Showing papers on "Olfaction published in 2002"
TL;DR: It is demonstrated that prevalence of olfactory impairment among older adults is high and increases with age, and self-report significantly underestimated prevalence rates obtained by olfaction testing.
Abstract: Context Older adults represent the fastest-growing segment of the US population, and prevalences of vision and hearing impairment have been extensively evaluated. However, despite the importance of sense of smell for nutrition and safety, the prevalence of olfactory impairment in older US adults has not been studied. Objective To determine the prevalence of olfactory impairment in older adults. Design, setting, and participants A total of 2491 Beaver Dam, Wis, residents aged 53 to 97 years participating in the 5-year follow-up examination (1998-2000) for the Epidemiology of Hearing Loss Study, a population-based, cross-sectional study. Main outcome measures Olfactory impairment, assessed by the San Diego Odor Identification Test and self-report. Results The mean (SD) prevalence of impaired olfaction was 24.5% (1.7%). The prevalence increased with age; 62.5% (95% confidence interval [CI], 57.4%-67.7%) of 80- to 97-year-olds had olfactory impairment. Olfactory impairment was more prevalent among men (adjusted prevalence ratio, 1.92; 95% CI, 1.65-2.19). Current smoking, stroke, epilepsy, and nasal congestion or upper respiratory tract infection were also associated with increased prevalence of olfactory impairment. Self-reported olfactory impairment was low (9.5%) and this measure became less accurate with age. In the oldest group, aged 80 to 97 years, sensitivity of self-report was 12% for women and 18% for men. Conclusions This study demonstrates that prevalence of olfactory impairment among older adults is high and increases with age. Self-report significantly underestimated prevalence rates obtained by olfaction testing. Physicians and caregivers should be particularly alert to the potential for olfactory impairment in the elderly population.
929 citations
TL;DR: Human ORs cover a similar 'receptor space' as the mouse ORs, suggesting that the human olfactory system has retained the ability to recognize a broad spectrum of chemicals even though humans have lost nearly two-thirds of the OR genes as compared to mice.
Abstract: Olfactory receptor (OR) genes are the largest gene superfamily in vertebrates. We have identified the mouse OR genes from the nearly complete Celera mouse genome by a comprehensive data mining strategy. We found 1,296 mouse OR genes (including ∼20% pseudogenes), which can be classified into 228 families. OR genes are distributed in 27 clusters on all mouse chromosomes except 12 and Y. One OR gene cluster matches a known locus mediating a specific anosmia, indicating the anosmia may be due directly to the loss of receptors. A large number of apparently functional 'fish-like' Class I OR genes in the mouse genome may have important roles in mammalian olfaction. Human ORs cover a similar 'receptor space' as the mouse ORs, suggesting that the human olfactory system has retained the ability to recognize a broad spectrum of chemicals even though humans have lost nearly two-thirds of the OR genes as compared to mice.
899 citations
TL;DR: The results provide direct support for the functional relevance of correlation codes and shed some light on the role of oscillatory synchronization in sensory networks.
Abstract: In the insect olfactory system, oscillatory synchronization is functionally relevant and reflects the coherent activation of dynamic neural assemblies. We examined the role of such oscillatory synchronization in information transfer between networks in this system. The antennal lobe is the obligatory relay for olfactory afferent signals and generates oscillatory output. The mushroom body is responsible for formation and retrieval of olfactory and other memories. The format of odor representations differs significantly across these structures. Whereas representations are dense, dynamic, and seemingly redundant in the antennal lobe, they are sparse and carried by more selective neurons in the mushroom body. This transformation relies on a combination of oscillatory dynamics and intrinsic and circuit properties that act together to selectively filter and synthesize the output from the antennal lobe. These results provide direct support for the functional relevance of correlation codes and shed some light on the role of oscillatory synchronization in sensory networks.
792 citations
TL;DR: Using anosmic mice, it is found that sensory input was critical for the survival of GCs from day 15 to 45 after labeling and suggests possible functions of OB cell replacement.
