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PubMed2006

[The human olfactory system. Anatomy and physiology].

The sense of smell is one of the phylogenetically oldest human senses. Nevertheless the number of publications regarding olfaction is marginal compared with other sensory systems. In recent years, however, there have been enormous advances in understanding the main olfactory processes. These range from the first contact of odorants with receptor cells in the nasal mucosa to the olfactory signal cascade to the processing of olfactory stimuli in the central nervous system. This article focuses on anatomy and physiology of the human sense of smell, which consists mostly of sensory input from two neural systems--the olfactory and trigeminal systems. It considers recent biomolecular experiments and functional neuroimaging studies in humans.

Humans↗
PubMed2003

Influences of ethanol ingestion on olfactory function in humans.

RATIONALE: Although ethanol is known to influence, in humans, psychophysical measures of visual, auditory, and vestibular function, the influence of this drug on the ability to smell is not clear. OBJECTIVES: To evaluate, in eight men and eight women, the influences of ethanol ingestion on four well-validated measures of olfactory function: an ethanol odor detection threshold test, a phenyl ethyl alcohol odor detection threshold test, a 40-item smell identification test, and an odor discrimination/short-term odor memory test. METHODS: In this double-blind experiment, grape juice alone was administered prior to the olfactory tests on one test occasion, and a grape juice-vodka mixture, designed to produce blood levels of ethanol near the legal level of intoxication, on another. The order of the two drug conditions was counterbalanced, as was the order of the presentation of the olfactory tests. RESULTS: Ethanol ingestion markedly influenced the detection threshold for ethanol (all 16 subjects exhibited higher thresholds under the ethanol than under the non-ethanol condition) and had a significant, albeit small, influence on odor discrimination performance, as measured by the total number of correct responses independent of delay interval. Women performed significantly better than men on the latter measure. No influences of ethanol on odor identification, the phenyl ethyl alcohol detection threshold, or the delay interval (memory) component of the odor discrimination/memory test were observed. CONCLUSIONS: Alcohol ingestion markedly and selectively alters olfactory sensitivity to ethanol, perhaps via habituation processes, and may subtly influence some measures of odor discrimination.

Adult↗
PubMed2004

Odor-induced changes in taste perception.

We investigated odor-induced changes in taste perception (OICTP), by examining the influence of strawberry and soy sauce odors on perceived sweetness (Experiment 1) and saltiness (Experiment 2). We explored whether taste-smell interactions occur at the central level, by delivering odorants (strawberry, soy sauce, odorless water) and tastants (sucrose, sodium chloride) separately, and whether effects of imagined odors are comparable to those of physically presented odors. We found specific taste-smell interactions: sweetness enhancement induced by strawberry odor and saltiness enhancement induced by soy sauce odor. These interactions were elicited with separate delivery of olfactory and gustatory stimuli. Secondly, we found a similar but rather limited effect with the imagined odors: imagined strawberry enhanced perceived sweetness of water solutions, and imagined soy sauce enhanced perceived saltiness of weak sodium chloride solutions. We concluded that OICTP is a centrally mediated phenomenon, and that imagined odors can to some extent induce changes in perceived taste intensity comparable to those elicited by perceived odors.

Adolescent↗
PubMed2004

Olfactory deficits in anorexia nervosa.

OBJECTIVE: Young patients admitted to the hospital due to anorexia nervosa report reduced pleasure and impaired perception of smell while eating. So far, two studies on odour identification ability in eating disorders did not suggest any significant deficits. Therefore a new and more detailed method of olfactory testing may be needed, in order to determine the subjective impairment of olfaction. METHOD: By using all three subtests of the recently developed smell test called "Sniffin'Sticks", the olfactory deficits were assessed in more detail and the results of female anorectic patients (n = 17) were compared with those of healthy females (n = 15). RESULTS: By examining the anorectic patients no deficits in the subtest odour identification were found. On the contrary, in the subtests odour discrimination and odour threshold deficits of the anorectic patients were detected. CONCLUSION: Reduced olfactory perception might be considered as a common deficit in anorexia nervosa with possible influences and consequences for therapy.

Adolescent↗
PubMed2005

Examination of the influence of personal traits and habituation on the reporting of complaints at experimental exposure to ammonia.

