Olfactory Ability Research Articles

Blue tits (Cyanistes caeruleus) respond to an experimental change in the aromatic plant odour composition of their nest

Although the use of olfaction by birds is now widely recognised, the olfactory abilities of passerine birds remain poorly explored, for historical reasons. Several studies however suggest that passerines can perceive volatile compounds in several biologically relevant contexts. In Corsica, recent findings suggest that cavity-nesting blue tits may use volatile compounds in the context of nest building and maintenance. Although they build their nests mainly from moss, female blue tits also frequently incorporate fragments of several species of aromatic plants in the nest cup. In field experiments, breeding female blue tits altered their nest maintenance behaviour in response to experimental addition of aromatic plants in their nest. In aviary experiments, captive male blue tits could be trained to detect lavender odour from a distance. Here I report results from a field study aimed to test whether adult blue tits altered their chick-feeding behaviour after an experimental change in nest odour composition. I experimentally added fragments of aromatic plant species that differed from those brought in the nests before the start of the experiment in a set of experimental nests and added moss, the basic nest material, in a set of control nests. Both male and female blue tits hesitated significantly longer entering the nest cavity after addition of new aromatic plant fragments, as compared to moss addition. This response was especially observed during the first visit following the experimental change in nest plant composition. Nest composition treatment had no effect on the time spent in the nest. This study demonstrates that free-ranging blue tits detect changes in nest odour from outside the nest cavity.

Nasal Fossa of Mouse and Dwarf Lemurs (Primates, Cheirogaleidae)

Dimensions of the external midface in mammals are sometimes related to olfactory abilities (e.g., "olfactory snouts" of strepsirrhine primates). This association hinges on the largely unexplored relationship between the protruding midface and internal topography of the nasal fossae. Herein, serially sectioned heads of embryonic to adult cheirogaleid primates (mouse and dwarf lemurs) and a comparative sample were studied. To assess the anteroposterior distribution of olfactory epithelium (OE) within the nasal fossa, the surface area of OE and non-OE was measured in two mouse lemurs (one adult, one infant). Prenatally, ethmoturbinal projections appear in an anteroposterior sequence. Fetal mouse lemurs, tenrecs, voles, and flying lemurs have four ethmoturbinals that project toward the nasal septum. Major distinctions among these mammals include the number of turbinals in recesses and the extent of the olfactory recess. Surface area measurements in the adult mouse lemur reveal that 31% of the entire nasal fossa is lined with OE. The majority is sequestered in a posterior recess (70% OE). Anterior to this space, only 28% of the nasal fossa is lined with OE. Ethmoturbinal I is lined with relatively less OE (35%) compared with more posterior ethmoturbinals (46-57%). Age comparisons support the idea that OE increases less than non-OE between ages. Regionally, results suggest that most growth in surface area occurs in turbinals. But in all ethmoturbinals, surface area of non-OE differs between ages more than that of OE. This study shows that the anterior part of the nasal fossa is mostly nonolfactory in Microcebus murinus.

Brain architecture in the terrestrial hermit crab Coenobita clypeatus(Anomura, Coenobitidae), a crustacean with a good aerial sense of smell

BackgroundDuring the evolutionary radiation of Crustacea, several lineages in this taxon convergently succeeded in meeting the physiological challenges connected to establishing a fully terrestrial life style. These physiological adaptations include the need for sensory organs of terrestrial species to function in air rather than in water. Previous behavioral and neuroethological studies have provided solid evidence that the land hermit crabs (Coenobitidae, Anomura) are a group of crustaceans that have evolved a good sense of aerial olfaction during the conquest of land. We wanted to study the central olfactory processing areas in the brains of these organisms and to that end analyzed the brain of Coenobita clypeatus (Herbst, 1791; Anomura, Coenobitidae), a fully terrestrial tropical hermit crab, by immunohistochemistry against synaptic proteins, serotonin, FMRFamide-related peptides, and glutamine synthetase.ResultsThe primary olfactory centers in this species dominate the brain and are composed of many elongate olfactory glomeruli. The secondary olfactory centers that receive an input from olfactory projection neurons are almost equally large as the olfactory lobes and are organized into parallel neuropil lamellae. The architecture of the optic neuropils and those areas associated with antenna two suggest that C. clypeatus has visual and mechanosensory skills that are comparable to those of marine Crustacea.ConclusionIn parallel to previous behavioral findings of a good sense of aerial olfaction in C. clypeatus, our results indicate that in fact their central olfactory pathway is most prominent, indicating that olfaction is a major sensory modality that these brains process. Interestingly, the secondary olfactory neuropils of insects, the mushroom bodies, also display a layered structure (vertical and medial lobes), superficially similar to the lamellae in the secondary olfactory centers of C. clypeatus. More detailed analyses with additional markers will be necessary to explore the question if these similarities have evolved convergently with the establishment of superb aerial olfactory abilities or if this design goes back to a shared principle in the common ancestor of Crustacea and Hexapoda.

