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PubMed2003

Sense of smell: recognition and transduction of olfactory signals.

The primary processes in odour perception, i.e. recognition and transduction of olfactory stimuli, are mediated by the chemosensory olfactory neurons. Interaction of odorous compounds with suitable receptor proteins in the membrane of a subset of cells elicits chemo-electrical transduction pathways, including second messenger cascades and ion channels, that modulate the excitability of the sensory neurons, i.e. converting the chemical stimulus into electrical impulses. The encoded information is conveyed via the axons onto distinct glomeruli in the olfactory bulb. Olfactory sensory cells expressing the same receptor type are segregated spatially in a distinct zone of the nasal epithelium and converge their axons to one or a few distinct glomeruli. The emerging chemotopic maps are considered to be crucial for processing and encoding sensory information of olfactory stimuli.

Animals↗
PubMed1995

Smell and taste classification of the same stimuli.

Although it has long been known that the perception of flavor depends on olfactory sensations originating within the mouth (i.e., retronasal perception), little is known about how olfactory input is integrated in the flavor complex. In the present study, the qualitative contribution of odor to flavor was explored. Participants judged the smell and taste of pairs of substances (liqueurs). Each set of judgments was analyzed by means of multidimensional scaling, and the scalings were then statistically compared. The results revealed specific perceptual dimensions, namely, sweet-sour, harsh-mellow, which underlie both sensory modalities. In contrast to previous findings, the results show that the characteristics of flavor reflect olfactory attributes that can be apprehended outside the mouth.

Adult↗
PubMed2003

Olfactomotor activity during imagery mimics that during perception.

Neural representations created in the absence of external sensory stimuli are referred to as imagery, and such representations may be augmented by reenactment of sensorimotor processes. We measured nasal airflow in human subjects while they imagined sights, sounds and smells, and only during olfactory imagery did subjects spontaneously enact the motor component of olfaction--that is, they sniffed. Moreover, as in perception, imagery of pleasant odors involved larger sniffs than imagery of unpleasant odors, suggesting that the act of sniffing has a functional role in creating of olfactory percepts.

Auditory Perception↗
PubMed2005

Perception without a thalamus how does olfaction do it?

The olfactory system has generated considerable interest in recent years, mainly focused on receptor genes and early olfactory processing. In this issue of Neuron, Mori et al. focus centrally, providing evidence for slow- and fast-wave states in olfactory cortex that appear to gate the inflow of information underlying conscious smell perception.

Olfactory Bulb↗
PubMed2006

Broad activation of the olfactory bulb produces long-lasting changes in odor perception.

A number of electrophysiological experiments have shown that odor exposure alone, unaccompanied by behavioral training, changes the response patterns of neurons in the olfactory bulb. As a consequence of these changes, across mitral cells in the olfactory bulb, individual odors should be better discriminated because of previous exposure. We have previously shown that a daily 2-h exposure to odorants during 2 weeks enhances rats' ability to discriminate between chemically similar odorants. Here, we first show that the perception of test odorants is only modulated by enrichment with odorants that activate at least partially overlapping regions of the olfactory bulb. Second, we show that a broad activation of olfactory bulb neurons by daily local infusion of NMDA into both olfactory bulbs enhances the discrimination between chemically related odorants in a manner similar to the effect of daily exposure to odorants. Computational modeling of the olfactory bulb suggests that activity-dependent plasticity in the olfactory bulb can support the observed modulation in olfactory discrimination capability by enhancing contrast and synchronization in the olfactory bulb. Last, we show that blockade of NMDA receptors in the olfactory bulb impairs the effects of daily enrichment, suggesting that NMDA-dependent plasticity is involved in the changes in olfactory processing observed here.

Animals↗
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↗
PubMed2003

Olfactory mucosa histological findings in laryngectomees.

After total laryngectomy, the patients often report immediate and marked olfactory deficit. The aim of this study was to determine whether hyposmia in laryngectomees reflects olfactory epithelial damage. Ten laryngectomized patients and ten rhinologically normal subjects were subjected to olfactory testing, after which histological examination of biopsied olfactory mucosa was performed. Olfactory testing in laryngectomees revealed a marked reduction in odor perception. Histological examination of olfactory mucosa specimens showed that in laryngectomees some neuroepithelial structural features were comparable with those found in normal subjects. However, additional signs of damage were also observed, consisting mainly of various degrees of epithelial degeneration, above and beyond those that are characteristic of physiological epithelium turnover. These different degenerative features consisted of severe damage to the neuroepithelium, culminating in complete topical loss. Bowman's glands were also observed to be involved in the degenerative process. Laryngectomy-induced hyposmia seems to be correlated with the almost complete loss of nasal airflow due to the disconnection between the upper and lower airways, which prevents odor molecules from reaching the olfactory area, together with degenerative phenomena, which affect the neuroepithelium, and consequent failure in neurosensorial performance.