Abstract: Young neurons born in the subventricular zone (SVZ) of adult mice migrate to the olfactory bulb (OB) where they differentiate into granule cells (GCs) and periglomerular interneurons. Using retroviral labeling of precursors in the SVZ, we describe five stages and the timing for the maturation of newly formed GCs: (1) tangentially migrating neuroblasts (days 2-7); (2) radially migrating young neurons (days 5-7); (3) GCs with a simple unbranched dendrite that does not extend beyond the mitral cell layer (days 9-13); (4) GCs with a nonspiny branched dendrite in the external plexiform layer (days 11-22); and (5) mature GCs (days 15-30). Using [3H]thymidine, we show that the maximum number of labeled GCs is observed around day 15 after injection. Interestingly, between days 15 and 45 after birth, soon after the cells developed spines, the number of [3H]thymidine-labeled GCs declined by 50%. Using anosmic mice, we found that sensory input was critical for the survival of GCs from day 15 to 45 after labeling. However, the number and morphology of 15-d-old cells in the granule cell layer was similar in anosmic and wild-type mice. We infer that the lack of activity did not have an effect on the generation, migration, and early differentiation of granule cells. Soon after young GCs matured, and presumably became synaptically connected, their survival depended on the level of activity that they received. This selection mechanism might allow the construction of specific OB circuits based on olfactory experience and suggests possible functions of OB cell replacement.
705 citations
TL;DR: It is shown that adult mice housed in odor-enriched cages display improved olfactory memory without a change in spatial learning performance, suggesting that ongoing bulbar neurogenesis could be associated with improved o aroma memory.
Abstract: In the mammalian forebrain, most neurons originate from proliferating cells in the ventricular zone lining the lateral ventricles, including a discrete area of the subventricular zone (SVZ). In this region, neurogenesis continues into adulthood. Most of the cells generated in the SVZ are neuronal precursors with progeny that migrate rostrally along a pathway known as the rostral migratory stream before they reach the main olfactory bulb (MOB) where they differentiate into local interneurons. The olfactory system thus provides an attractive model to investigate neuronal production and survival, processes involving interplay between genetic and epigenetic influences. The present study was conducted to investigate whether exposure to an odor-enriched environment affects neurogenesis and learning in adult mice. Animals housed in either a standard or an odor-enriched environment for 40 d were injected intraperitoneally with bromodeoxyuridine (BrdU) to detect proliferation among progenitor cells and to follow their survival in the MOB. The number of BrdU-labeled neurons was not altered 4 hr after a single BrdU injection. In contrast, the number of surviving progenitors 3 weeks after BrdU injection was markedly increased in animals housed in an enriched environment. This effect was specific because enriched odor exposure did not influence hippocampal neurogenesis. Finally, we showed that adult mice housed in odor-enriched cages display improved olfactory memory without a change in spatial learning performance. By maintaining a constitutive turnover of granule cells subjected to modulation by environmental cues, ongoing bulbar neurogenesis could be associated with improved olfactory memory.
692 citations
TL;DR: The findings suggest that the role of human primary (piriform) and secondary olfactory cortices transcends their function as mere intermediaries of chemosensory information processing and imply that emotionally salient odors can engender cross-modal associative learning.
Abstract: We combined event-related functional magnetic resonance imaging (fMRI) with olfactory classical conditioning to differentiate the neural responses evoked during appetitive and aversive olfactory learning. Three neutral faces [the conditioned stimuli (CS+)] were repetitively paired with pleasant, neutral, or unpleasant odors [the unconditioned stimuli (UCS)] in a partial reinforcement schedule. A fourth face was never paired to odor [the nonconditioned stimulus (CS-)]. Learning-related neural activity, comparing unpaired (face only) CS+ stimuli with CS-, showed valence-independent activations in rostral and caudal orbitofrontal cortex (OFC). Medial OFC responded to the appetitive (app) CS+, whereas lateral OFC responded to the aversive (av) CS+. Within nucleus accumbens, neural responses showed divergent activation profiles that increased with time in response to the appCS+ but decreased in response to the avCS+. In posterior amygdala, responses were elicited by the appCS+, which habituated over time. In temporal piriform cortex, neural responses were evoked by the avCS+, which progressively increased with time. These results highlight regional and temporal dissociations during olfactory learning and imply that emotionally salient odors can engender cross-modal associative learning. Moreover, the findings suggest that the role of human primary (piriform) and secondary olfactory cortices transcends their function as mere intermediaries of chemosensory information processing.
