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PubMed1984

Olfactory cuing of autobiographical memory.

In Experiment 1, subjects were presented with either the odors or the names of 15 common objects. In Experiment 2, subjects were presented with either the odors, photographs, or names of 16 common objects. All subjects were asked to describe an autobiographical memory evoked by each cue, to date each memory, and to rate each memory on vividness, pleasantness, and the number of times that the memory had been thought of and talked about prior to the experiment. Compared with memories evoked by photographs or names, memories evoked by odors were reported to be thought of and talked about less often prior to the experiment and were more likely to be reported as never having been thought of or talked about prior to the experiment. No other effects were consistently found, though there was a suggestion that odors might evoke more pleasant and emotional memories than other types of cues. The relation of these results to the folklore concerning olfactory cuing is discussed.

Cues↗
PubMed1995

Twin analysis of odor identification and perception.

Findings from the first twin analysis using the University of Pennsylvania Smell Identification Test (UPSIT) and a phenyl ethyl alcohol (PEA) threshold detection test are presented. A genetic influence on odor identification was suggested for males, but not for females, consistent with previous twin research on physical measures. In addition, females scored significantly higher on the UPSIT than males. A curvilinear age trend for odor identification was detected for males, but not for females. In contrast, neither genetic, age, nor gender effects were suggested for PEA sensitivity. Performance on the olfactory tests was unrelated to scores on standard measures of intelligence.

Adolescent↗
PubMed1999

Behavioral responses to aliphatic aldehydes can be predicted from known electrophysiological responses of mitral cells in the olfactory bulb.

For a better understanding of the encoding of odor quality in the olfactory system, it is critical to determine how electrophysiological responses to odorants are reflected in the behavioral responses to these odorants. In this article, we use a simple behavioral paradigm to show that the behavioral responses to similar odorants can be predicted from the electrophysiological responses of neurons in the olfactory bulb. Carbon chain length in aliphatic aldehydes has been used as a model for graded similarity among odorants. Recent electrophysiological experiments have shown that mitral cells in the rabbit olfactory bulb respond with similar response patterns to aliphatic aldehydes of similar chain length. On average, mitral cells responded with increased spiking activity to stimulation with two to three different aldehydes of neighboring chain length. We here show that the perception of these odorants can be predicted from the electrophysiological responses: rats that are conditioned to a given aldehyde generalize to aldehydes with one to two carbon differences in chain length from the conditioned aldehyde. When asked to discriminate between aldehydes of different chain lengths, rats learned to discriminate between any two odorants, but the rate of acquisition depended on the degree of similarity between the two odorants.

Aldehydes↗
PubMed1998

Perception of scent over-marks by golden hamsters (Mesocricetus auratus): novel mechanisms for determining which individual's mark is on top.

Hamsters preferentially remember or value the top scent of a scent over-mark. What cues do they use to do this? Using habituation-discrimination techniques, we exposed male golden hamsters (Mesocricetus auratus) on 3 to 4 trials to genital over-marks from 2 females and then tested subjects for their familiarity with these 2 scents compared with that of a novel female's secretion. Preferential memory for 1 of the 2 individuals' scents did not occur if the 2 marks did not overlap or did not overlap but differed in age, but it did occur if a region of overlap existed or 1 mark apparently occluded another (but did not overlap it). Thus, hamsters use regions of overlap and the spatial configuration of scents to evaluate over-marks. These phenomena constitute evidence for previously unsuspected perceptual abilities, including olfactory scene analysis, which is analogous to visual and auditory scene analysis.

Analysis of Variance↗
PubMed1978

Invariance of odor strength with sniff vigor: an olfactory analogue to size constancy.

Previous evidence has shown that detection threshold in humans and olfactory neural discharge rate in animal preparations both depend on flow rate of odorous vapor. But no data have been reported that show the effects of flow rate in humans on perceived odor strength at suprathreshold intensities. Subjects learned to inspire at two flow rates, one twice as great as the other, by adjusting (on a cathode ray tube) the transduced trace of a sniff-produced pressure change to match either of two target contours. They then made magnitude estimations of odor strength, while producing either weak or strong sniffs, for odorants presented over a wide range of concentrations via a specially designed sniff-bottle system. The odorant, diluted in diethyl phthalate, was n-butanol in two experiments and n-amyl acetate in two others. Subject-controlled flow rate had no effect on odor strength for either odorant. There was an apparent contradiction between these data and those on neural discharge rate that may, however, be resolved by adopting an odor constancy model: When sniff intensity varies during the olfactory exploration of an odor source, information about the rate at which odorant molecules are established at the receptor site is combined with information about sniff vigor so that the resulting percept is of invariant odor strength.

Acetates↗
PubMed1993

Response to short photoperiod and spontaneous sexual recrudescence in the lesser mouse lemur: role of olfactory bulb removal.

