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PubMed2001

Acute anosmia in the mouse: behavioral discrimination among the four basic taste substances.

The importance of taste and smell in discrimination of tastes was examined in normal and anosmic mice. We studied the influence of olfaction on taste sensation using behavioral and electrophysiological methods in both normal animals and animals made anosmic mice by destroying their olfactory receptor cells with zinc sulfate (ZnSO(4)) solution. Electrophysiological responses from chorda tympani nerves showed that peripheral taste receptor cells transmitted taste signals normally to the central nervous system, even when the olfactory senses were abnormal. Behavioral observations showed that mice with abnormal olfaction could not differentiate tastes.

Animals↗
PubMed2001

A two-choice discrimination method to assess olfactory performance in pigtailed macaques, Macaca nemestrina.

Four pigtailed macaques were trained in a new two-choice olfactory discrimination method. They learned the initial task within 3 months, requiring a maximum of 900 trials. After the method was established, we investigated the olfactory threshold of three monkeys for the odors peanut, iso-amyl acetate, and n-pentanoic acid. The animals detected peanut odor in dilutions as low as 1:10000. They were able to perceive iso-amyl acetate up to a 30000-fold dilution (animals F1 and M2), respectively in a 30 Mio-fold dilution (animal M1). The sensitivity for n-pentanoic acid ranged between a dilution of 1:30000 (F1), 1:100000 (M2), and 1:300000 (M1). A comparison with the thresholds of other species demonstrates that the olfactory sensitivity of pigtailed macaques is not necessarily inferior to that of species that are believed to have a very keen sense of smell, such as dogs and rats. The sensitivity for certain odors seems to reflect their biological relevance for the tested species. The fact that the threshold for peanut odor obtained in this study is lower than the one found in a previous study with pigtailed macaques using a multiple olfactory discrimination method indicates that the new two-choice discrimination method is a better candidate for the assessment of olfactory abilities in pigtailed macaques.

Animals↗
PubMed2003

Assessment of the Sniff Magnitude Test as a clinical test of olfactory function.

Olfactory threshold and odor identification tasks currently serve as the standard approaches to the clinical assessment of olfactory function. Although these methods can be used effectively with the average patient, they suffer from some limitations when used to evaluate children, people with cognitive impairment, or people from diverse cultural backgrounds. A novel approach to the clinical evaluation of olfactory function, the Sniff Magnitude Test, attempts to minimize the cognitive demands of an olfactory test and thereby overcome some of the limitations of alternative tests. This is achieved by measuring the reflex-like reduction in sniffing that occurs when a malodor is encountered. The reliability and the validity of the Sniff Magnitude Test were assessed by testing people on two occasions using the University of Pennsylvania Smell Identification Test (UPSIT), a butanol threshold task, the Alcohol Sniff Test, and the Sniff Magnitude Test. The test-retest reliability of the Sniff Magnitude Test was r=.80, higher than the butanol thresholds and Alcohol Sniff Test but somewhat lower than the UPSIT. Performance on the Sniff Magnitude Test (the sniff magnitude to a malodor relative to nonodorized air) was correlated between r=-.61 and r=-.66 with the other measures of olfactory function. This range of correlations was comparable to that observed between the butanol threshold, the UPSIT, and the Alcohol Sniff Test. Finally, evidence for the advantages of the Sniff Magnitude Test, as compared to the UPSIT, was provided by a study with young children. It is concluded that the Sniff Magnitude Test has significant potential as a clinical measure of olfactory function, and that further testing and development of this method are warranted.

Adult↗
PubMed1997

Olfactory sensory-specific satiety in humans.

It is shown that olfactory sensory-specific satiety, measured by ratings of the pleasantness of the odour of a food eaten relative to the change in pleasantness of other foods, can be produced by eating a food to satiety. It is also shown that olfactory and taste sensory-specific satiety can be produced by chewing samples of a food for approximately as long as the food would normally be eaten in a meal. It is further shown that partial olfactory sensory-specific satiety can be produced by smelling the food for approximately as long as it would be in the mouth during a meal. These sensory-specific changes in the pleasantness of a food do not appear to reflect changes in the intensity of the foods, which were small and not highly correlated with the changes in pleasantness. The results show that at least partial olfactory, as well as taste, sensory-specific satiety does not require food to enter the gastrointestinal system, and does not depend on the ingestion of calories. The implications for the control of food intake, and the way in which the brain computes sensory-specific satiety, are considered.

Adult↗
PubMed1997

Olfaction in the domestic fowl: a critical review.