Aged↗
PubMed1999

Depressed taste and smell in geriatric patients.

BACKGROUND: Geriatric patients have a number of dental care problems that younger patients do not encounter. The oral changes associated with aging can have a significant effect on the efficacy of dental treatment. TYPES OF STUDIES REVIEWED: The authors reviewed studies dealing with the causes of depressed sense of taste and smell; the causes included aging, disease, medications and dental problems. Based on their findings, the authors described the location and anatomy of taste buds and receptor cells for smell and explored appetite, saliva, food seasonings, nutrition and dietary recommendations. They also discussed the relationship of smoking and tongue cleaning to taste sensations. RESULTS: The authors found that considerable differences exist between elderly people and young people in regards to sensory perception and pleasantness of food flavors. Salt and bitter taste acuity declines with age, but sweet and sour perceptivity does not. Olfactory acuity also declines with age. The authors found that most of the studies reviewed suggested that the sense of smell is more impaired by aging compared with the sense of taste. Smoking diminishes the taste of food and makes flavorful foods taste flat, while tongue brushing can increase taste sensation for geriatric patients. CLINICAL IMPLICATIONS: Food can become tasteless and unappetizing for geriatric patients as the result of declining taste and smell perception. Geriatric patients should be encouraged to add seasonings to their food instead of relying on excessive consumption of salt and sugar to give their food flavor. Adequate nutrition, tongue cleaning and smoking cessation are recommended for geriatric dental patients.

Aged↗
PubMed1996

Synthesis and future challenges: the response of mosquitoes to host odours.

There is ample evidence that host seeking in mosquitoes is mediated by semiochemicals emanating from the host. Olfactory cues (kairomones) are detected through an intricate pathway, beginning with sensilla located on the antennae (odour) and palpi (CO2). Age and physiological state of the mosquito determine whether detection of kairomones results in a behavioural response. Only a few kairomones have been described so far. CO2 is a kairomone for most mosquito species and signifies the presence of a potential host because of its occurrence in the volatile emissions of all vertebrates. Other chemicals are likely to play a role in mosquito-host interaction as well, notably L-lactic acid, fatty acids and 1-octen-3-ol. Species-specific host preference is thought to be olfactory based and related to the presence of specialized sensilla or perception at the central olfactory pathway. Host specificity is genetically determined, as demonstrated by inherited differences within members of the Anopheles gambiae complex. In view of the available evidence, challenging research areas are: (1) the function of olfactory receptors and the level of specialization; (2) the identification of general and host-specific kairomones; (3) demonstration of behavioural responses to laboratory-identified olfactory cues in the field; (4) studying whether mosquito host-locating behaviour can be manipulated by kairomones; (5) the genetics of the regulation of olfactory behaviour; and (6) determining whether there is an olfactory basis for the evolution of mosquito-host interactions.

Animals↗
PubMed2006

Cortical contributions to olfaction: plasticity and perception.

In most sensory systems, the sensory cortex is the place where sensation approaches perception. As described in this review, olfaction is no different. The olfactory system includes both primary and higher order cortical regions. These cortical structures perform computations that take highly analytical afferent input and synthesize it into configural odor objects. Cortical plasticity plays an important role in this synthesis and may underlie olfactory perceptual learning. Olfactory cortex is also involved in odor memory and association of odors with multimodal input and contexts. Finally, the olfactory cortex serves as an important sensory gate, modulating information throughput based on recent experience and behavioral state.

Animals↗
PubMed2005

Distorted perception of smell by volatile agents facilitated inhalational induction of anesthesia.

