Showing papers on "Olfaction published in 2004"
TL;DR: Evidence shows that the orbitofrontal cortex is involved in decoding and representing some primary reinforcers such as taste and touch; in learning and reversing associations of visual and other stimuli to these primary rein forcers; and in controlling and correcting reward-related and punishment-related behavior, and thus in emotion.
1,278 citations
TL;DR: The results support the second model of Or83b function, which encodes an atypical odorant receptor that plays an essential general role in olfaction and disrupts behavioral and electrophysiological responses to many odorants.
1,221 citations
TL;DR: In this article, a targeted expression of the green fluorescent protein in chemosensory cells is proposed to characterize receptor-ligand interactions, which is a promising approach to achieve this objective.
Abstract: The chemical senses (smell and taste) have evolved complex repertoires of chemosensory receptors — G-protein coupled receptors with a seven-transmembrane domain structure. In the mouse, ∼1,000 odorant receptors are dedicated to the conventional sense of smell, ∼300 vomeronasal receptors mediate the detection of chemical stimuli (such as pheromones) by the vomeronasal organ, and ∼40 taste receptors are implicated in bitter, sweet and umami taste. Nearly all receptor genes have now been identified as the result of genome sequencing, but few receptor–ligand interactions have been characterized. Targeted expression of the green fluorescent protein in chemosensory cells is a promising approach to achieve this objective.
643 citations
TL;DR: Comparison of odor-evoked activity from afferents and postsynaptic neurons in the same glomerulus revealed that second-order neurons display broader tuning and more complex responses than their primary afferente, implicating lateral interactions within the antennal lobe.
Abstract: Molecular genetics has revealed a precise stereotypy in the projection of primary olfactory sensory neurons onto secondary neurons. A major challenge is to understand how this mapping translates into odor responses in these second-order neurons. We investigated this question in Drosophila using whole-cell recordings in vivo. We observe that monomolecular odors generally elicit responses in large ensembles of antennal lobe neurons. Comparison of odor-evoked activity from afferents and postsynaptic neurons in the same glomerulus revealed that second-order neurons display broader tuning and more complex responses than their primary afferents. This indicates a major transformation of odor representations, implicating lateral interactions within the antennal lobe.
555 citations
TL;DR: The objectives were to investigate the prevalence of olfactory dysfunction in an adult Swedish population and to relate dysfunction to age, gender, diabetes mellitus, nasal polyps, and smoking habits.
Abstract: Objectives/Hypothesis: Patients with olfactory dysfunction appear repeatedly in ear, nose, and throat practices, but the prevalence of such problems in the general adult population is not known. Th ...
493 citations
TL;DR: This work estimates the proportion of OR pseudogenes in 19 primate species by surveying randomly chosen subsets of 100 OR genes from each species and finds that apes, Old World monkeys and one New World monkey, the howler monkey, have a significantly higher proportion ofORS than other New World monkeys or the lemur.
Abstract: Olfactory receptor (OR) genes constitute the molecular basis for the sense of smell and are encoded by the largest gene family in mammalian genomes. Previous studies suggested that the proportion of pseudogenes in the OR gene family is significantly larger in humans than in other apes and significantly larger in apes than in the mouse. To investigate the process of degeneration of the olfactory repertoire in primates, we estimated the proportion of OR pseudogenes in 19 primate species by surveying randomly chosen subsets of 100 OR genes from each species. We find that apes, Old World monkeys and one New World monkey, the howler monkey, have a significantly higher proportion of OR pseudogenes than do other New World monkeys or the lemur (a prosimian). Strikingly, the howler monkey is also the only New World monkey to possess full trichromatic vision, along with Old World monkeys and apes. Our findings suggest that the deterioration of the olfactory repertoire occurred concomitant with the acquisition of full trichromatic color vision in primates.
431 citations
TL;DR: Evaluated the frequency of olfactory dysfunction in a large representative population without sinonasal complaints and investigated the extent to which general pathological conditions, medications, and aging influence olfaction.
Abstract: Objectives/Hypothesis: Goals of the study were to evaluate the frequency of olfactory dysfunction in a large representative population without sinonasal complaints and to investigate the extent to which general pathological conditions, medications, and aging influence olfaction.
Study Design: Prospective.
Methods: Results based on an odor identification test (“Sniffin' Sticks”) were reported from 1240 subjects. The subjects presented themselves to an otorhinolaryngology outpatient clinic with relatively mild and transitory complaints unrelated to the upper airways. A detailed otorhinolaryngological examination in combination with a standardized interview further ascertained that these patients had no rhinological problems or symptoms relating to sinonasal disease.