It has been known for some time that many species of birds, including domestic fowl Gallus domesticus, have an olfactory sense. However, the functional significance of avian olfaction is less clear. We review neurobiological, embryological and behavioral evidence relevant to the question of how domestic fowl use the sense of smell. Evidence suggests a potential role for olfaction in the formation of attachments to familiar objects or environments; in the elicitation of fear responses by alarm and predator-related odors; in the control of feeding and drinking; and in avoidance of noxious substances. The fact that domestic fowl can detect and respond to a wide range of odors, in a variety of behavioral contexts, has important practical implications, especially in relation to welfare and husbandry.

Animal Husbandry↗
PubMed1998

Chemosensory learning in the chicken embryo.

Prenatal chemosensory learning has been demonstrated in mammals, fish, amphibians, and insects, but not birds, although there is evidence of the avian's ability to learn auditory stimuli before hatching. This paper examines how exposure to a chemosensory stimulus (strawberry) prior to hatching affects subsequent chemosensory preferences of newly hatched chicks. The chicks' preferences were assessed at 2 days after hatching using an "olfactory" preference test (strawberry-smelling shavings versus water-coated shavings) and at 4 days after hatching using a "gustatory" preference test (strawberry-flavoured water versus unflavoured water). Chicken embryos were exposed to strawberry from Day 15 to Day 20 of incubation by either presenting the odour in the air around the egg, rubbing it onto the shell, or injecting it into the air space. With no exposure to strawberry before hatching, strawberry was highly aversive to chicks after hatching. However, following exposure to strawberry before hatching, chicks expressed a greater preference for (or weaker aversion to) the strawberry stimulus. Chicks exposed to strawberry before hatching drank more strawberry-flavoured water and spent more time in a strawberry-scented area than chicks having no exposure before hatching. This change in preference was specific to the stimulus experienced before hatching and was present in the absence of any posthatching exposure to the stimulus. The results demonstrate that a chick's chemosensory preferences are changed as a result of experience with a stimulus before hatching and are suggestive of learning. The results, similar to those obtained in other animal groups, indicate the universality of "prenatal" chemosensory learning in the animal kingdom. A possible role of embryonic chemosensory learning for recognition is discussed.

Animals↗
PubMed2001

Complexity of olfactory lateralization processes revealed by functional imaging: a review.

Currently available techniques used in neurosciences and particularly cerebral imaging are contributing to a better understanding of human perception and the treatment of sensorial information. In this field, the chemical senses (taste and smell) have received little attention when compared with the auditory, visual and tactile senses. Nevertheless, recent research has been trying to overcome this. Brain regions involved in the processing of olfactory information have been investigated in several studies including a large number dealing with the question of lateralization. However, functional asymmetry in olfaction has still not been resolved and the resulting data have not been homogeneous. In this field, the contribution of cerebral imaging studies is very important insofar as it shows that the processes of functional lateralization in olfaction depend on many factors (nature of stimulus, nature of task, characteristics of subjects ...) that future research will have to consider.

Animals↗
PubMed1999

Monorhinal odor identification and depression scores in patients with seasonal affective disorder.

BACKGROUND: Visual and olfactory pathways are interconnected. Olfactory deafferentation unmasks photoperiodic responsiveness in some nonphotoperiodic animals such as laboratory rats. By analogy, we hypothesized that olfactory deficits may unmask seasonal rhythms in certain individuals, namely those with seasonal affective disorder (SAD). Since previous studies suggest lateralized hemispheric dysfunction in SAD, and since olfactory neurons' primary projections are largely ipsilateral, we assessed olfactory identification performance on both the right and left side of the nose. METHODS: Twenty-four patients with SAD and 24 matched controls were studied using a phenyl ethyl alcohol detection threshold test bilaterally and the University of Pennsylvania Smell Identification Test unilaterally. Subjects rated their mood using the Self Assessment Mood Scale for SAD. Patients' testing was done in both 'depressed' and 'improved on light' states. RESULTS: No difference in olfactory performance was found between patients and controls or between patients before and after light treatment. However, right-side identification scores were negatively correlated with 'typical' depression scores (r = -0.56, P = 0.006), while left-side olfactory scores were not. Atypical depression scores were unrelated to olfactory performance. Similar correlations emerged between the olfactory identification laterality quotient (Right - Left)/(Right + Left) and typical depressive scores (r = - 0.64, P < 0.001) and total depression scores (r = - 0.59, P < 0.004). LIMITATIONS: We studied a demographically heterogeneous sample and did not control for menstrual factors. DISCUSSION: Our results add to previous evidence of lateralized hemispheric involvement in SAD and suggest that olfaction may be related to seasonal emotional rhythms in humans.