OBJECTIVE: The aim of the study is to examine the impact of personal traits and habituation on the intensity of self reported health symptoms and complaints. METHODS: Forty-three healthy male volunteers were exposed to ammonia vapours in concentrations of 0, 10, 20, 20/40, and 50 ppm on five consecutive days. To explore a possible influence of habituation on the perception of symptoms, the study group was divided into 30 men who were not familiar with the smell of ammonia, and ten participants regularly exposed to ammonia at the workplace. The perceived acute health symptoms and self-reported changes of well-being were assessed by the German version of a questionnaire of the Swedish Performance Evaluation System (SPES). Personal traits were ascertained with the positive and negative affectivity schedule (PANAS) and the Freiburger Persönlichkeits Inventar (FPI). RESULTS: There are significant associations between personal traits and the amount of complaints. Subjects with high positive affectivity report less respiratory and irritative complaints, whereas persons with negative affectivity report significantly more olfactory and respiratory symptoms. In general, the strength of these correlations decreases with higher exposure levels. At ammonia concentration above 20 ppm, these associations were no more statistically significant. During the daily exposures, the score of symptoms did not vary significantly. The perceived intensity of health symptoms and annoyance increased with the concentration of ammonia, while the self-reported dimensions of well-being decreased. Workers familiar with the smell of ammonia vapours reported less symptoms compared to naïve subjects. CONCLUSIONS: Habituation to ammonia vapours as well as personal traits influence the reporting of complaints particularly at low exposure. Both factors should be considered in the examination of chemosensory irritative compounds.

Adult↗
PubMed2005

Prevalence and risk factors for self-reported odour intolerance: the Skövde population-based study.

OBJECTIVES: The present study was performed to determine the prevalence of odour intolerance in adults with respect to both self-reported general intolerance and affective and behavioural consequences. Furthermore, we aimed to relate odour intolerance to explanatory variables and risk factors. METHOD: This is a cross-sectional, population-based epidemiological study. A random sample of 1900 inhabitants from the age of 20, stratified for age and gender, were recruited. Subjects were invited for clinical examinations that included questions about general odour intolerance, respiratory symptoms and smoking habits, as well as a smell identification test. The chemical sensitivity scale for sensory hyperreactivity (CSS-SHR) was used to quantify affective and behavioural consequences. RESULTS: In total 1387 volunteers (73% of the sample) were investigated. The overall prevalence of self-reported general odour intolerance was 33% (95% confidence interval (CI): 30-36%), with problems mainly from the upper respiratory tract. The prevalence of affective and behavioural consequences of odour intolerance (CSS-SHR score > or =43) was 19% (95% CI: 15-22%). The risk for the latter condition was increased in women compared with men (odds ratio = 2.3: 95% CI: 1.5-3.6), but no increased risk was found related to current smoking or impaired sense of smell. CONCLUSION: This study demonstrates that intolerance to odours is a widespread problem in society, and that it is about twice as common in women than in men.

Adult↗
PubMed1999

Assessing olfaction in the Italian population: methodology and clinical application.

Disorders of the sense of smell are receiving growing clinical as well as experimental attention. Indeed, several neurological conditions have been associated with peripheral or central deficits of the olfactory system. In recent years, particular emphasis has been attributed to the early and severe olfactory impairment in neurodegenerative diseases, such as Alzheimer's dementia and Parkinson's disease. Olfactory assessment has also been included in comprehensive pre- and post-surgical evaluations of temporal lobe epilepsy. Moreover, the request for standardized methods of olfactory evaluation by forensic and occupational medicine is greatly increasing. Despite this requirement, there is no agreement in the Italian neurological community on olfactory assessment. This lack prompted us to generate a battery of standardized tests capable of bypassing cross-cultural differences in olfactory assessment and to be potentially useful in the clinical as well as experimental settings. Procedures of assessment of olfactory acuity (detection threshold), identification (multiple choice odor naming), discrimination (differentiation between similar/dissimilar odorants) and memory (recognition of a substance previously smelled) are fully described. In order to control bias factors depending upon the nature of the investigated disorder and the applied olfactory tasks, a minimal complementary neuropsychological assessment is recommended.

Humans↗
PubMed1995

Respiratory learning and somatic complaints: a conditioning approach using CO2-enriched air inhalation.

In a differential respiratory conditioning paradigm with normal Ss two odors (fresh smelling niaouli and bad smelling ammonia) were used as conditioned stimuli (CS+ or CS-) and 7.4% CO2-enriched air was used as the unconditioned stimulus (US). Three CS+ and three CS- trials were run during acquisition, followed on the next day by the same number of CS+ and CS- only trials. Respiratory frequency, minute ventilation, end-tidal fractional concentration of CO2 and subjective complaints were measured throughout the experiment. While during acquisition all measures were affected, the conditioning effects included only respiratory frequency and subjective complaints. A selective association effect appeared in that the conditioning effects were confined to ammonia as CS+: respiratory frequency increased and more somatic complaints were presented when compared to the CS- condition. The conditioning effect on complaints was not confined to complaints of general arousal, but included respiratory complaints as well. Correlational analyses showed that increases in complaints as caused by the conditioning procedure were predicted by changes in somatic variables, but not by individual differences in Negative Affectivity.