Results: Apart from the confirmation of the effects of age, gender, and certain otorhinolaryngological diseases on the sense of smell, the study results revealed that certain general diseases (liver diseases, nonotolaryngological cancers) appear to influence olfactory function, whereas other diseases or disorders have little or no impact on olfaction (hypertension, cardiovascular problems).
Conclusion: The data in the study revealed that olfactory dysfunction among subjects under 65 years of age is more frequent than previously reported.
417 citations
TL;DR: Using computational fluid dynamics (CFD) techniques, a method to quickly convert nasal CT scans from an individual patient into an anatomically accurate 3-D numerical nasal model that can be used to predict airflow and odorant transport, which may ultimately determine olfactory sensitivity is developed.
Abstract: Recent studies that have compared CT or MRI images of an individual's nasal anatomy and measures of their olfactory sensitivity have found a correlation between specific anatomical areas and performance on olfactory assessments. Using computational fluid dynamics (CFD) techniques, we have developed a method to quickly (
307 citations
TL;DR: Significant advances in behavioral, physiological and molecular investigations into mosquito host preference are reviewed, with a particular emphasis on studies that have emerged in the post-genomic era that seek to combine these approaches.
300 citations
TL;DR: It is suggested that the increase of dopaminergic neurons in the olfactory bulb is responsible for the hyposmia in Parkinson patients and explains why olfaction does not improve with levodopa therapy.
Abstract: Hyposmia is one of the most prevalent symptoms of Parkinson's disease. It may occur even before the motor symptoms start. To determine whether the olfactory dysfunctions, like the motor symptoms, are associated with a loss of dopamine, the number of dopaminergic cells in the olfactory bulb of Parkinson's disease patients was studied using tyrosine hydroxylase immunohistochemistry. The quantitative analysis reveals that the total number of tyrosine hydroxylase-immunoreactive neurons in the olfactory bulb is twice as high in Parkinson patients compared to age and gender-matched controls. Because dopamine is known to inhibit olfactory transmission in the olfactory glomeruli, we suggest that the increase of dopaminergic neurons in the olfactory bulb is responsible for the hyposmia in Parkinson patients. The increase of dopamine in the olfactory bulb explains why olfaction does not improve with levodopa therapy.
277 citations
TL;DR: Considering patients with idiopathic olfactory dysfunction, noninvasive transcranial sonography seems to be helpful in identifying patients potentially at risk to develop PD.
Abstract: Olfactory loss is among the early signs of Parkinson's disease (PD). We investigated whether "idiopathic" olfactory dysfunction might relate to signs of nigral degeneration. Olfactory tests were combined with transcranial sonography of the substantia nigra and single photon emission computed tomography (SPECT) imaging. Thirty patients diagnosed with idiopathic olfactory loss participated. Eleven of these patients exhibited an increased echogenicity of the SN in the transcranial sonography. In 10 of these 11 patients, SPECT scans with (123)I-FP-CIT were performed. Median uptake ratios in the basal ganglia were pathological in 5 patients, 2 patients exhibited borderline findings, and 3 patients had normal results. Considering patients with idiopathic olfactory dysfunction, noninvasive transcranial sonography seems to be helpful in identifying patients potentially at risk to develop PD. Longitudinal follow-up studies are necessary to estimate the ratio of patients with dopaminergic cell loss in the basal ganglia who will develop PD in the future.
TL;DR: It is found that, before ORN axon arrival, PN dendrites have already created a prototypic map that resembles the adult glomerular map, by virtue of their selective dendritic localization.
Abstract: In both insects and mammals, olfactory receptor neurons (ORNs) expressing specific olfactory receptors converge their axons onto specific glomeruli, creating a spatial map in the brain. We have previously shown that second order projection neurons (PNs) in Drosophila are prespecified by lineage and birth order to send their dendrites to one of ∼50 glomeruli in the antennal lobe. How can a given class of ORN axons match up with a given class of PN dendrites? Here, we examine the cellular and developmental events that lead to this wiring specificity. We find that, before ORN axon arrival, PN dendrites have already created a prototypic map that resembles the adult glomerular map, by virtue of their selective dendritic localization. Positional cues that create this prototypic dendritic map do not appear to be either from the residual larval olfactory system or from glial processes within the antennal lobe. We propose instead that this prototypic map might originate from both patterning information external to the developing antennal lobe and interactions among PN dendrites.