The body weight and sexual activity of the male lesser mouse lemur, a prosimian primate, undergo cyclic changes that are photoperiod-dependent. Exposure to long daylength (LD; 14 h light/day) led to sustained sexual activity, fully developed testes and high plasma testosterone concentrations (228 +/- 25 nmol/l, n = 10). After 14 weeks under LD, a marked decrease in testosterone levels occurred. Gonadal regression was completed within 20 weeks under LD without concomitant changes in body weight. Exposure to short daylength (SD; 8 h light/day) reinforced the sexual quiescence and was associated with a high ponderal gain (from 60 to 110 g). However, independent of the date of gonadal arrest, the sexual activity of males spontaneously resumed at a fixed time after exposure to SD. The testes developed, testosterone concentrations increased to 155 nmol/l and the body weight decreased (from 110 to 80 g) within 20 weeks under SD exposure. The timing for refractoriness appeared very similar under inhibitory and stimulatory photoperiods. This is consistent with the hypothesis that the perception of a critical daylength is used to regulate the timing of the following sexual phase through a mechanism involving photorefractoriness. Contrary to cricetid rodents, a direct response to photoperiodic signals for both body weight and sexual activity were not prevented by olfactory bulb removal in male mouse lemurs. In bulbectomized males (n = 12), sexual activity was stimulated by LD and inhibited by SD. Their plasma testosterone levels, however, significantly differed from those of controls in both photoperiods. Likewise, ponderal cycles remained intact but the fattening phase was delayed and reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Effect of air pollution on olfactory function in residents of Mexico City.

To our knowledge there has been no study of the effect of everyday air pollution on olfactory function. It was therefore the aim of this study to compare the olfactory performance of long-term residents of Mexico City, an environment with high air pollution, with the olfactory performance of residents of the Mexican state of Tlaxcala, a region geographically similar to Mexico City but with low air pollution. Healthy volunteers [82 Mexico City subjects (MEX), 86 Tlaxcala subjects (TLX)] 20-63 years of age and balanced for age and gender between the two localities were tested for the perception of the odors of everyday beverages presented in squeeze bottles. When tested with ascending concentrations of stimuli in a three-way oddball paradigm, residents of Tlaxcala detected the odors of instant coffee and of an orange drink at significantly lower concentrations than residents of Mexico City. They also performed significantly better in discriminating between the two similar-smelling Mexican beverages horchata and atole in an oddball test. Significant differences between the two populations in overall olfactory performance were apparent in three of the four age classes (20- to 29-, 30- to 39-, and 40- to 49-year-old subjects) but not in the 50-63 years age class. About 10% of MEX subjects compared to about 2% of TLX subjects were judged to have poor olfactory function; all were from the older age classes (mean age: 48.6 years). Thus, air pollution in Mexico City appears to have a substantial impact on olfactory function even in young and middle-aged residents.

Adult↗
PubMed2004

Basic anatomy and physiology of olfaction and taste.

The chemical senses of taste and smell are important to survival and quality of life. Both senses rely on the binding of odorant molecules to receptors located on the receptor cells. Olfaction and gustation have complex systems of coding, but they display differing methods for coding the receptor stimulus. Both have numerous central projections that allow for the perception and interpretation of these important sensory inputs.

Chemoreceptor Cells↗
PubMed2001

Ethanol perception and ingestion.

Ethanol is a common dietary constituent, but knowledge of its chemosensory properties and their relationship to its ingestion is limited. Twenty-five male and 25 female, light-regular ethanol consumers participated in five test sessions. Sessions involved determination of taste, olfactory and nasal irritation thresholds for ethanol, taste thresholds for tetralone, suprathreshold intensity and quality judgements, determination of phenylthiocarbamide (PTC) taster status, acute oral exposure effect of ethanol on ratings for sucrose, NaCl, citric acid and quinine hydrochloride and hedonic judgments of beers. Questionnaires on personality traits, diet and health were also completed and body composition determined. Diet histories were obtained on three random days. A randomized subset of sensory tests and questionnaires were administered each session. The rank order of ethanol thresholds was taste>nasal irritancy>olfaction and the predominant taste near threshold was bitter. Except for a lower taste threshold in females, no other effects of gender, PTC taster status, ethanol use or body composition were observed. Acute exposure to ethanol suppressed the bitterness of quinine, but enhanced its bitter aftertaste. Ethanol use was not associated with differences in dietary, sensory or textural characteristics. Thus, among light to regular ethanol consumers, no substantive association was observed between sensory responses to ethanol and diet.

Adult↗
PubMed2005

The role of odor and irritation, as well as risk perception, in the setting of occupational exposure limits.

OBJECTIVE: This paper reviews current research regarding the relationship between odor perception or irritation and setting an occupational exposure limit (OEL). Special focus was directed at those settings where a small fraction of persons report unacceptable responses to concentrations well below the OEL. METHODS: We evaluated the published literature on the topic of irritation and olfactory response to exposure to industrial chemicals. More than a dozen researchers have been active in this area over the past 10 years. RESULTS: It was found that for some chemicals, even when one maintains airborne concentrations below a particular OEL, this level of exposure may not be adequate to prevent all persons from reporting an appreciable adverse response. In some cases, worker's pre-existing belief systems about the source of an odor may be sufficient to require that they have not be exposed to any detectable concentration. In addition, detection of odors by workers may tap into the person's aversion to odors, in general. In both situations, it is often necessary to address these specific issues through risk communication and dealing directly with risk perception. CONCLUSIONS: For practical reasons, the current objective of organizations charged with setting OELs for chemicals is to identify concentrations that do not cause irritation or widespread reports of unpleasant sensory stimulation in the vast majority of workers (e.g., about 80-95%).