Adolescent↗
PubMed1995

Olfactory identification ability in pre- and postmenopausal women with schizophrenia.

Previously we reported olfactory deficits in young male but not female patients with schizophrenia. In the present report, olfactory identification ability in pre- and postmenopausal women with schizophrenia and normal control subjects was assessed using the University of Pennsylvania Smell Identification Test (UPSIT). Additionally, serum estradiol levels were measured on the same 2 days as smell testing was completed. Olfactory deficits were observed in pre- and postmenopausal women with schizophrenia but were more pronounced in the postmenopausal patients. Regarding estradiol levels, women with schizophrenia had lower estradiol levels than did normal control subjects. The findings of this study indicate that olfactory deficits do exist in women with schizophrenia and may be accentuated by estrogen depletion.

Adult↗
PubMed1996

Neuropsychological, olfactory, and hygiene deficits in men with negative symptom schizophrenia.

Associations between symptom subtypes, life skills, olfactory identification, and neuropsychological ability were investigated in patients with schizophrenia and related to observations of poor personal hygiene and implied functional compromise of orbitofrontal integrity. Twenty-seven men with chronic schizophrenia were assessed using the Positive and Negative Syndrome Scale for Schizophrenia and the Life Skills Profile. Performance on the University of Pennsylvania Smell Identification Test (UPSIT), the Modified Wisconsin Card Sorting Test (MWCST), delayed response/alternation, and memory tasks derived from the Wechsler Memory Scale-Revised (WMS-R) was also compared to that of an age-, sex-, and IQ-matched control group. Patient UPSIT, MWCST, and WMS-R performance was significantly impaired in comparison to controls. Poor UPSIT performance and poor self-care were significantly associated with negative symptoms. Also, UPSIT ability was associated with performance on the MWCST in both patients and controls, whereas an association with performance on the WMS-R was only found in normal subjects rather than in the patients with schizophrenia. The importance of these findings to postulated mechanisms involving prefrontal rather than mediotemporal lobe (MTL) function in schizophrenia are discussed, as is the relevance of the use of smell identification ability to subtype identification and rehabilitative strategies.

Activities of Daily Living↗
PubMed1982

Flavor-toxicosis associations: tests of three hypotheses of long delay learning.

Rats were prepared with gastric cannulas and esophageal fistulas to assess the contribution of taste and smell, postingestinal stimuli, and the combination of the two in forming flavor-toxicosis associations. Groups were either given sugar water to drink, a stomach intubation of sugar water, both sugar water to drink and a stomach intubation of sugar water, or not given sugar water. The experimental and pseudo-conditioning control animals were given a LiCl injection and the control animals were given a NaCl injection one hour later. They were tested for drinking of sugar water the next day. It was found that taste and smell are the primary stimuli for forming food aversions. Furthermore, postingestional stimuli are not sufficient to produce this type of learning.

Animals↗
PubMed1983

The olfactory detection of sodium and lithium salts by sodium deficient cattle.

With development of Na+ depletion in cattle enhancement in the specific ability to smell very low concentrations of salt occurs. At the same time a behaviour pattern develops, in which increased locomotory activity is seen, directed towards searching for sodium salts. Following the initial successful location of a sodium source the pattern once learned, is consolidated by repetition and by consummation of the salt reward. Our data shows that olfactory and gustatory receptors are able to detect minute amounts of sodium salts as biochemical disruption develops with Na+ depletion but the central input from smell and taste receptors remain distinct. Salt appetite does not appear to be pleasurable (hedonic) in cattle, for salt appetite which is a feature of Na+ depletion does not persist when the ionic deficit is restored. The innate behaviour which develops with increased salt appetite in cattle may account for the evolutionary success and worldwide distribution of ruminants.

Animals↗
PubMed1986

Olfactory acuity in the common raven (Corvus corax).

The efficacy with which ravens can locate concealed carrion and similar foods has been noted from antiquity. This ability has been claimed in folklore to indicate an acute sense of smell. Contemporary opinion among ornithologists is that the sense of smell is weak at best in passerines, and particularly so in corvids which lack developed olfactory apparatus. Four studies were performed to test whether ravens could find hidden food (fresh ground fish) under conditions where scent was presumed to be the sole cue. The subjects, captive juvenile ravens (five males and three females) capably chose which one in a pair of containers held food buried under 2.0 cm of No. 4 gravel, discovered food concealed under as much as 2.5 cm of gravel, and located as little as 1.0 g of food covered by 1.5 cm of gravel. The several findings are consistent with the possibility that ravens can use olfactory cues to find food.

Animals↗
PubMed1991

Nasal pungency, odor, and eye irritation thresholds for homologous acetates.