441 citations
TL;DR: The data provide evidence that ORs determine both odorant specificity and axonal convergence and thus direct functionally similar afferents to form particular glomeruli and confirm and extend the notion that OR expression provides a molecular basis for the formation and arrangement of glomerular functional units.
Abstract: Odorant receptors (ORs) mediate the interaction of odorous compounds with olfactory sensory neurons (OSNs) and influence the guidance of OSN axons to synaptic targets in the olfactory bulb (OB). OSNs expressing the same OR send convergent axonal projections to defined glomeruli in the OB and are thought to share the same odorant response properties. This expectation of functional similarity has not been tested experimentally, because it has not been possible to determine reproducibly the response properties of OSNs that express defined ORs. Here, we applied calcium imaging to characterize the odorant response properties of single neurons from gene-targeted mice in which the green fluorescent protein is coexpressed with a particular OR. We show that the odorants acetophenone and benzaldehyde are agonists for the M71 OR and that M71-expressing neurons are functionally similar in their response properties across concentration. Replacing the M71 coding sequence with that of the rat I7 OR changes the stimulus response profiles of this genetically defined OSN population and concomitantly results in the formation of novel glomeruli in the OB. We further show that the mouse I7 OR imparts a particular response profile to OSNs regardless of the epithelial zone of expression. Our data provide evidence that ORs determine both odorant specificity and axonal convergence and thus direct functionally similar afferents to form particular glomeruli. They confirm and extend the notion that OR expression provides a molecular basis for the formation and arrangement of glomerular functional units.
395 citations
TL;DR: The results indicate functional heterogeneity in areas critical to human olfaction and show that brain regions mediating emotional processing are differentially activated by odor valence, providing evidence for a close anatomical coupling between olfactory and emotional processes.
Abstract: Studies of patients with focal brain injury indicate that smell perception involves caudal orbitofrontal and medial temporal cortices, but a more precise functional organization has not been characterized. In addition, although it is believed that odors are potent triggers of emotion, support for an anatomical association is scant. We sought to define the neural substrates of human olfactory information processing and determine how these are modulated by affective properties of odors. We used event-related functional magnetic resonance imaging (fMRI) in an olfactory version of a classical conditioning paradigm, whereby neutral faces were paired with pleasant, neutral, or unpleasant odors, under 50% reinforcement. By comparing paired (odor/face) and unpaired (face only) conditions, odor-evoked neural activations could be isolated specifically. In primary olfactory (piriform) cortex, spatially and temporally dissociable responses were identified along a rostrocaudal axis. A nonhabituating response in posterior piriform cortex was tuned to all odors, whereas activity in anterior piriform cortex reflected sensitivity to odor affect. Bilateral amygdala activation was elicited by all odors, regardless of valence. In posterior orbitofrontal cortex, neural responses evoked by pleasant and unpleasant odors were segregated within medial and lateral segments, respectively. The results indicate functional heterogeneity in areas critical to human olfaction. They also show that brain regions mediating emotional processing are differentially activated by odor valence, providing evidence for a close anatomical coupling between olfactory and emotional processes.
336 citations
TL;DR: The use of the genetically encoded calcium-sensitive fluorescence protein cameleon 2.1 in the Drosophila brain is reported, and calcium imaging with a genetically encoded fluorescence probe is shown to be feasible in a brain in vivo.
227 citations
TL;DR: Analysis of isolated cDNA‐clones of a heliothine moth led to the discovery of a divergent gene family encoding putative seven‐transmembrane domain proteins, which strongly suggest that the newly discovered gene family indeed encodes olfactory receptors of moth.