Air Pollutants, Occupational↗
PubMed2007

The neural representation of odor is modulated by the presence of a trigeminal stimulus during odor encoding.

OBJECTIVES: Odor perception does not simply consist in hierarchical processing from transduction to a single "true" cerebral representation. Odor sensation may be modulated by available sensory information during encoding. The present study set out to examine whether the presence of a pure trigeminal stimulus during odor encoding may modulate odor perception at both behavioral and cortical levels. METHODS: Participants were tested in a 2-session within-subject design: first, an odor encoding session included a delay conditioning procedure in which relatively selective olfactory stimulants (phenyl ethyl alcohol or vanillin, Conditioned Stimulus+, CS+) were presented either with a pulse of CO(2) (Unconditioned Stimulus, US), or alone (Conditioned Stimulus-, CS-); then, in the second session, both pure odorants (CS+ and CS-) were presented alone. During this second session, olfactory event-related potentials were simultaneously recorded and analyzed at different electrode sites including Cz and Pz (sites known to have maximal amplitudes for trigeminal and olfactory stimuli, respectively). After each trial, subjects were asked to rate odor intensity and hedonics. RESULTS: The results showed that CS+ intensity ratings increased in 8 subjects and decreased in 6. Cortically, a group effect was observed for P2 amplitude, which increased in the "CS+ intensity increase" group vs. the "CS+ intensity decrease" group at Cz (p<0.05) but not at Pz (p>0.05). CONCLUSIONS: This result suggests that the presence of a pure trigeminal stimulus (CO(2)) during odor encoding alters the neural representation of a pure odor. SIGNIFICANCE: The neural representation of odors comprises not only the odor itself but also contextual information (trigeminal in the present case) presented during encoding.

Adult↗
PubMed2002

Bilateral and unilateral antennal lesions alter orientation abilities of the crayfish, Orconectes rusticus.

Numerous animals use chemical cues within their environments to execute various behaviors. One of these behaviors is orientation to an odor source. Crayfish, in particular, can orient to food sources under a number of different conditions. It has not been determined, however, what kind of search strategy these animals employ to successfully locate a food source. To determine the role of antennae and antennules in this behavior and to investigate different modes of orientation behavior, the orientation patterns of crayfish with complete and partial antennal lesions were examined. Detailed analysis of orientation paths confirmed that crayfish could not locate odor sources with either bilateral or unilateral lesions. This suggests that crayfish are using the spatial information obtained from these appendages to successfully orient. Animals using information from the bilaterally paired appendages in the control group exhibited increased walking speed, increased speed to source and decreased heading angles towards the source compared to these measurements taken from lesioned groups. There was no significant difference in any parameters between animals with unilateral or bilateral lesions. This strongly suggests that these animals are reliant on the spatial comparison of differences between bilaterally paired olfactory appendages for successful orientation.

Animals↗
PubMed1982

Olfactory and vomeronasal mediation of ultrasonic vocalizations in male mice.

The effects of deafferentation of the vomeronasal, olfactory or both systems of male mice on ultrasonic vocalizations in response to a male or female stimulus were analyzed. Regardless of the technique used, disruption of the vomeronasal system led to consistent reductions in ultrasonic vocalizations. Each animal receiving vomeronasal tract cuts, bulbectomies or a combined treatment of vomeronasal tract transection and intranasal flush with ZnSO4 markedly suppressed responding to the stimulus animals. Animals treated with intranasal ZnSO4 alone or those receiving control procedures continued to respond to the female stimulus animals at rates similar to pretreatment. These results indicate that the vomeronasal system is directly involved in the perception of female mouse chemosignals and, hence, mediates the male's responses to these signals.

Animals↗
PubMed1996

Responses of antennal olfactory receptors in the yellow fever mosquito Aedes aegypti to human body odours.

Recent behavioural studies have demonstrated that human body odours which female Aedes aegypti find attractive exert their effects as complex mixtures of synergistically acting components. We have attempted to clarify the sensory mechanisms underlying the perception of these complex host odours by studying the responses of sensory cells underneath the A3-type sensilla of the mosquito antenna to both a human skin wash extract and the extract's active chromatographic fractions. The reaction patterns show that the host stimuli elicit responses from several types of receptor cells in a typical across-fibre pattern mode. It seems as if this is another case where the essential message in a biologically significant odour consists of a complex pattern of compounds that is encoded in an according complex response pattern by a cooperating set of primary sensory neurons of different odour specificities.

Aedes↗