolfactory) interactions. We systematically review the psychophysical literature pertaining to intra- and intermodal interactions related to food perception, while making explicit distinctions between peripheral and central interactions. As the neural bases of crossmodal orolfaction currently are poorly understood, we introduce several plausible neuroscientific models, which provide a framework for further neuroscientific exploration in this area. We are guided by a new meta-analysis of the odor-taste neuroimaging literature, as well as by single-unit, anatomical and psychophysical studies. Finally, we propose strong involvement of recurrent neural networks in multisensory integration and make suggestions for future research.

Animals↗

PubMed2026

Social evolution and diminished olfactory function in larval honey bees.

Social evolution made larval honey bees dependent on adult colony members for feeding; they are confined to cells in waxen honeycombs and visited about 100 times per day by adult "nurse" bees. Based on organismal resource conservation theory, we predicted larvae have diminished olfactory capabilities at both the molecular and behavioral levels. Consistent with theory, larvae expressed very low levels of Orco, an essential gene for olfactory receptor (OR) function. By contrast, they showed higher expression of Ir25a, essential for other forms of sensory perception including gustation. Also consistent with theory, behavioral assays demonstrated that larvae cannot find food via olfaction, suggesting they use taste for feeding. By contrast, it is known that adult honey bees use OR-based olfaction extensively for a variety of behavioral functions, and the honey bee genome contains many OR-encoding genes. Comparative transcriptomic analyses of social and nonsocial insects suggest that this developmentally regulated suppression of olfactory function is related to social evolution, especially systems of offspring care.

Animals↗

PubMed2002

The sense of smell: genomics of vertebrate odorant receptors.

Olfactory receptor (OR) proteins interact with odorant molecules in the nose, initiating a neuronal response that triggers the perception of a smell. The OR family is one of the largest known mammalian gene families, with around 900 genes in human and 1500 in mouse. After discounting pseudogenes, the functional repertoire in mouse is more than three times larger than that of human. OR genes encode G-protein-coupled receptors containing seven transmembrane domains. ORs are arranged in clusters of up to 100 genes dispersed in 40-100 genomic locations. Each neuron in the olfactory epithelium expresses only one allele of one OR gene. The mechanism of gene choice is still unknown, but must involve locus, gene, and allele selection. The gene family has expanded mainly by tandem duplications, many of which have occurred since the divergence of the rodent and primate lineages. Interchromosomal segmental duplications including OR genes have also occurred, but more commonly in the human than the mouse family. As a result, many human OR genes have several possible mouse orthologs, and vice versa. Sequence and copy number polymorphisms in OR genes have been described, which may account for interindividual differences in odorant detection thresholds.

Animals↗

PubMed1994

Olfactory lateralization in the chick.

Chicks using their right nostril (and so with direct olfactory input to the right hemisphere), and presented simultaneously with two objects identical in visual appearance with the rearing object, and differing only in odour, chose that which smelled like the rearing object. Chicks using the left nostril chose equally readily but at random. Earlier work, using similar tests, has shown special interest of the right hemisphere in change in visual properties of familiar stimuli, suggesting that analysis of a wide range of properties of a familiar stimulus may be an important function of the right hemisphere in the chick, with consequent detection of novelty.

Animals↗

PubMed2006

On the trigeminal percept of androstenone and its implications on the rate of specific anosmia.

Specific anosmia is a term that describes an inability to perceive a particular odorant in the context of an otherwise normal olfactory acuity. The most common example, for the odor of androstenone, has been ascribed a prevalence ranging from 2 to 45%. In two experiments we sought to determine whether this wide range could be explained by the difference in steroid concentrations used, and by the degree to which the trigeminal system contributes to perception of androstenone. Experiment 1 demonstrated that high concentrations of androstenone stimulated the trigeminal system, as indicated by electrophysiological recordings. Experiment 2 demonstrated that conscious detection of androstenone is possible based solely on the trigeminal system. Interestingly, detection seems to interact with olfactory acuity in that subjects with a low olfactory sensitivity to androstenone were better able to detect its trigeminal component. The agreement between conscious experience and behavioral discrimination was not well calibrated, in that subjects demonstrated a clear overconfidence in their abilities. Altogether, the current study suggests that androstenone is an odorant that produces a concentration-dependent degree of trigeminal stimulation. This trigeminal component explains the diversity of the reported prevalence of specific anosmia for androstenone and might have implications on future use of specific anosmia as a tool to understand odor processing.