Abstract: The antennae of moths have been an invaluable model for studying the principles of odour perception. In spite of the enormous progress in understanding olfaction on the molecular level, for the moth one of the key elements in olfactory signalling, the odourant receptors, are still elusive. We have assessed a genome database of a heliothine moth (Heliothis virescens, Noctuidae) and employed exon-specific probes to screen an antennal cDNA library of this species. Analysis of isolated cDNA-clones led to the discovery of a divergent gene family encoding putative seven-transmembrane domain proteins. The notion that they may encode candidate olfactory receptors of the moth, was supported by a tissue-specific expression; several of the subtypes were exclusively expressed in antennae. By means of double-labelling in situ hybridization studies it was demonstrated that the receptors are indeed expressed in antennal sensory neurons; moreover, each receptor subtype appears to be expressed in a distinct population of sensory cells. The results strongly suggest that the newly discovered gene family indeed encodes olfactory receptors of moth.
223 citations
TL;DR: Sequence and copy number polymorphisms in OR genes have been described, which may account for interindividual differences in odorant detection thresholds.
Abstract: 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.
TL;DR: A genetic screen for negative regulators of olfaction uncovered mutations in the cG MP-dependent protein kinase EGL-4 that disrupt olfactory adaptation in C. elegans, suggesting that adaptation is a cell intrinsic process initiated by cGMP.
TL;DR: Both quantitative measurements of perceptual similarity and comparability with 2-deoxyglucose imaging data from the olfactory bulb are dependent on the specific behavioral tasks used, and behavioral indices of perceptual similarities are affected by task parameters such as learning and reward associations.
Abstract: Carbon chain length in several classes of straight-chain aliphatic odorants has been proposed as a model axis of similarity for olfactory research, on the basis of successes of studies in insect and vertebrate species. To assess the influence of task on measured perceptual similarities among odorants and to demonstrate that the systematic similarities observed within homologous odorant series are not task specific, the authors compare 3 different behavioral paradigms for rats (olfactory habituation, generalization, and discrimination). Although overall patterns of odorant similarity are consistent across all 3 of these paradigms, both quantitative measurements of perceptual similarity and comparability with 2-deoxyglucose imaging data from the olfactory bulb are dependent on the specific behavioral tasks used. Thus, behavioral indices of perceptual similarity are affected by task parameters such as learning and reward associations.
TL;DR: The interaction between the olfactory and trigeminal systems is not straightforward and may be difficult to predict, but it has a powerful influence on the perception of odors.
Abstract: Objectives: The review outlines characteristics of the intranasal trigeminal chemosensory system. In addition, it provides selective comparisons of the trigeminal and olfactory systems, the two of which interact at multiple levels. Results and Conclusions: This interaction between the trigeminal and olfactory systems is an important determinant of sensations of odor. Further, it appears to change as a result of aging and disease. Thus, the interaction between the olfactory and trigeminal systems is not straightforward and may be difficult to predict, but it has a powerful influence on the perception of odors.
TL;DR: Treatment for phantosmia includes assurance with no active therapy, topical medications, systemic medications, anesthesia to parts of the nose and, rarely, referral for surgical excision of olfactory neurons.
Abstract: Clinically, olfaction can fail in any of three ways: (i) decreased sensitivity (hyposmia, anosmia) and two types of distortion (dysosmia); (ii) distorted quality of an odorant stimulation (troposmia); (iii) perceived odor when no odorant is present (phantosmia, hallucination). The distortions are usually much more upsetting to a person's quality of life than a simple loss. An ipsilatersal loss of olfactory sensitivity is often identified in the nostril with any type of olfactory distortion. The pathophysiology of a stimulated distortion (troposmia) is likely a decreased number of functioning olfactory primary neurons so that an incomplete characterization of the odorant is made. In phantosmia, two possible causations include an abnormal signal or inhibition from the primary olfactory neurons or peripheral olfactory or trigeminal signals that "trigger" a central process. The clinician's goal is to carefully define the problem (e.g. taste versus smell, real versus perceived, one versus two nostrils), to perform the appropriate examination and testing and to provide therapy if possible. Treatment includes assurance with no active therapy (because many of these will naturally resolve), topical medications, systemic medications, anesthesia to parts of the nose and, rarely, referral for surgical excision of olfactory neurons. Endoscopic transnasal operations have the advantage of treating phantosmia and sometimes allowing a return of olfactory ability after the operation.