Auditory and olfactory abilities of larvae of the Indo‐Pacific coral trout Plectropomus leopardus (Lacepède) at settlement

Auditory and olfactory abilities of settlement‐stage larvae of the coral trout Plectropomus leopardus (Pisces: Serranidae) were tested electrophysiologically to determine if these senses are sufficiently developed to aid larvae in detection of settlement habitats on coral reefs. Plectropomus leopardus larvae detected sounds from 100 to 2000 Hz with hearing most sensitive at the frequencies of 100, 200 and 600 Hz. The olfactory response of P. leopardus was similar for the two amino acids tested and for the water conditioned by conspecifics. Auditory and olfactory abilities of P. leopardus are well developed at settlement‐stage, and apparently sufficient to detect auditory and olfactory cues from reefs.

Sensory ecology on the high seas: the odor world of the procellariiform seabirds

Procellariiform seabirds wander the world's oceans aided by olfactory abilities rivaling those of any animal on earth. Over the past 15 years, I have been privileged to study the sensory ecology of procellariiforms, focusing on how olfaction contributes to behaviors, ranging from foraging and navigation to individual odor recognition, in a broader sensory context. We have developed a number of field techniques for measuring both olfactory- and visually based behaviors in chicks and adults of various species. Our choice of test odors has been informed by long-term dietary studies and geochemical data on the production and distribution of identifiable, scented compounds found in productive waters. This multidisciplinary approach has shown us that odors provide different information over the ocean depending on the spatial scale. At large spatial scales (thousands of square kilometers), an olfactory landscape superimposed upon the ocean surface reflects oceanographic or bathymetric features where phytoplankton accumulate and an area-restricted search for prey is likely to be successful. At small spatial scales (tens to hundreds of square kilometers), birds use odors and visual cues to pinpoint and capture prey directly. We have further identified species-specific, sensory-based foraging strategies, which we have begun to explore in evolutionary and developmental contexts. With respect to chemical communication among individuals, we have shown that some species can distinguish familiar individuals by scent cues alone. We are now set to explore the mechanistic basis for these discriminatory abilities in the context of kin recognition, and whether or not the major histocompatibility complex is involved.

Canine Olfactory Receptor Gene Polymorphism and Its Relation to Odor Detection Performance by Sniffer Dogs

The outstanding sensitivity of the canine olfactory system has been acknowledged by using sniffer dogs in military and civilian service for detection of a variety of odors. It is hypothesized that the canine olfactory ability is determined by polymorphisms in olfactory receptor (OR) genes. We investigated 5 OR genes for polymorphic sites which might affect the olfactory ability of service dogs in different fields of specific substance detection. All investigated OR DNA sequences proved to have allelic variants, the majority of which lead to protein sequence alteration. Homozygous individuals at 2 gene loci significantly differed in their detection skills from other genotypes. This suggests a role of specific alleles in odor detection and a linkage between single-nucleotide polymorphism and odor recognition efficiency.

The Susceptibility of Olfactory Measures to Malingering

Few studies have assessed the effect of malingering on behavioral measures of olfactory functioning. Understanding the limitations of these measures may aid in the accurate interpretation of atypical test results produced by research participants and patients assessed in clinical settings. This study investigated the susceptibility of two measures of olfaction to naive and sophisticated attempts to malinger. Sixty particpants were randomly assigned to three conditions that varied in the amount of coaching they received on how to successfully malinger on two measures of olfactory dysfunction. Both the University of Pennslyvania Smell Identification Test (UPSIT) and the Sniff Magnitude Test (SMT: a measure of odor-induced sniff suppression) appear susceptible to malingering. The UPSIT was more successful at detecting naive malingerers than the SMT, but even modest coaching enabled most participants to successfully fake an olfactory impairment. The SMT was more resistant to malingering than the UPSIT in that the majority of participants attempting to fake an olfactory deficit performed in the normal range. The combination of the two tests proved to be the most effective approach to the accurate assessment of olfactory ability.