Adult↗
PubMed1998

Olfactory identification deficiency and WCST performance in men with schizophrenia.

Several studies using the University of Pennsylvania Smell Identification Test (UPSIT), which requires forced choice olfactory identifications, have reported olfactory identification deficits in patients with schizophrenia. This report examines the possible links between olfactory identification (usually attributed to the orbitofrontal cortex) and executive functions (usually attributed to dorsolateral prefrontal cortex) in 24 male patients with schizophrenia and 21 male comparison subjects. Olfactory performance was investigated under two conditions: spontaneous identification and forced choice identification. Executive function was assessed with the Wisconsin Card Sorting Test (WCST). Compared with controls, patients with schizophrenia exhibited a higher average number of cigarettes smoked per day, lower spontaneous identification scores on olfactory performance, and a higher percentage of perseverative errors on the WCST; there was a significant relationship between the two performance measures. Simpson-Angus scores, neuroleptic drug treatment levels, and scores on the Positive and Negative Syndrome Scale were not correlated with either olfactory measure. The lack of correlation between the forced choice olfactory identification score and the WCST score is consistent with findings in previous studies that used the UPSIT. By contrast, use of a spontaneous identification condition to assess olfactory performance did produce a significant association with WCST performance.

Adult↗
PubMed1999

Is odor processing related to oral breathing?

This paper addresses two questions related to the inherent association between breathing and odor perception: Does central nervous processing of odors change when an artificial breathing technique (velopharyngeal closure) is introduced and secondly, does odor processing vary with the oral breathing phase (inhalation or exhalation)? Chemosensory event-related potentials (CSERP) were obtained from eight female subjects while they were smelling an odor mixture (citral, eugenol, linalool, menthol and isoamylacetate). Each subject was required to perform spontaneous mouth breathing (120 trials) as well as the velopharyngeal closure technique (120 trials). Simultaneously, a thermistor monitored the phase of the respiratory cycle. The results reveal that the central nervous correlates of odor processing change with the breathing technique but not with the oral breathing cycle. The findings that early stimulus processing is faster (N1 latency) and late stimulus processing more pronounced (P3 amplitudes) when the subjects are breathing spontaneously are discussed with regard to attentional effects. The reduction of the N1 amplitude during the spontaneous breathing condition may be caused by larger latency variations and longer stimulus rise-times. Furthermore, it is concluded that the oral breathing cycle is less important than the nasal breathing cycle for olfactory information transmission.

Adult↗
PubMed1996

Anosmia and chronic sinus disease.

Chronic sinus disease associated with progressive mucosal disease is often a cause for anosmia. Despite aggressive allergic, medical, and surgical intervention, long-term relief of anosmia has been difficult to document. Fifty patients sought treatment for subjective anosmia and symptoms of progressive sinusitis and underwent endoscopic sinus surgery. After surgery 52% maintained significant improvement in smell by subjective measures that correlated with objective olfactory University of Pennsylvania Small Identification test ("UPSIT") results. Of the remaining patients, some had intermittent improvement, but most remained hyposmic or anosmic despite clinically well-healed ethmoid surgical beds. Of the preoperative and postoperative historical, clinical, and radiological data analyzed, severity of the presenting sinus disease (defined as stage II In the Kennedy staging criteria or disease extending beyond the ethmoids on preoperative computed tomography scan) and persistent mucosal disease in the surgical bed are associated with persistent anosmia (p = 0.005).

Adult↗
PubMed1979

A review of olfactory dysfunctions in man.

Although a large number of individuals experience olfactory disorders following accidents, disease states, medical interventions, aging, and exposure to environmental chemicals and pollutants, few medical practitioners have the expertise or staff to provide appropriate clinical evaluation, treatment, counseling, or referral for such patients. The present review examines studies associated with the diagnosis and treatment of olfactory disorders, as well as ones noting olfactory signs as diagnostic markers for brain tumors and other serious problems. A basic taxonomy of smell dysfunctions is presented, along with a review of etiologic factors, including local diseases and mechanical obstruction of the airways, viral infections, trauma, congenital anomalies, endocrine disorders, tumors, psychiatric disorders, aging, drugs, environmental and industrial pollutants, iatrogenic factors, and miscellaneous diseases. A discussion of current disability compensation guidelines in the United States and Britain is also presented.

Aging↗
PubMedDate not supplied

The human uses of olfaction.