TL;DR: The olfactory system sits at the interface of the environment and the nervous system and is responsible for correctly coding sensory information from thousands of odorous stimuli, and the downstream consequences of this cascade that regulates multiple second messengers and perhaps even gene transcription in response to the initial interaction of ligand with G protein-coupled receptor are understood.
Abstract: ▪ Abstract The olfactory system sits at the interface of the environment and the nervous system and is responsible for correctly coding sensory information from thousands of odorous stimuli. Many theories existed regarding the signal transduction mechanism that mediates this difficult task. The discovery that odorant transduction utilizes a unique variation (a novel family of G protein–coupled receptors) based upon a very common theme (the G protein–coupled adenylyl cyclase cascade) to accomplish its vital task emphasized the power and versatility of this motif. We now must understand the downstream consequences of this cascade that regulates multiple second messengers and perhaps even gene transcription in response to the initial interaction of ligand with G protein–coupled receptor.
01 Jan 2002
TL;DR: Olfactory cognition at the start of life: the perinatal shaping of selective odor responsiveness Benoist Schaal, Robert Soussignan and Luc Marlier 27.
Abstract: Foreword Acknowledgements A tribute to Edmond Roudnitska 1. Olfaction and cognition: a philosophical and psychoanalytical view Annick Le Guerer 2. Cognitive aspects of olfaction in perfumer practice Andre Holley 3. The specific characteristics of the sense of smell Egon Peter Koster 4. Names and categories for odors: the 'veridical label' Daniele Dubois 5. Nose-wise: olfactory metaphors in mind David Howes 6. Linguistic expressions of odors in French Sophie David 7. Classification of odors and structure-odor relationships Maurice Chastrette 8. The acquisition and activation of odor hedonics in everyday situations: conditioning and priming studies Dick Hermans and Frank Baeyens 9. Is there a hedonic dimension of odors? Catherine Rouby and Moustafa Bensafi 10. The influence of odors on mood and affective cognition Rachel S. Herz 11. Assessing putative human pheromones Suma Jacob, Bethanne Zelano, Davinder J. S. Hayreh and Martha K. McClintock 12. The neural correlates of emotion perception: from faces to taste Mary L. Phillips and Maike Heining 13. Testing odor memory: incidental vs. intentional learning implicit vs. explicit memory Sylvie Issanchou, Dominique Valentin, Claire Sulmont, Joachim Degel and Egon Peter Koster 14. Odor memory: a memory systems approach Maria Larsson 15. Repetition priming in odor memory Mats J. Olsson, Maria Faxbrink and Fredrik U. Jonsson 16. Odor memory in Alzheimer's disease Steven Nordin and Claire Murphy 17. Development of odor naming and odor memory from childhood to young adulthood Johannes Lehrner and Peter Walla 18. Odor coding at the periphery of the olfactory system Gilles Sicard 19. On human brain activity within the first second after odor presentation Bettina M. Pause 20. Processing of olfactory affective information: contribution of functional imaging studies Robert J. Zatorre 21. Experience-induced changes reveal functional dissociation within olfactory pathways Nadine Ravel, Anne-Marie Mouly, Pascal Chabaud and Remi Gervais 22. Increased taste sensitivity by familiarization to 'novel' stimuli Annick Faurion, Barbara Cerf, Anne-Maria Pillias and Nathalie Boireau 23. The cortical representation of taste and smell Edmund T. Rolls 24. New psychophysical insights in evaluating genetic variation in taste Katharine Fast, Valerie B. Duffy and Linda M. Bartoshuk 25. The individuality of odor perception Robyn Hudson and Hans DisTel 26. Olfactory cognition at the start of life: the perinatal shaping of selective odor responsiveness Benoist Schaal, Robert Soussignan and Luc Marlier 27. Age-related changes of chemosensory functions Thomas Hummel, S. Heilman and Claire Murphy Index.
TL;DR: Analysis of testing for odor threshold, olfactory discrimination and identification in idiopathic Parkinson's disease (IPD) and nonidiopathy Parkinson's syndrome (PS) added to previous findings and suggested that Olfactory probes improve the diagnostic armamentarium in IPD.
Journal Article•
TL;DR: The olfactory sulcus is deeper on the right than on the left, particularly in patients with IA, and it is speculated that olfaction may be processed predominantly in the right hemisphere.