Effects of Pre- and Postnatal Exposure to Chromium Picolinate or Picolinic Acid on Neurological Development in CD-1 Mice

Chromium picolinate, Cr(pic)3, a popular dietary supplement marketed as an aid in fat loss and lean muscle gain, has also been suggested as a therapy for women with gestational diabetes. The current study investigated the effects of maternal exposure to Cr(pic)3 and picolinic acid during gestation and lactation on neurological development of the offspring. Mated female CD-1 mice were fed diets from implantation through weaning that were either untreated or that contained Cr(pic)3 (200 mg kg(-1) day(-1)) or picolinic acid (174 mg kg(-1) day(-1)). A comprehensive battery of postnatal tests was administered, including a modified Fox battery, straight-channel swim, open-field activity, and odor-discrimination tests. Pups exposed to picolinic acid tended to weigh less than either control or Cr(pic)3-exposed pups, although the differences were not significant. Offspring of picolinic acid-treated dams also appeared to display impaired learning ability, diminished olfactory orientation ability, and decreased forelimb grip strength, although the differences among the treatment groups were not significant. The results indicate that there were no significant effects on the offspring with regard to neurological development from supplementation of the dams with either Cr(pic)3 or picolinic acid.

Olfactory identification ability in schizophrenia spectrum disorders

Schizophrenia may be conceptualised using a dimensional approach to examine trait-like expression such as schizotypy within non-clinical populations to better understand pathophysiology. A candidate psychosis-risk marker, the auditory mismatch negativity (MMN) is thought to index the functionality of glutamatergic NMDA receptor mediated neurotransmission. Although the MMN is robustly reduced in patients with schizophrenia, the association between MMN and schizotypy in the general population is under-investigated. Thirty-five healthy participants completed the Schizotypal Personality Questionnaire (SPQ) and a multi-feature MMN paradigm (standards 82%, 50 ms, 1000 Hz, 80 dB) with duration (100 ms), frequency (1200 Hz) and intensity (90 dB) deviants (6% each). Spearman's correlations were used to explore the association between schizotypal personality traits and MMN amplitude. Few associations were identified between schizotypal traits and MMN. Higher Suspiciousness subscale scores tended to be correlated with larger frequency MMN amplitude. A median-split comparison of the sample on Suspiciousness scores showed larger MMN (irrespective of deviant condition) in the High compared to the Low Suspiciousness group. The trend-level association between MMN and Suspiciousness is in contrast to the robustly attenuated MMN amplitude observed in schizophrenia. Reductions in MMN may reflect a schizophrenia-disease state, whereas non-clinical schizotypy may not be subserved by similar neuropathology.

Dissociation of age and ability on a visual analogue of the University of Pennsylvania Smell Identification Test in children with autism

Early olfactory identification deficits have been associated with neurodevelopmental arrest of limbic-prefrontal networks. These same networks are implicated in development of autistic-spectrum disorders. We aimed to investigate olfactory identification ability in children with high functioning autism (HFA). Fifteen children with HFA (aged 5–9 years) and 15 age-, gender- and IQ-matched controls (CTL) were compared on their performance on a visual analogue of the University of Pennsylvania Smell Identification Test (UPSIT). The hypothesis that children with HFA would exhibit impaired olfactory identification ability was not supported. However, contrary to the relationship found in the CTLs, smell identification ability was negatively associated with age in HFA. The results suggest some disruption of normal developmental association between olfactory ability and age in HFA. The visual analogue of the UPSIT warrants further investigation to determine its validity and reliability in normal and other clinical populations.

No association between psychometrically-determined schizotypy and olfactory identification ability in first-degree relatives of patients with schizophrenia and non-psychiatric controls