We measured detection thresholds for nasal pungency (in anosmics), odor (in normosmics) and eye irritation employing a homologous series of acetates: methyl through octyl acetate, decyl and dodecyl acetate. All anosmics reliably detected the series up to heptyl acetate. Only the anosmics without smell since birth (congenital) reliably detected octyl acetate, and only one congenital anosmic detected decyl and dodecyl acetate. Anosmics who lost smell from head trauma proved to be selectively less sensitive. As expected, odor thresholds lay well below pungency thresholds. Eye irritation thresholds for selected acetates came close to nasal pungency thresholds. All three types of thresholds decreased logarithmically with carbon chain length, as previously seen with homologous alcohols and as seen in narcotic and toxic phenomena. Results imply that nasal pungency for these stimuli rests upon a physical, rather than chemical, interaction with susceptible mucosal structures. When expressed as thermodynamic activity, nasal pungency thresholds remain remarkably constant within and across the homologous series of acetates and alcohols.

Acetates↗
PubMed1985

Dysosmia and dysgeusia presenting as depression.

Disorders of taste and smell are underrecognized and often misdiagnosed. Two cases are described in which patients mistakenly thought to suffer from depression actually had unnoticed drug-induced dysosmia and dysgeusia. Also reviewed are psychiatric, neurologic, and medical disorders and drugs that cause abnormalities of taste and smell, and some behavioral aspects of food aversions. Three groups, all of whom may superficially appear depressed, must be distinguished from each other: 1) patients with dysosmia or dysgeusia, 2) patients with primary neuropsychiatric illness with olfactory or gustatory hallucinations, and 3) patients with conditioned taste aversions.

Aged↗
PubMed1995

Reasons for non-drinking among Israeli adolescents of four religions.

Adolescent abstainers have largely been ignored in the literature. This article describes the reasons for not drinking of 2366 Israeli Jewish, Moslem, Druze and Christian adolescents in the north of Israel in the winter of 1994. It analyzes the findings by religious group, religiosity (secular versus religious Jews), location and gender of Jews, and school grade of Jews and Moslems. Harmful health consequences of alcohol use and religious injunction are the most prevalent reasons for abstinence among Moslems and Druze. Jews abstain mainly because of disliking the taste and/or smell of alcohol and because they 'do not care for it'. Christians abstain mainly because of the harmful effects of alcohol on health and dislike of its taste and/or smell. The implications of the results for prevention are discussed.

Adolescent↗
PubMed2005

Human pheromones and sexual attraction.

Olfactory communication is very common amongst animals, and since the discovery of an accessory olfactory system in humans, possible human olfactory communication has gained considerable scientific interest. The importance of the human sense of smell has by far been underestimated in the past. Humans and other primates have been regarded as primarily 'optical animals' with highly developed powers of vision but a relatively undeveloped sense of smell. In recent years this assumption has undergone major revision. Several studies indicate that humans indeed seem to use olfactory communication and are even able to produce and perceive certain pheromones; recent studies have found that pheromones may play an important role in the behavioural and reproduction biology of humans. In this article we review the present evidence of the effect of human pheromones and discuss the role of olfactory cues in human sexual behaviour.

Animals↗
PubMed2005

Stimuli inducing gregarious colouration and behaviour in nymphs of Schistocerca gregaria.

Solitarious nymphs of Schistocerca gregaria were reared under various conditions in both Jerusalem and Oxford to tease apart cues involved in behavioural and colour phase change. Treatments included rearing nymphs from the IInd or IIIrd until the final nymphal stadium in physical contact with similarly aged conspecific groups or with another locust species, Locusta migratoria migratorioides, as well as confining single nymphs in mesh cages, which were kept within crowds of S. gregaria or L. migratoria migratorioides, providing visual and olfactory but no physical contact with other locusts. In the Oxford experiments, an extra treatment was included which provided olfactory cues without visual or contact stimulation. Our results confirm that transformation from the solitarious to the gregarious phase of locusts is complex, and that different phase characteristics not only follow different time courses, but are also controlled by different suites of cues. As predicted from earlier studies, behavioural phase change was evoked by non-species-specific cues. Rearing in contact with either species was fully effective in inducing gregarious behaviour, as was the combination of the sight and smell of other locusts, but odour alone was ineffective. Colour phase change was shown to comprise two distinct elements that could be dissociated: black patterning and yellow background. The former of these could be induced as effectively by rearing S. gregaria nymphs in a crowd of L. migratoria migratorioides as by rearing with conspecifics. Sight and smell of other locusts also triggered black patterning and, unlike behavioural change, some black patterning was induced by odour cues alone. Hence, physical contact was not needed to induce gregarious black patterning. Yellow colouration, however, was only fully induced when locusts were reared in contact with conspecifics, implying the presence of a species-specific contact chemical cue.

Analysis of Variance↗