SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
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.
Explore the source record for details and available documents.
Over the last fifteen years, we have witnessed a rapid expansion in the development of artificial odour sensing systems, or so called 'electronic nose' systems. Whilst the power of this approach to flavour has undoubtedly been demonstrated by its recent application to various complex odours, it will be argued that the original research programme, aimed at developing a comparative model of the biological olfactory pathway, has degenerated into an attempt to obtain an ad hoc workable system, based around readily available sensor and pattern recognition (PARC) technologies. At the time, the first 'model' nose system reflected the limited understanding of sensory information processing carried out within the biological olfactory pathway. We are now presented with an opportunity to evaluate and re-assess the architecture for an electronic nose, in view of the recent advances in understanding the key processing principals exploited by the olfactory bulb and cortex in the identification and characterisation of molecular stimuli. In Part II of this paper, we examine the parallels that exist between the biological olfactory system and the electronic nose. It is shown that the two systems share many similarities in their architectures and other properties, such as odour delivery, nonspecific sensor/receptor response, sensor/receptor preprocessing and content addressable memory (CAM) function. Of particular importance, both systems need to overcome similar operating problems, such as sensor/receptor drift, degeneration and poisoning, limited sensor/receptor sensitivity, discrimination of odour quality invariant of intensity and also the identification of particular odour components within a mixture of background odours. Finally, a number of opportunities for improving the biological plausibility of electronic nose systems are suggested that may yield an improvement in performance.
Rats were initially trained on a series of odor detection tasks and then received a unilateral olfactory bulbectomy and removal of different parts of the contralateral bulb. After postoperative recovery they were tested for detection of different concentrations of four odors, on a series of odor discrimination tasks and for their ability to acquire a relatively easy and a more difficult odor mixture discrimination task. Groups were formed based on which region of the bulb was intact (regional savings score) and on amount of bulb intact (bulbar savings score). In general, only rats with bulbar savings scores of less than 21% had deficits in detection or discrimination tasks but most performed as well as controls in most tasks. Correlations between bulbar savings scores and error scores were relatively low across all rats but, within the subgroup with the largest lesions (bulbar savings scores <21%), high correlations between these variables were obtained. There was no evidence for a specific anosmia in any group or individual rat and, except for the more difficult odor mixture discrimination, no one task proved difficult for any subgroup. The present results demonstrate that rats with relatively small remnants of one olfactory bulb can perform a variety of odor detection and discrimination tasks as well or nearly as well as controls. These outcomes provide no support for localization of function within the olfactory bulb but are in accord with recent proposals that odors may be coded by a highly distributed pattern of bulbar input.
Oral health, taste, and smell are critical components to an older person's overall sense of well-being and quality of life. Oral health problems can cause pain and discomfort and can hinder the maintenance of a satisfying and nutritious diet. Loss of taste and smell interferes with pleasure derived from food and food-related activities. Attention should be given to preserving teeth and optimizing oral function. Likewise, close evaluation of older adults' medications may identify the causes of taste and smell disorders. In instances in which nutrient intake is inadequate and chemosensory perception is considered a likely contributor, a trial of flavor enhancers or monosodium glutamate may improve both quality and quantity of intake. Much more information is needed to understand the interrelationship between chemosensory perception, food intake regulatory mechanisms, and nutritional status. Multidisciplinary studies will be required to understand how to improve nutrition through manipulation of oral characteristics, taste, and smell.
Magnetic field changes were recorded while 20 healthy young participants performed a deep face encoding task. Some of the faces were randomly associated with a simultaneously presented odor. A recognition test, during which all faces were presented again together with the same number of new faces, followed. The task was to discriminate between repeated and new faces. During the recognition test no odor was presented. The recognition performance was significantly influenced by the simultaneously associated odor during the encoding phase. Faces associated with odor were less accurately recognized. In addition, we found significant physiological differences between 'encoded faces without odor' and 'encoded faces with odor'. In particular, two effects occurred. Between about 200 and 300 ms after stimulus onset 'encoded faces without odor' evoked higher brain activity than 'encoded faces with odor'. Between about 600 and 900 ms after stimulus onset 'encoded faces with odor' evoked higher brain activity than 'encoded faces without odor'. Whereas the latter effect is interpreted as reflecting conscious olfactory information processing, the earlier effect is suggested to reflect an odor influence on face encoding. We suggest that the simultaneous odor association distracted face encoding resulting in a significantly reduced recognition performance. These findings are suggested to represent evidence of multimodal sensoric interactions between visual face processing and olfactory information.
Recent experiments in Drosophila demonstrate striking stereotypy in the neural architecture of the olfactory system. Functional imaging experiments in mammals and honeybees suggest a mechanism of odor coding that translates discrete patterns of activity in olfactory glomeruli into an odor image. Future experiments in Drosophila may permit a direct test of this odor-coding hypothesis.
An olfactory sensory neuron most probably expresses a single olfactory receptor gene, out of 1000 choices. Olfactory neurons expressing the same olfactory receptor are distributed over a wide area of the olfactory epithelium, but they project their axons to a few discrete positions in the olfactory bulb, out of 2500 choices. How?