Objective This study examined potential associations between schizotypy—including positive, negative, and disorganized domains—and olfactory identification ability. Based on a prior report (Park, S., Schoppe, S., 1997. Olfactory identification deficit in relation to schizotypy. Schizophr. Res. 26, 191–197), it was hypothesized that positive and negative schizotypy would be associated with poorer olfactory identification ability, at least among male participants. Method As part of a larger study, the Schizotypal Personality Questionnaire (SPQ) and University of Pennsylvania Smell Identification Test (UPSIT) were administered to 98 participants, including 44 healthy first-degree relatives of individuals with schizophrenia and related disorders and 54 non-psychiatric controls. Potential associations between SPQ subscales and UPSIT score were examined while considering the effects of sociodemographic variables on these measures. Results SPQ and UPSIT scores were not significantly different in first-degree relatives and controls. There was no evidence of an association between SPQ domains and UPSIT score, even when controlling for possible confounding variables, including age and educational attainment. Conclusions The nascent literature on potential associations between schizotypy and olfactory identification ability has yielded mixed findings to date. The current study does not support a correlation between these two markers, and this lack of association—in addition to equal olfactory identification performance in relatives and controls—casts doubt on the utility of the UPSIT as a measure of an endophenotypic trait. Future research would benefit from larger, more diverse samples; the addition of objective, interviewer-based measures of schizotypy; and attention to potentially confounding sociodemographic variables.

Development of the nasal olfactory organs in the larvae, settlement-stages and some adults of 14 species of Caribbean reef fishes (Labridae, Scaridae, Pomacentridae)

Larval fishes likely use a variety of settlement cues to locate and navigate toward the habitats they will inhabit as juveniles. Information about the morphology and state of development of the sensory organs of larval stages of fishes provides insight into their capabilities at the time of settlement. The peripheral olfactory organ of wild-caught late-stage larvae and early juveniles and some adults of 14 species of the Caribbean reef fishes wrasses (Labridae), parrot fishes (Scaridae) and damselfish (Pomacentridae) were examined using scanning electron microscopy and compared in terms of settlement specificity. Ages in days after hatching and days post-settlement were determined from the otoliths. Morphology of the nares and the olfactory epithelium are described for these species by stage. The separation of the anterior and posterior nares occurred before settlement in the labrids but in some specimens of scarids this separation was not complete by the time of settlement. Densities of ciliated and microvillous receptor cells and non-sensory ciliated epithelial cells were calculated. Densities of ciliated receptor cells ranged from 0.389 μm−2 in a specimen of Thallasoma bifasciatum to 0.0057 μm−2 in Bodianus rufus and of microvillous receptor cells from 0.038 μm−2 in a Clepticus parrae juvenile to 0.266 μm−2 in a juvenile Doratonotus megalepis. Densities of non-sensory cilia, also associated with high olfactory ability, were also high. The olfactory organ in wrasses is well developed prior to settlement and is comparable to that of adult fishes. The possible role of olfaction in larval schooling, reef cue detection and orientation toward habitat at settlement is discussed.

Lateralisation of intranasal trigeminal chemosensory event-related potentials

To determine whether or not chemosensory event-related brain potentials (CSERP) elicited by nociceptive unilateral intranasal (CO2) trigeminal stimulation are lateralized and, if they are, whether this hemispheric lateralization is related to the side of the stimulated nostril. Nine healthy right-handed subjects participated to the study. CSERPs were recorded after left or right monorhinal CO2 stimulation. Latency and baseline-to-peak amplitude of each CSERP component were compared across stimulation conditions (left and right nostril), scalp locations (lower-frontal, frontal, mid-temporal, central, posterior-temporal, parietal) and hemispheres (left or right), using a three-factor analysis of variance (ANOVA) for repeated measures. Intranasal trigeminal CO2 stimulation elicited a large N400-P550 complex. This complex was preceded by an earlier N300 component. Whatever the stimulated nostril, N300, N400 and P550 amplitudes were significantly higher on the right as compared to the left hemisphere, at lower-frontal recording sites. The side of chemosensory stimulation (left or right nostril) did not significantly affect CSERP components. This study showed that in healthy right-handed volunteers with normal olfactory ability, intranasal chemosensory trigeminal stimulation may elicit a series of event-related brain potentials, which all display a significant right-hemisphere predominance, irrespective of the stimulated nostril. The observed lateralization was maximal at lower-frontal recording sites.