TL;DR: Findings provide convincing neurobiological evidence that the subjective experience of the emotional potency of odor-evoked memory is correlated with specific activation in the amygdala during recall and offers new insights into the affective organization of memory.
TL;DR: This work explores the use of intraspecific chemical cues in burrow recognition and presents evidence for partner-specific odor recognition in a bird.
Abstract: Among birds, the Procellariiform seabirds (petrels, albatrosses, and shearwaters) are prime candidates for using chemical cues for individual recognition These birds have an excellent olfactory sense, and a variety of species nest in burrows that they can recognize by smell However, the nature of the olfactory signature--the scent that makes one burrow smell more like home than another--has not been established for any species Here, we explore the use of intraspecific chemical cues in burrow recognition and present evidence for partner-specific odor recognition in a bird
TL;DR: It appears that only the main olfactory system is implicated when individual odor discrimination of the young is required, and neural structures undergo profound changes when exposed to offspring odors at parturition, contributing both to maternal responsiveness to these odors, to their memorization and to effects of long-term maternal experience.
TL;DR: Results are consistent with a role for AgOr7 in both olfaction and gustation in An.
Abstract: Anopheles gambiae is a highly anthropophilic mosquito responsible for the majority of malaria transmission in Africa. The biting and host preference behavior of this disease vector is largely influenced by its sense of smell, which is presumably facilitated by G protein-coupled receptor signaling [Takken, W. & Knols, B. (1999) Annu. Rev. Entomol. 44, 131-157]. Because of the importance of host preference to the mosquitoes' ability to transmit disease, we have initiated studies intended to elucidate the molecular mechanisms underlying olfaction in An. gambiae. In the course of these studies, we have identified a number of genes potentially involved in signal transduction, including a family of candidate odorant receptors. One of these receptors, encoded by GPRor7 (hereafter referred to as AgOr7), is remarkably similar to an odorant receptor that is expressed broadly in olfactory tissues and has been identified in Drosophila melanogaster and other insects [Krieger, J., Klink, O., Mohl, C., Raming, K. & Breer, H. (2003) J. Comp. Physiol. A 189, 519-526; Vosshall, L. B., Amrein, H., Morozov, P. S., Rzhetsky, A. & Axel, R. (1999) Cell 96, 725-736]. We have observed AgOr7 expression in olfactory and gustatory tissues in adult An. gambiae and during several stages of the mosquitoes' development. Within the female adult peripheral chemosensory system, antiserum against the AgOR7 polypeptide labels most sensilla of the antenna and maxillary palp as well as a subset of proboscis sensilla. Furthermore, AgOR7 antiserum labeling is observed within the larval antenna and maxillary palpus. These results are consistent with a role for AgOr7 in both olfaction and gustation in An. gambiae and raise the possibility that AgOr7 orthologs may also be of general importance to both modalities of chemosensation in other insects.
TL;DR: This review will focus on the chemical nature of mammalian pheromones and the complementary roles of the main olfactory system and vomeronasal system in mediating pheromonal responses and the role of this system in handling information about sex and genetic identity.
TL;DR: This review summarizes the present knowledge about the pathological changes in the olfactory system during aging and in various neurodegenerative diseases.
TL;DR: It is shown that the Anopheles gambiae protein AgOr1, a female-specific member of a family of putative odorant receptors, responds to a component of human sweat, which could function as attractants for trapping mosquitoes or as insect repellents in helping to control Anophele and other insect pests.
Abstract: Female Anopheles mosquitoes, the world's most important vector of Plasmodium falciparum malaria, locate their human hosts primarily through olfactory cues1, but the molecular mechanisms that underlie this recognition are a mystery Here we show that the Anopheles gambiae protein AgOr1, a female-specific member of a family of putative odorant receptors2,3, responds to a component of human sweat Compounds designed to activate or block receptors of this type could function as attractants for trapping mosquitoes or as insect repellents in helping to control Anopheles and other insect pests
TL;DR: The likelihood of pheromonal communication in humans is assessed with a discussion of chemical compounds produced by the axilla that may function as phersomones; the likelihood that the vomeronasal organ (VNO), a putative pheromone receptor organ in many other mammals, is functional in humans; and the possible ways pheramones operate in humans.