Adult↗

PubMed1985

Olfactory responses in the gustatory area of the parabrachial pons.

Electrophysiological responses to olfactory and gustatory stimuli were recorded in the same neural elements in the parabrachial nuclei (PbN) of rats under Flaxedil. Responses to olfactory stimuli varied in temporal pattern and magnitude from responses to gustatory stimuli. Intravenous infusion of Nembutal while recording from one unit appeared to alter the pattern of responsiveness across stimuli. Most importantly the response to one olfactory stimulus (vanilla) was eliminated by this procedure. Olfactory-gustatory elements were located in the lateral portion of the taste-responsive area of the PbN, just below the brachium conjunctivum. These results suggest that the PbN receives input from both olfactory and gustatory pathways and that these pathways may converge on the same neural elements within the PbN. This convergence may be part of a neurophysiological substrate for the perception of flavor.

Administration, Oral↗

PubMed1998

Temporal processing of odor mixtures reveals that identification of components takes precedence over temporal information in olfactory memory.

Temporal processing of binary mixtures results in odorants being perceived in series separated by many hundreds of milliseconds. Since the odorant perceived first is the main suppressor, knowledge of the order of perception of two odorants can allow prediction of interactions in mixtures. The present study investigated the temporal coding of ternary mixtures composed of carvone, coniferan and triethylamine, and citralva, lillial and triethylamine using a specially constructed air-dilution olfactometer. The results indicated that even though each of the components could be readily identified in ternary mixtures, it was very difficult to indicate which odor was perceived first, with chance scores being recorded. The same outcome occurred even when the 'slowest' odorant was delivered 600 ms after the 'fastest' to the nose. It is proposed that olfactory memory gives precedence to identification of the components of mixtures rather than to their order of perception when more than two odorants are in a mixture.

Humans↗

PubMed2003

Occupational exposure to chemicals and sensory organs: a neglected research field.

The effect of industrial chemicals on the sensory perception of exposed workers has received scant attention from the medical community to date, and the scientific literature is mainly limited to some case-reports or isolated studies. Possible explanations for this include the complexity of sensory perception, and the lack of agreement among researchers on methods for testing large groups of subjects. Nevertheless, some published studies showed that vision, hearing and olfactory function can be affected by various industrial metals and solvents, and some data exist also for touch and taste. This review discusses the main industrial chemicals involved. The pathogenesis of the toxicity of chemicals to sensory perception may be related to an action on receptors, nerve fibers, and/or the brain; probably, different pathogenetic mechanisms are involved. One of the main problems in this research field is that most of the studies to date evaluated the effect of a single industrial chemical on a single sense: as an example, we know that styrene exposure can impair smell and also hearing and vision but we have little idea whether different senses are impaired in the same worker, or whether each impairment is independent. In addition, workers are frequently exposed to different chemicals: co-exposure may have no effect, or result in both an increase or a decrease of the effect, as was observed for hearing loss, but studies on this aspect are largely insufficient. Research shows that both occupational and environmental exposure to industrial chemicals can affect sense organs, and suggests that the decline of perception with age may be, at least partly, related to this exposure. Nevertheless, available evidence is incomplete, and is largely inadequate for an estimation of a "safe" threshold of exposure. Good quality further research in this field is needed. This is certainly complex and demands adequate resources, but is justified by the ultimate result: the possibility to prevent an avoidable part of the decline in sensory function with age.

Animals↗

PubMed2002

Disabling disturbance of olfaction in a dental technician following exposure to methyl methacrylate.

It is often difficult to diagnose dysosmia due to occupational olfactotoxic substances. The authors present a case of disabling disturbance of olfaction in a dental technician. This is very likely to have been caused by exposure to methyl methacrylate. From 1988-1992, the dental technician had very extensive and sustained contact with a self-polymerizing acrylic resin based on methyl methacrylate. Her perception of smell was still normal in 1988, but it deteriorated up to 1992. The olfactory disorders have persisted and impede social life and occupational rehabilitation.

Dental Technicians↗

PubMed1980

The fiber connections of the temporal lobe with emphasis on the rhesus monkey.