One‐year longitudinal evaluation of sensorimotor functions in APP751SL transgenic mice

Intracerebral amyloid-beta (Abeta) peptide deposition is considered to play a key role in Alzheimer's disease and is designated as a principal therapeutic target. The relationship between brain Abeta levels and clinical deficits remains, however, unclear, both in human patients and in animal models of the disease. The purpose of the present study was to investigate, in a transgenic mouse model of brain amyloidosis, the consequences of Abeta deposition on basic neurological functions using a longitudinal approach. Animals were phenotyped at different ages corresponding to graded neuropathological stages (from no extracellular Abeta deposition to high amyloid loads). Sensory functions were evaluated by assessing visual and olfactory abilities and did not show any effects of the amyloid precursor protein (APP) transgene. Motor functions were assessed using multiple experimental paradigms. Results showed that motor strength was considerably reduced in APP transgenic mice compared with control animals. No deficit was noted in a motor coordination test although APP transgenic mice displayed decreased locomotion on a stationary beam. Hypolocomotion was also observed in the standard open-field test. Measures of anxiety obtained in the elevated plus-maze show some evidence of hyperanxiety in 15-month-old transgenic mice. Some of the neurological impairments showed by APP mice had an early onset and worsened with progressive aging, in parallel to gradual accumulation of Abeta in brain parenchyma. Relationships between neuropathologically assessed amyloid loads and behavioral deficits were further explored, and it was observed that motor strength deficits were correlated with cortical amyloid burden.

Olfactory Alterations in Allergic Rhinitis to Pollens and Mites

In the last 80 years, the presence of allergies has increased among Europeans from 0.28% to 14.2%. Allergic rhinitis is the main presentation, rising from 18% to 40% of cases. The aim of this study is to demonstrate that allergic rhinitis due to pollen and mites has an effect on the olfactory system. We describe the impairment of olfactory function in two groups of individuals with allergic rhinitis due to mites or pollen (n = 76; 42 with allergy to pollen [48.9%], and 34 with allergy to mites [39%]), compared with a group of healthy volunteers (n = 120). Olfactory ability was measured by the BAST-24 (Barcelona Smell Test) olfactometer comprising 20 odours tested by the forced choice method to compare the levels of odour detection (knowing if there is odour in the environment), and efficacy (identifying what was smelt). The results show firstly that people with allergic rhinitis have a clear, definitive, and significant impairment (P >.05) in olfactory levels; secondly, there is a tendency towards greater olfactory loss in the case of people with pollen-related allergic rhinitis than in those allergic to mites; and thirdly, the different odours are affected differently in the 2 groups. We propose consideration of the study of olfactory status in the assessment of patients with allergic rhinitis.

Odours Grab His Hand but Not Hers

Gender is important for the determination of olfactory abilities. Previous reports on gender differences in human odour perception claimed that the sensitivity and discrimination ability of females for odours is superior to that of males. Evolutionary theories, however, open up the possibility of an interesting dissociation between females and males in terms of odour processing: there is an advantage for women for the perceptual aspects of olfactory stimuli and an advantage for men when translating perceptual olfactory information into action. In line with this hypothesis our observations suggest that encoding odours has the ability to guide the movement of males but not that of females.

The superosmic phenomenon

Olfaction studies in the institution of Department of Otorhinolaryngology at Leicester Royal Infirmary have detected a previously unreported, variable phenomenon--'superosmia'--in which subjects' olfaction threshold concentrations are up to 100,000 smaller than the average value. The aim of this report is to define and quantify this phenomenon. Two hundred and thirty subjects, who had been screened for active nasal pathology (age range 20-60 years), underwent individual olfactory threshold tests for phenylethyl alcohol or eucalyptol, using a computer-driven olfactometer in a controlled laboratory setting. Some tests were single tests and others were repeated on a small cohort. Two per cent of subjects demonstrated the superosmic phenomenon on single testing, and 10 per cent demonstrated this phenomenon on variable occasions during repeated testing. The superosmic phenomenon was defined by: (1) confident olfactory perception of a threshold at least equal to if not greater than three threshold levels below the subject's average threshold; (2) repeated perception of the odour at this level for at least 10 responses (1:1024 probability of chance finding); and (3) (where time permitted) a sudden, rapid loss of superosmia. Superosmia is a distinct phenomenon, the stimulus or mechanism of which is currently the subject of further research. The enhancement of olfactory ability may be possible through activation of an accessory pathway or modulation of the existing olfactory apparatus.