Expression of a receptor protein has, for the first time, been definitively correlated with sensitivity to a particular odorant. This receptor, expressed in the nematode Caenorhabditis elegans, appears to be distinct from the putative vertebrate odorant receptors.
The present study investigated activation of distinct cerebellar regions as a result of olfactory stimulation in healthy young and elderly adults using functional magnetic resonance imaging (fMRI). Ten young and 10 elderly adults were imaged using a 1.5-TMR scanner. The odorant amyl acetate was delivered in 12-s on, 40-s off cycles. Throughout the scan participants responded with a button press at first detection of each stimulus interval followed by a second button press upon odorant extinction. Images were processed with AFNI software. Elderly participants showed significantly decreased cerebellar activation in both the superior semilunar lobule (Crus I) and the inferior semilunar lobule (Crus II), two of three previously identified regions of interest for odor processing, compared to young adults. Interestingly, both groups showed similar levels of activation in the third region of interest, the posterior quadrangular lobule (VI), although the elderly showed more variability than the young did. Previous research identifying this area to be involved in attention may reflect the possibility that elderly adults engaged in olfactory tasks may show more variability than young participants in the degree of attentional demands needed for these tasks as a result of decreased olfactory abilities.
BACKGROUND: Previous research has established a relationship between smell identification deficits (SID) and particular aspects of cognitive function among patients with schizophrenia. OBJECTIVE: To expand the extant literature, we examined the relationship between SID and the Trail Making Test to determine if processing speed is related to SID. METHODS: Our sample included 60 inpatients from the New York State Psychiatric Institute's Schizophrenia Research Unit. We considered age, deficit syndrome, verbal intelligence quotient, and education in our analyses due to their documented relationship to smell identification ability. RESULTS: Trails A errors and Trails A seconds accounted for a significant amount of the variance in University of Pennsylvania Smell Identification Test scores in a regression analysis (R2=.10, P=.008 and R2=.05, P=.04). CONCLUSION: Linking neurocognition to smell identification deficits may prove to be an essential marker for schizophrenia research.
High-density sensor arrays were prepared with microbead vapor sensors to explore and compare the information coded in sensor response profiles following odor stimulus. The coded information in the sensor-odor response profiles, which is used for odor discrimination purposes, was extracted from the microsensor arrays via two different approaches. In the first approach, the responses from individual microsensors were separated (decoded array) and independently processed. In the second approach, response profiles from all microsensors within the entire array, i.e., the sensor ensemble, were combined to create one response per odor stimulus (nondecoded array). Although the amount of response data is markedly reduced in the second approach, the system shows comparable odor discrimination rates for the two signal extraction methods. The ensemble approach streamlines system resources without decreasing system performance. These signal compression approaches may simulate or parallel information coding in the mammalian olfactory system.
Explore the source record for details and available documents.
Georgyone (1) and arborone (2), powerful woody odorants, have been synthesized enantioselectively along with their enantiomers. Several structural relatives of 1 and 2 have also been made enantioselectivity in order to probe the molecular details of the binding of 1 and 2 to the olfactory G-protein-coupled receptors which they activate. These studies have led to a number of conclusions regarding the structural requirements for woody odor, including absolute configuration, critical methyl substitution, and the spatial orientation of the key methyl groups. Odorants 1 and 2 bind to at least 10 mouse olfactory receptors, lending support to the combinatorial model for odor perception/differentiation. The implications of this work with regard to possible receptor binding modes are discussed.
Explore the source record for details and available documents.
Single-unit electrophysiology was used to record the nerve impulses from the carbon dioxide receptors of female Queensland fruit flies, Bactroera tryoni. The receptors responded to stimulation in a phasic-tonic manner and also had a period of inhibition of the nerve impulses after the end of stimulation. at high stimulus intensities. The cell responding to carbon dioxide was presented with a range of environmental odorants and found to respond to methyl butyrate and 2-butanone. The coding characteristics of the carbon dioxide cell and the ability to detect other odorants are discussed, with particular reference to the known behavior of the fly.
The electroantennogram method was used to investigate the number of distinct olfactory receptor neuron types responding to a range of behaviorally active volatile chemicals in gravid Queensland fruit flies, Bactrocera tryoni. Three receptor neuron types were identified. One type responds to methyl butyrate, 2-butanone, farnesene, and carbon dioxide; a second to ethanol; and a third to n-butyric acid and ammonia. The receptor neuron type responding to methyl butyrate, 2-butanone, farnesene, and carbon dioxide consists of three subtypes. The presence of a limited number of receptor neuron types responding to a diverse set of chemicals and the reception of carbon dioxide by a receptor neuron type that responds to other odorants are novel aspects of the peripheral olfactory discrimination process.
Humans, like other mammals, are capable of discriminating between kin and non-kin by olfactory cues alone. Shortly after birth, breastfed infants become familiar with, and respond preferentially to, their mother's unique odor signature. Mothers likewise recognize the characteristic scent of their newborn infant. Close biological relatives share somewhat similar odor signatures (presumably resulting from genetically mediated similarities in bodily biochemistry and metabolism) that could facilitate kin recognition.