Abstract: BACKGROUND AND PURPOSE: Anosmias with chromosomal disorders has been well investigated. However, isolated anosmia (IA) has received less attention, although it occurs more frequently. We compared frontobasal structures in patients with IA since birth or early childhood with those in control subjects. METHODS: Imaging findings obtained in 16 patients with IA were compared with those obtained in eight control subjects. Imaging was performed with a standard quadrature head coil at 1.5 T. T1-weighted spin-echo (coronal plane perpendicular to frontal skull base; section thickness, 3 mm; pixels, 0.43 × 0.39 mm) and sagittal T1-weighted magnetization-prepared rapid gradient-echo (voxels, 1.0 × 1.0 × 1.0 mm) sequences were performed. We assessed the length and depth of the olfactory sulcus, olfactory bulb volume, and olfactory sulcus depth in the plane of the posterior tangent through the eyeballs (PPTE). RESULTS: Five patients with IA had bilateral hypoplastic olfactory bulbs. Three patients with IA had hypoplastic olfactory bulbs on the right and aplastic olfactory bulbs on the left. Eight patients with IA had bilaterally aplastic olfactory bulbs. The depth of the olfactory sulcus at the level of the PPTE was smaller in patients with IA than in control subjects. The depth of the olfactory sulcus was greater on the right than on the left, and there was no overlap. Among patients with IA, the depth of the olfactory sulcus differed significantly between those with and those without visible olfactory tracts. CONCLUSION: The depth of the olfactory sulcus at the level of the PPTE reflects the presence of olfactory tracts. The presence or absence of the olfactory tract may therefore have some association with cortical growth of the olfactory sulcus region. The olfactory sulcus is deeper on the right than on the left, particularly in patients with IA. We speculate that olfaction may be processed predominantly in the right hemisphere.
TL;DR: This paper examines four examples of features of olfactory systems in members of different phyla, and analyzes data from nematodes, arthropods, molluscs, and vertebrates to investigate the phylogenetic distribution of these features, and to try to explain the presence of them in disparate animals.
Abstract: As we learn more about the neurobiology of olfaction, it is becoming increasingly clear that olfactory systems of animals in disparate phyla possess many striking features in common. Why? Do these features provide clues about the ways the nervous system processes olfactory information? This might be the case if these commonalities are convergent adaptations that serve similar functions, but similar features can be present in disparate animals for other reasons. For example, similar features may be present because of inheritance from a common ancestor (homology), may represent responses to similar constraints, or may be superficial or reflect strategies used by researchers studying the system. In this paper, I examine four examples of features of olfactory systems in members of different phyla: the presence of odorant binding proteins in the fluid overlying olfactory receptor neurons; the use of G protein-coupled receptors as odorant receptors; the use of a two-step pathway in the transduction of odorant signals; and the presence of glomerular neuropils in the first central target of the axons of olfactory receptor cells. I analyze data from nematodes, arthropods, molluscs, and vertebrates to investigate the phylogenetic distribution of these features, and to try to explain the presence of these features in disparate animals. Phylogenetic analyses indicate that these features are not homologous across phyla. Although these features are often interpreted as convergent adaptations, I find that alternative explanations are difficult to dismiss. In many cases, it seems that olfactory system features that are similar across phyla may reflect both responses to similar constraints and adaptations for similar tasks.
TL;DR: Olfactory tests differentiate IPD from non-IPD, and tests of olfactory function may also be of interest in investigations related to treatment of PS.
Abstract: Olfactory loss is a prominent symptom in idiopathic Parkinson's disease (IPD). Experiment 1 re-investigated the diagnostic value of psychophysical testing in the differentiation between idiopathic Parkinson disease (IPD) from non-IPD; 50 consecutive PS patients participated. In Experiment 2 five de-novo patients received 3 olfactory tests spread over a period of appoximately one year. Nineteen IPD patients were anosmic, and 18 were hyposmic. All but one patient with MSA and PSP had mild/moderate hyposmia. Normosmia was found in CBD/misdiagnosed PS/psychogenic movement disorder. In Experiment 2, one of the de-novo patients was normosmic, 3 hyposmic, and 1 anosmic. Follow up investigations indicated decreased olfactory function in 3 patients while it improved in one. The normosmic patient retained olfactory abilities. This patient failed to respond to pharmacological treatment. In summary, olfactory tests differentiate IPD from non-IPD. Furthermore, tests of olfactory function may also be of interest in investigations related to treatment of PS.