The sense of smell may be important as an arousal system that calls attention to significant environmental events, air quality, and food. Humans share with animals an ability to store odor memories. The consequences of these memories include odor preferences and food aversions. Olfactory pheromones involved in sexual behavior have been observed in animals, but their existence in humans has not been proved.

Animals↗
PubMedDate not supplied

Identifying normosmics: a comparison of two populations.

An olfactory function test developed by the Connecticut Chemosensory Clinical Research Center (CCCRC) was administered to 65 normal subjects to determine its ability to identify normosmic subjects. The CCCRC test categorizes individuals into five distinct levels of olfactory functioning according to composite score ranges derived from odor identification and butanol threshold subtests. These categories are: normosmic (normal); mildly, moderately, and severely hyposmic (impaired functioning); and anosmic (no sensation). Comparing score distributions from CCCRC with ours revealed that a greater percentage of our subjects were categorized as hyposmic because of higher butanol thresholds. The butanol threshold subtest was studied further to determine test-retest reliability and normal day-to-day variability in scores. Norms are the basis for interpreting test scores and are important in diagnosing and treating smell disorders.

Adolescent↗
PubMedDate not supplied

Olfactory identification in elderly schizophrenia and Alzheimer's disease.

In the present study we assessed olfactory identification ability using the University of Pennsylvania Smell Identification Test (UPSIT) in 16 elderly patients with schizophrenia (ES), 20 patients with a diagnosis of probable Alzheimer's disease (AD), and 20 healthy elderly controls (EC). Both patient groups exhibited marked deficits in UPSIT performance relative to controls. ES and AD patients with similar levels of general cognitive impairment did not differ on the UPSIT, suggesting that the two disorders may share a common dysfunction in olfactory brain regions. While there have been recent reports of greater olfactory impairment in males, neither patient group exhibited significant gender differences on the UPSIT.

Aged↗
PubMed2003

Perceptual, affective, and cognitive judgments of odors: pleasantness and handedness effects.

The present study sought to examine the differential processing of pleasant, neutral, and unpleasant odors. The effects of the nostril stimulated (left or right) and the type of judgment (perceptual, affective, or cognitive) performed on the olfactory stimuli were also studied. To this end, 64 subjects were asked to smell pleasant, neutral, and unpleasant odors under four conditions (detection, intensity, pleasantness, and familiarity tasks). The participants were to perform these tasks as quickly as possible, while response times were recorded. The results showed that (i) unpleasant odors were assessed more rapidly than neutral or pleasant odors, and that this was specifically true (ii) during right nostril stimulation, and (iii) during pleasantness assessment, suggesting possible differential cerebral hemisphere involvement, with a right-side advantage for processing of unpleasant affect in olfaction. A handedness effect on familiarity judgment is also discussed.

Adult↗
PubMed2004

The functions of the orbitofrontal cortex.

The orbitofrontal cortex contains the secondary taste cortex, in which the reward value of taste is represented. It also contains the secondary and tertiary olfactory cortical areas, in which information about the identity and also about the reward value of odours is represented. The orbitofrontal cortex also receives information about the sight of objects from the temporal lobe cortical visual areas, and neurons in it learn and reverse the visual stimulus to which they respond when the association of the visual stimulus with a primary reinforcing stimulus (such as taste) is reversed. This is an example of stimulus-reinforcement association learning, and is a type of stimulus-stimulus association learning. More generally, the stimulus might be a visual or olfactory stimulus, and the primary (unlearned) positive or negative reinforcer a taste or touch. A somatosensory input is revealed by neurons that respond to the texture of food in the mouth, including a population that responds to the mouth feel of fat. In complementary neuroimaging studies in humans, it is being found that areas of the orbitofrontal cortex are activated by pleasant touch, by painful touch, by taste, by smell, and by more abstract reinforcers such as winning or losing money. Damage to the orbitofrontal cortex can impair the learning and reversal of stimulus-reinforcement associations, and thus the correction of behavioural responses when there are no longer appropriate because previous reinforcement contingencies change. The information which reaches the orbitofrontal cortex for these functions includes information about faces, and damage to the orbitofrontal cortex can impair face (and voice) expression identification. This evidence thus shows that the orbitofrontal cortex is involved in decoding and representing some primary reinforcers such as taste and touch; in learning and reversing associations of visual and other stimuli to these primary reinforcers; and in controlling and correcting reward-related and punishment-related behavior, and thus in emotion. The approach described here is aimed at providing a fundamental understanding of how the orbitofrontal cortex actually functions, and thus in how it is involved in motivational behavior such as feeding and drinking, in emotional behavior, and in social behavior.

Animals↗