Abstract: Among primates in general, pheromones are of variable importance to social communication. Data on humans have generated the greatest controversy regarding the existence of pheromonal communication. In this review, the likelihood of pheromonal communication in humans is assessed with a discussion of chemical compounds produced by the axilla that may function as pheromones; the likelihood that the vomeronasal organ (VNO), a putative pheromone receptor organ in many other mammals, is functional in humans; and the possible ways pheromones operate in humans. In the human axilla, the interactions between the cutaneous microflora and axillary secretions render this region analogous to scent glands found in other primates. Both the chemistry of axillary secretions and their effects on conspecifics in humans appear to be analogous to other mammalian pheromone systems. Whichever chemical compounds serve a pheromonal function in humans, another unknown is the receptor. Although the VNO has been implicated in the reception of pheromones in many vertebrates, it is not the only pathway through which such information has access to the central nervous system; there is ample evidence to support the view that the olfactory epithelium can respond to pheromones. Furthermore, if a chemical activates receptors within the VNO, this does not necessarily mean that the compound is a pheromone. An important caveat for humans is that critical components typically found within the functioning VNO of other, nonprimate, mammals are lacking, suggesting that the human VNO does not function in the way that has been described for other mammals. In a broader perspective, pheromones can be classified as primers, signalers, modulators, and releasers. There is good evidence to support the presence of the former three in humans. Examples include affects on the menstrual cycle (primer effects); olfactory recognition of newborn by its mother (signaler); individuals may exude different odors based on mood (suggestive of modulator effects). However, there is no good evidence for releaser effects in adult humans. It is emphasized that no bioassay-guided study has led to the isolation of true human pheromones, a step that will elucidate specific functions to human chemical signals. © 2004 Wiley-Liss, Inc.
TL;DR: Antennal neurons are both necessary and sufficient for olfaction rhythms, which demonstrates for the first time that a peripheral tissue can function as an autonomous pacemaker in Drosophila.
TL;DR: Another olfactory structure in the nasal septum of animals, the vomeronasal organ, has two additional receptor families that detect pheromones and induce hormonal and behavioral responses through a different projection to the brain.
Abstract: Humans and other mammals perceive a vast number of volatile chemicals as having distinct odors. This ability derives from the existence of a large family of olfactory receptors that number about 350 in man and 1000 in mice. Individual odorants activate distinct combinations of olfactory receptors, generating an immense array of combinatorial receptor codes that define odorant identities. Sensory neurons in the nose express only one receptor type each and connect to the olfactory bulb in a spatially organized manner that yields a stereotyped sensory map. A secondary projection from the bulb to the cortex transforms receptor inputs, generating another, different stereotyped map that may permit the integration of inputs from combinations of receptors. Another olfactory structure in the nasal septum of animals, the vomeronasal organ, has two additional receptor families that detect pheromones and induce hormonal and behavioral responses through a different projection to the brain.
TL;DR: There is a dissociation of olfactory processes, with involvement of the right hemisphere in memory processes and the left hemisphere in emotional processes, and a summary of how these lateralized processes are consistent with the gestalt-nature of the authors' olfaction perception.
Abstract: Over the last ten years, methods of cerebral imaging have revolutionized our knowledge of cognitive processes in humans. An impressive number of papers dealing with cerebral imaging for olfaction have been published to date. Whereas the early works revealed those structures participating in the processing of odours presented passively to subjects, researchers later recorded brain activity when subjects performed specific olfactory tasks based on memory, emotion and identification. From these results, we suggest that there is a dissociation of olfactory processes, with involvement of the right hemisphere in memory processes and the left hemisphere in emotional processes. The review concludes with a summary of how these lateralized processes are consistent with the gestalt-nature of our olfactory perception.
TL;DR: Recent findings regarding plasticity in the mammalian olfactory system that are believed to have general relevance for understanding the neurobiology of memory are described.
Abstract: We are rapidly advancing toward an understanding of the molecular events underlying odor transduction, mechanisms of spatiotemporal central odor processing, and neural correlates of olfactory perception and cognition. A thread running through each of these broad components that define olfaction appears to be their dynamic nature. How odors are processed, at both the behavioral and neural level, is heavily dependent on past experience, current environmental context, and internal state. The neural plasticity that allows this dynamic processing is expressed nearly ubiquitously in the olfactory pathway, from olfactory receptor neurons to the higher-order cortex, and includes mechanisms ranging from changes in membrane excitability to changes in synaptic efficacy to neurogenesis and apoptosis. This review will describe recent findings regarding plasticity in the mammalian olfactory system that are believed to have general relevance for understanding the neurobiology of memory.