TL;DR: The largely reduced numbers of afferents and the similar architecture of the LAL and the adult antennal lobe render the larval chemosensory system of Drosophila a valuable model system, both for studying smell and taste and for examining the development of its adult organization.
Abstract: We provide a detailed analysis of the larval head chemosensory system of Drosophila melanogaster, based on confocal microscopy of cell-specific reporter gene expression in P[GAL4] enhancer trap lines. In particular, we describe the neuronal composition of three external and three pharyngeal chemosensory organs, the nerve tracts chosen by their afferents, and their central target regions. With a total of 21 olfactory and 80 gustatory neurons, the sensory level is numerically much simpler than that of the adult. Moreover, its design is different than in the adult, showing an association between smell and taste sensilla. In contrast, the first-order relay of the olfactory afferents, the larval antennal lobe (LAL), exhibits adult-like features both in terms of structure and cell number. It shows a division into approximately 30 subunits, reminiscent of glomeruli in the adult antennal lobe. Taken together, the design of the larval chemosensory system is a "hybrid," with larval-specific features in the periphery and central characteristics in common with the adult. The largely reduced numbers of afferents and the similar architecture of the LAL and the adult antennal lobe, render the larval chemosensory system of Drosophila a valuable model system, both for studying smell and taste and for examining the development of its adult organization.
TL;DR: It is suggested that the function of lateral inhibition in the olfactory bulb may be to compensate for generalized, spatially distributed activation that otherwise may obscure the specific, discrete patterns of glomerular activation seen across the ofactory bulb.
TL;DR: Interestingly, controlling for odor naming ability resulted in that the observed sex difference in episodic odor memory for familiar odors disappeared, which suggests that women's superiority in episodi odor memory is largely mediated by their higher proficiency in odor identification.
Abstract: We investigated sex difference across a number of olfactory tasks. Thirty-six men and 35 women ranging in age from 19 to 36 years were assessed in 6 different tasks: absolute sensitivity for n-butanol, intensity discrimination, quality discrimination, episodic recognition memory for familiar and unfamiliar odors, and odor identification. No sex differences were observed in the tasks tapping primarily sensory acuity (i.e., odor sensitivity, intensity discrimination, and quality discrimination) or in episodic memory for unfamiliar odors. By contrast, women outperformed men in the tasks involving verbal processing (i.e., memory for familiar odors and odor identification). Interestingly, controlling for odor naming ability resulted in that the observed sex difference in episodic odor memory for familiar odors disappeared. This outcome suggests that women's superiority in episodic odor memory is largely mediated by their higher proficiency in odor identification.
TL;DR: 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 olf factory memory.
Abstract: 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.
Received November 6, 2000. Revised June 8, 2001. Second revision August 10, 2001. Accepted August 29, 2001.
TL;DR: These results are the first to show enhancement of sensory responses in the olfactory cortex by LC activation, and suggest that spontaneous activation of LC neurons such as occurs during learning could serve to enhanceOlfactory perception and promote learning.
Abstract: Piriform cortex (PCx) is the primary cortical projection region for olfactory information and has bidirectional monosynaptic connections with olfactory bulb and association cortices. PCx neurons display a complex receptive field, responding to odours rather than their molecular components, suggesting that these neurons are involved in higher order olfactory processing. Neuromodulators, especially noradrenaline (NA), have important influences on sensory processing in other cortical regions and might be responsible for the plasticity observed in PCx during learning. The present study is the first attempt to examine in vivo the actions of NA on sensory responses in the PCx. Stimulation of the noradrenergic nucleus locus coeruleus (LC) was used to induce release of NA in the forebrain in urethane-anaesthetized rats. Extracellular recording of single units was made simultaneously in anterior and posterior PCx. The responses to an odour stimulus were measured over 25 trials. Twenty-five subsequent odour presentations were preceded by stimulation of the ipsilateral LC through a bipolar electrode, previously placed in the LC under electrophysiological control. This priming stimulation modified the activity of 77 of the 135 recorded neurons. For most cells, LC stimulation enhanced cortical responses to odour in terms of both spike count and temporal organization, with some differential effects in anterior and posterior regions. These results are the first to show enhancement of sensory responses in the olfactory cortex by LC activation. Spontaneous activation of LC neurons such as occurs during learning could serve to enhance olfactory perception and promote learning.