The temporal lobe has three functionally distinct areas which have minimal interconnections within the lobe, but extensive connections with other parts of the brain. The superior temporal gyrus contains primary and association auditory areas. Inferotemporal cortex is exclusively a visual association area. The temporal pole is involved in social behavior. In addition, the superior temporal sulcus functions as a sensory integration area. From a review of the literature, a schema is proposed for organizing the reciprocal connections of the three functional areas into a series of loops which follow both cortical and subcortical routes. The afferent and efferent connections of the temporal lobe, phylogenesis, and deficits from lesions are discussed.

Amygdala↗

PubMed1999

Dose-dependent stereoselective activation of the trigeminal sensory system by nicotine in man.

RATIONALE: Nicotine applied to the nasal cavity can evoke 'odorous' sensations in the concentration range near the detection threshold by the activation of the olfactory sensory system and at higher concentrations 'burning' and 'stinging' sensations by the dose-dependent recruitment of C- and Adelta-fibers of the trigeminal sensory system. Neuronal nicotinic acetylcholine receptor (nAchR) subunits are expressed in trigeminal primary afferents and could constitute the receptors involved in nicotine perception. OBJECTIVE: In the present study, we dose-dependently investigated the stereoselective effects of R(+)- and S(-)-nicotine on the trigeminal and olfactory sensory system in man. METHODS: Trigeminal detection thresholds for the 'burning' and 'stinging' sensations and the olfactory detection threshold for the 'odorous' sensation were determined. In order to quantify trigeminal activation, we recorded summated electrical responses from the respiratory nasal mucosa during stimulation with R(+)-and S(-)-nicotine vapor (40, 80, 120, 160 ng/ml; stimulus duration: 250 ms). In addition, subjects rated the intensity of 'odorous', 'burning' and 'stinging' sensations. For chemical stimulation with nicotine enantiomers, a vapor-dilution olfactometer (constant flow rate: 140 ml/s, humidity: 80%, temperature: 37 degrees C, stimulus duration 250 ms) was employed. RESULTS: We found significant stereoselective differences for the trigeminal but not for the olfactory system, i.e. higher summated responses, higher trigeminal intensity estimates, and lower trigeminal detection thresholds for S(-)- compared to R(+)-nicotine. CONCLUSION: Our results clearly demonstrate the different stereoselective activation of the trigeminal sensory system by R(+)-and S(-)-nicotine, indicating the presence of specific stereoselective receptors on trigeminal nociceptive Adelta- and C-fibers.

Adult↗

PubMed2000

Modular representations of odorants in the glomerular layer of the rat olfactory bulb and the effects of stimulus concentration.

To study the mechanism whereby odorants are encoded in the nervous system, we studied the glomerular-layer activity patterns in the rat olfactory bulb evoked by closely related odorants from different chemical families. These odorants had a common straight-chain hydrocarbon structure, but differed systematically in their functional groups. Neural activity was mapped across the entire glomerular layer by using the ¿(14)C2-deoxyglucose method. Group responses were averaged and compared by using data matrices. The glomerular activity patterns that resulted from this analysis were comprised of modules. Unique combinations of modules were activated by each odorant, demonstrating what may be part of the neural code for odorants. Most of the modules were clustered together in the bulb, perhaps providing for enhanced contrast between related chemicals by means of lateral inhibition. We also determined whether changes in odorant concentration would affect spatial patterns of glomerular activity. Two odorants, pentanal and 2-hexanone, evoked different patterns at increased concentrations, with additional glomeruli being recruited at a great distance from glomeruli in which activity was evoked at lower concentrations. Humans report that both of these odorants change in perceived odor with increasing concentration. Three other odorants (pentanoic acid, methyl pentanoate, and pentanol) did not recruit new areas of glomerular activation with increasing concentration, and humans do not report a changed odor across concentrations of these odorants. The results suggest that changes in modular glomerular activity patterns could underlie altered odor perception across odorant concentrations, and they provide additional support for a combinatorial, spatially based code in the olfactory system.

Animals↗

PubMed2006

Gsalpha is involved in sugar perception in Drosophila melanogaster.