TL;DR: Among the "risks" in a risks/benefits discussion with a patient regarding the use of a new medication, alterations in olfaction and taste appear to play an increasingly recognized role.
TL;DR: Data suggest that Kv1.3 plays a far more reaching role in signal transduction, development, and olfactory coding than that of the classically defined role of a potassium channel-to shape excitability by influencing membrane potential.
TL;DR: Rule learning regulates the composition of synaptic NMDARs in the piriform cortex, resulting in receptors with a higher complement of the NR2a subunit protein relative to NR2b.
TL;DR: Studies on the effects of stimuli from multiple sensory modalities on the brain of humans and some other higher primates are reviewed, striking that humans and other catarrhines interface the visual system to other sensory systems in the orbitofrontal cortex.
Abstract: In primates, stimuli to sensory systems influence motivational and emotional behavior via neural relays to the orbitofrontal cortex. This article reviews studies on the effects of stimuli from multiple sensory modalities on the brain of humans and some other higher primates. The primate orbitofrontal cortex contains the secondary taste cortex, in which the reward value of taste is represented. It also contains the secondary and tertiary olfactory cortical areas, in which information about the identity and also about the reward value of odors is represented. A somatosensory input is revealed by neurons that respond to the viscosity of food in the mouth, to the texture (mouth feel) of fat in the mouth, and to the temperature of liquids placed into the mouth. The orbitofrontal cortex also receives information about the sight of objects from the temporal lobe cortical visual areas. Information about each of these modalities is represented separately by different neurons, but in addition, other neurons show convergence between different types of sensory input. This convergence occurs by associative learning between the visual or olfactory input and the taste. In that emotions can be defined as states elicited by reinforcers, the neurons that respond to primary reinforcers (such as taste and touch), as well as learn associations to visual and olfactory stimuli that become secondary reinforcers, provide a basis for understanding the functions of the orbitofrontal cortex in emotion. In complementary neuroimaging studies in humans, it is being found that areas of the orbitofrontal cortex are activated by pleasant touch, by painful touch, by taste, by smell, and by more abstract reinforcers such as winning or losing money. Damage to the orbitofrontal cortex in humans can impair the learning and reversal of stimulus-reinforcement associations and thus the correction of behavioral responses when these are no longer appropriate because previous reinforcement contingencies change. It is striking that humans and other catarrhines, being visual specialists like other anthropoids, interface the visual system to other sensory systems (e.g., taste and smell) in the orbitofrontal cortex.
TL;DR: In sheep, preventing the vomeronasal organ (VNO) from functioning does not affect the female responses to male odor suggesting that, unlike in rodents, the accessory olfactory system does not play the major role in the perception of this pheromonal cue.
TL;DR: Research findings have confirmed a role for olfactory testing in the differential diagnosis of movement disorders, and suggest that this approach is currently underused in clinical practice.
Abstract: Purpose of review Marked olfactory dysfunction (hyposmia) is a frequent and early abnormality in Parkinson's disease. We review recent advances related to its cause and its clinical relevance with respect to the differential diagnosis of Parkinsonian syndromes.Recent findings Marked olfactory dysfunction occurs in Parkinson's disease and dementia with Lewy bodies but is not found in progressive supranuclear palsy and corticobasal degeneration. In multiple system atrophy, the deficit is mild and indistinguishable from cerebellar syndromes of other aetiologies, including the spinocerebllar ataxias. This is in keeping with evidence of cerebellar involvement in olfactory processing, which may also help to explain recent findings of mild olfactory dysfunction in essential tremor. Smell testing remains, however, a clinically relevant tool in the differential diagnosis of indeterminate tremors. Intact olfaction has also been reported recently in Parkin disease (PARK 2) and vascular Parkinsonism. The relevance of sniffing ability to olfaction and a possible role of increased tyrosine hydroxylase and dopamine in parts of the olfactory bulb are issues of current interest with respect to pathophysiology. The early or 'pre-clinical' detection of Parkinson's disease is increasingly recognized as an area in which olfactory testing may be of value.Summary Research findings have confirmed a role for olfactory testing in the differential diagnosis of movement disorders, and suggest that this approach is currently underused in clinical practice. Validated test batteries are now available that may prove to be of practical use in the differential diagnosis of Parkinsonian syndromes and indeterminate tremors.