TL;DR: The sense of smell seems to be organized similarly to other sensory modalities, and the specific psychophysical characteristics of olfaction should be attributed to an early involvement of the limbic system rather than to a conceptually different mode of processing.
TL;DR: Results reveal that two nasal segments are important for inter-individual differences of odor thresholds in healthy subjects: the segment in the upper meatus below the cribriform plate and the anterior segment of the inferior meatus.
Abstract: The aim of this exploratory study was to identify the volume intranasal segments as they relate to parameters of olfactory function. Fifty healthy male volunteers (age range 22-59 years, mean age 28.5 years) were included. Olfactory function was measured by lateralized phenyl ethyl alcohol odor thresholds and odor discrimination, and by bilateral odor identification. Magnetic resonance imaging of the nasal cavity was performed immediately following olfactometry. To correlate the results of olfactometry with intranasal volume, each nasal cavity was divided into 11 segments. Significant correlations were found between the odor thresholds and volumes of the anterior part of the lower and upper meatus of the right nasal cavity. These results reveal that two nasal segments are important for inter-individual differences of odor thresholds in healthy subjects: (i) the segment in the upper meatus below the cribriform plate and (ii) the anterior segment of the inferior meatus. The latter finding is of special interest for nasal surgery, which allows modification of this volume through resection of the inferior turbinate and/or septoplasty.
TL;DR: In this paper, the attractive properties of volatile and nonvolatile components of the male-soiled bedding have been analyzed in female mice that had no previous experience with adult male-derived chemical signals (chemically naive females) using two-choice preference tests.
TL;DR: Investigation of the potential therapeutic effects of α‐lipoic acid in olfactory loss following infections of the upper respiratory tract found possible mechanisms of actions include the release of nerve growth factor and antioxidative effects, both of which may be helpful in the regeneration of Olfactory receptor neurons.
Abstract: Objectives/hypothesis The study aimed to investigate the potential therapeutic effects of alpha-lipoic acid in olfactory loss following infections of the upper respiratory tract. Possible mechanisms of actions include the release of nerve growth factor and antioxidative effects, both of which may be helpful in the regeneration of olfactory receptor neurons. Study design Unblinded, prospective clinical trial. Methods A total of 23 patients participated (13 women, 10 men; mean age 57 y, age range 22-79 y; mean duration of olfactory loss, 14 mo; range, 4 to 33 mo); 19 of them were hyposmic and 4 had functional anosmia. Alpha-lipoic acid was used orally at a dose of 600 mg/day; it was prescribed for an average period of 4.5 months. Olfactory function was assessed using olfactory tests for phenyl ethyl alcohol odor threshold, odor discrimination, and odor identification. Results Seven patients (30%) showed no change in olfactory function. Two patients (9%) exhibited a moderate decrease in olfactory function; in contrast, six patients (26%) showed moderate and eight patients (35%) remarkable increase in olfactory function. Two of the 4 patients with functional anosmia reached hyposmia; 5 of 19 hyposmic patients became normosmic. Overall, this resulted in a significant improvement in olfactory function following treatment (P =.002). At the end of treatment parosmias were less frequent (22%) than at the beginning of therapy (48%). Interestingly, recovery of olfactory function appeared to be more pronounced in younger patients than in patients above the age of 60 years (P =.018). Conclusions The results indicate that alpha-lipoic acid may be helpful in patients with olfactory loss after upper respiratory tract infection. However, to judge the true potential of this treatment, the outcome of double-blind, placebo-controlled studies in large groups of patients must be awaited, especially when considering the relatively high rate of spontaneous recovery in olfactory loss after upper respiratory tract infection.