Sex differences in olfactory function in young patients with psychotic disorders

Female superiority on many measures of olfactory function is well established, but debate remains as to whether this pattern extends to patients with psychotic disorders. The purpose of this large retrospective study was to re-examine whether male vs. female differences in olfactory identification exist in patients with psychotic disorders, and if so, whether any such differences were related to features of the psychotic disorder or could be explained by a generalized male–female difference. We examined 353 relatively young patients, recently diagnosed with a psychotic illness, (258 males and 95 females) and compared these with 89 healthy control subjects (45 males and 44 females). All individuals had been assessed birhinally using the University of Pennsylvania Smell Identification Test (UPSIT). Overall, females were superior to males, and patients underperformed healthy controls. No interaction was noted between these two variables, and there was no significant effect found as a result of age of the subjects. The data suggested that sex differences in olfactory identification ability exist in young patients with psychotic disorders. They do not appear to be related to exposure to antipsychotic medication or smoking habit. Therefore, it is likely that they represent basic male vs. female differences and not diagnosis-specific sex differences in olfactory performance—at least in those who are in the early stages of illness.

Olfactory discrimination ability and brain expression of c-fos, Gir and Glut1 mRNA are altered in n − 3 fatty acid-depleted rats

The long-chain polyunsaturated n − 3 fatty acids ( n − 3 PUFA), particularly docosahexaenoic acid (DHA), are abundantly present in the central nervous system and play an important role in cognitive functions such as learning and memory. We, therefore, investigated the effects of n − 3 PUFA-depletion in rats (F2 generation) on the learning of an olfactory discrimination task, progressively acquired within a four-arm maze, and on the mRNA expression of some candidate genes, i.e., c-fos, Gir and glucose transporter (Glut1), which could reflect the level of cerebral activity. We observed that DHA contents were dramatically decreased in the olfactory bulb, the piriform cortex and the neocortex of n − 3-depleted rats. Furthermore, the n − 3 deficiency resulted in a mild olfactory learning impairment as these rats required more days to master the olfactory task compared to control rats. Real-time RT-PCR experiments revealed that the training induced the expression of c-fos mRNA in all the three regions of the brain whereas Gir and Glut1 mRNA were induced only in olfactory bulb and neocortex. However, such an increase was less marked in the n − 3-deficient rats. Taken together, these results allow us to assume that the behavioural impairment in n − 3-deficient rats is linked to the depletion of n − 3 fatty acids in brain regions processing olfactory cues. Data are discussed in view of the possible role of some of these genes in learning-induced neuronal olfactory plasticity.

Evaluation of Long-Term Occupational Exposure to Styrene Vapor on Olfactory Function

The primary sensory neurons of the olfactory system are chronically exposed to the ambient environment and may therefore be susceptible to damage from occupational exposure to many volatile chemicals. To investigate whether occupational exposure to styrene was associated with olfactory impairment, we examined olfactory function in 2 groups: workers in a German reinforced-plastics boat-manufacturing facility having a minimum of 2 years of styrene exposure (15-25 ppm as calculated from urinary metabolite concentrations, with historical exposures up to 85 ppm) and a group of age-matched workers from the same facility with lower styrene exposures. The results were also compared with normative data previously collected from healthy, unexposed individuals. Multiple measures of olfactory function were evaluated using a standardized battery of clinical assessments from the Monell-Jefferson Chemosensory Clinical Research Center that included tests of threshold sensitivity for phenylethyl alcohol (PEA) and odor identification ability. Thresholds for styrene were also obtained as a measure of occupational olfactory adaptation. Styrene exposure history was calculated through the use of past biological monitoring results for urinary metabolites of styrene (mandelic acid [MA], phenylglyoxylic acid [PGA]); current exposure was determined for each individual using passive air sampling for styrene and biological monitoring for styrene urinary metabolites. Current mean effective styrene exposure during the day of olfactory testing for the group of workers who worked directly with styrene resins was 18 ppm styrene (standard deviation [SD] = 14), 371 g/g creatinine MA + PGA (SD = 289) and that of the group of workers with lower exposures was 4.8 ppm (SD = 5.2), 93 g/g creatinine MA+PGA (SD = 100). Historic annual average exposures for all workers were greater by a factor of up to 6x. No differences unequivocally attributable to exposure status were observed between the Exposed and Comparison groups or between performance of either group and normative population values on thresholds for PEA or odor identification. Although odor identification performance was lower among workers with higher ongoing exposures, performance on this test is not a pure measure of olfactory ability and is influenced by familiarity with the stimuli and their sources. Consistent with exposure-induced sensory adaptation, however, elevated styrene thresholds were significantly associated with higher occupational exposures to styrene. In summary, the present study found no evidence among a cross-section of reinforced-plastics workers that current or historical exposure to styrene was associated with a general impairment of olfactory function. When taken together with prior studies of styrene-exposed workers, these results suggest that styrene is not a significant olfactory toxicant in humans at current exposure levels.