In Drosophila melanogaster, gustatory receptor genes (Grs) encode G-protein-coupled receptors (GPCRs) in gustatory receptor neurons (GRNs) and some olfactory receptor neurons. One of the Gr genes, Gr5a, encodes a sugar receptor that is expressed in a subset of GRNs and has been most extensively studied both molecularly and physiologically, but the G-protein alpha subunit (Galpha) that is coupled to this sugar receptor remains unknown. Here, we propose that Gs is the Galpha that is responsible for Gr5a-mediated sugar-taste transduction, based on the following findings: First, immunoreactivities against Gs were detected in a subset of GRNs including all Gr5a-expressing neurons. Second, trehalose-intake is reduced in flies heterozygous for null mutations in DGsalpha, a homolog of mammalian Gs, and trehalose-induced electrical activities in sugar-sensitive GRNs were depressed in those flies. Furthermore, expression of wild-type DGsalpha in sugar-sensitive GRNs in heterozygotic DGsalpha mutant flies rescued those impairments. Third, expression of double-stranded RNA for DGsalpha in sugar-sensitive GRNs depressed both behavioral and electrophysiological responses to trehalose. Together, these findings indicate that DGsalpha is involved in trehalose perception. We suggest that sugar-taste signals are processed through the Gsalpha-mediating signal transduction pathway in sugar-sensitive GRNs in Drosophila.

Animals↗

PubMed2006

Recognition of flowers by pollinators.

The flowers of angiosperm plants present us with a staggering diversity of signal designs, but how did this diversity evolve? Answering this question requires us to understand how pollinators analyze these signals with their visual and olfactory sense organs, and how the sensory systems work together with post-receptor neural wiring to produce a coherent percept of the world around them. Recent research on the dynamics with which bees store, manage and retrieve memories all have fundamental implications for how pollinators choose between flowers, and in turn for floral evolution. New findings regarding how attention, peak-shift phenomena, and speed-accuracy tradeoffs affect pollinator choice between flower species show that analyzing the evolutionary ecology of signal-receiver relationships can substantially benefit from knowledge about the neural mechanisms of visual and olfactory information processing.

Animals↗

PubMed2000

[Signs and symptoms, etiologies and clinical course of parosmia + in a series of 84 patients].

Eighty-four patients (72% females and 28% males) consulted between January 1995 and January 1998 for olfactory disorders with parosmia (erroneous olfactory response to stimuli). Parosmia occurred immediately after or during the course of acute rhinitis (n=70, 83%), head trauma (n=7, 9%), naso-sinus polyposis (n=5, 6%), chronic rhinitis (n=1) or frontal tumor (n=1). Quantitative and qualitative olfactory disorders were analyzed and products producing the parosmia were identified. The only cases where parosmia regressed concerned patients who developed parosmia after acute rhinitis (n=28 cases, 33%). The prognosis of parosmia appeared to be better when it was a secondary phenomenon: i) the percentage of improvements was higher though not significant (41% versus 26.7% compared with primary parosmia), ii) delay to improvement was shorter (8.4 +/- 2.1 months versus 14.5 +/- 4.4 months for primary parosmia, p<10(-4) ), iii) there were no cases of persistent parosmia where quantitative disorders improved (compared with 7 cases of persistent primary parosmia, p<0.05). In addition, the prognosis of associated quantitative disorders was the same for both primary and secondary parosmia. Only the delay to improvement appeared to be shorter in case of secondary parosomia (though the difference was not significant). Products which produced the parosmic perception were identified by nearly all the patients (85%). The most frequently cited products were coffee, perfume, certain fruits (melon, banana, citric fruits), tobacco or chocolate. All these products contain tannic acid, a water-soluble polyphenol with many biological properties (influence feeding habits and metabolism in the rate, antioxidant and antimutagenic properties). Thus acid tannic could induce parosmic perception due to its antioxidant properties susceptible of integrating the P-450 cytochromes of the mucosal cells or olfactory neuroepithelium supporting cells.

Adult↗

PubMed1990

Seasonal shifts in odor acuity by starlings.

A passerine bird, the European Starling Sturnus vulgaris, demonstrated a seasonal ability to respond to odor cues. Cardiac conditioned responses were most evident when birds were in breeding condition. Once birds were in nonbreeding condition, responding to odors all but ceased. For birds in breeding condition, threshold sensitivity to the odor cyclohexanone was comparable to levels reported for nonpasserine birds (0.3% vapor saturation or 3.778 x 10(14) molecules/ml). In contrast, the threshold level during the postreproductive phase of the annual cycle was 10% vapor saturation (1.256 x 10(16) molecules/ml), a level high enough to implicate the trigeminal system as the modality mediating chemosensory perception. The strong cyclic responding pattern suggests links between photoperiodically controlled endocrine production, breeding behavior, and olfactory sensitivity.

Analysis of Variance↗