BACKGROUND: Unpleasant smell of halogenated volatile agents is one of the frustrating factors for inhalational induction. We developed a new modification that might enable children to enjoy the smell itself while incrementally elevating sevoflurane concentration. Troposmia is usually a pathological quality change of smell perception and an olfactory stimulus is distortedly perceived in this state, which we applied to inhalational induction. METHODS: At the preoperative visit an anesthetist told the children that the smell of a facemask could be magically changed from strawberry into anything and promised to change the smell as they requested. In the operating room, a strawberry scented facemask was fitted to the face and the anesthetist announced to them that the magical change of the smell would begin when sevoflurane was added. Whether children perceived the change of the smell as they requested was investigated in the troposmia group, and resistance to fit a facemask was compared between the troposmia group and a control group. RESULTS: Significantly fewer children resisted the facemask in the troposmia group (1 of 32 vs 9 of 32; P = 0.0059). In the troposmia group 18, 22 and 25 of the 32 children said the smell of the facemask changed as they requested before they fell asleep, at the postoperative visit or both, respectively. CONCLUSIONS: Troposmia can be intentionally induced to perceive the smell of sevoflurane on request. Troposmia might contribute to promote children's participation in anesthesia induction and facilitate inhalational induction.

Anesthesia, General↗
PubMed2002

Do women have a hidden heat period?

This article aims to throw light on the controversial topic of whether women have a 'heat' period within their menstrual cycle. The majority of publications in this field report, in addition to a periovulatory peak, no changes at all or even rises in male- and female-initiated sexual activity, woman's sexual desire, autosexual activity and sexual arousability, and interpersonal sexual activities during the mid-follicular and late luteal phases. The lack of a distinct pattern of women's sexual behaviour across the menstrual cycle may be explained by the interplay between cyclical endocrine fluctuations and many psychological, social, cultural and environmental factors, as well as the methodological shortcomings associated with menstrual cycle research. However, studies focused on cycling changes in women's olfactory and visual perception show that, in comparison with women at other phases of the menstrual cycle, women at mid-cycle exhibit increased sexual motivation that biases recognition performance towards objects with a sexual meaning, evaluate the unattractive sweat substance androstenone as more pleasant, and display enhanced preference for the odour and face shape of masculinized, physically attractive and symmetric men. On the other hand, men find the scent of women at mid-cycle more pleasant and sexually attractive than during the luteal phase.

Cues↗
PubMed2006

The chemoreceptor superfamily in the honey bee, Apis mellifera: expansion of the odorant, but not gustatory, receptor family.

The honey bee genome sequence reveals a remarkable expansion of the insect odorant receptor (Or) family relative to the repertoires of the flies Drosophila melanogaster and Anopheles gambiae, which have 62 and 79 Ors respectively. A total of 170 Or genes were annotated in the bee, of which seven are pseudogenes. These constitute five bee-specific subfamilies in an insect Or family tree, one of which has expanded to a total of 157 genes encoding proteins with 15%-99% amino acid identity. Most of the Or genes are in tandem arrays, including one with 60 genes. This bee-specific expansion of the Or repertoire presumably underlies their remarkable olfactory abilities, including perception of several pheromone blends, kin recognition signals, and diverse floral odors. The number of Apis mellifera Ors is approximately equal to the number of glomeruli in the bee antennal lobe (160-170), consistent with a general one-receptor/one-neuron/one-glomerulus relationship. The bee genome encodes just 10 gustatory receptors (Grs) compared with the D. melanogaster and A. gambiae repertoires of 68 and 76 Grs, respectively. A lack of Gr gene family expansion primarily accounts for this difference. A nurturing hive environment and a mutualistic relationship with plants may explain the lack of Gr family expansion. The Or family is the most dramatic example of gene family expansion in the bee genome, and characterizing their caste- and sex-specific gene expression may provide clues to their specific roles in detection of pheromone, kin, and floral odors.

Animals↗
PubMed1990

[Olfaction in laryngectomized patients: effect of the phonatory prosthesis].

We have studied olfaction in 20 laryngectomies, only 10 of which were supplied with phonatory prosthesis. We conclude that patients without prosthesis show a higher threshold for perception of pure olfactory stimulants, whereas in those provided with the prosthesis the pure olfactory threshold remains within normal values.

Adult↗
PubMed1986

[Unusual hallucinatory forms of paranoid disorders in late schizophrenia].

The authors studied 62 patients with late schizophrenia with the predominance of elementary misperceptions. The main variants of such psychoses with auditory, olfactory and tactile perceptive disturbances have been identified. The authors also ascertained common typological signs distinguishing these psychoses from the classical paranoids of late age. A possible role of the age and environmental factors in the formation of the above psychoses is considered.

Age Factors↗
PubMed1984

Psychomotor and social development of breast-fed and bottle-fed babies during their first year of life.

Until about 30 years ago breast-feeding was the natural and common method of infant feeding. With increasing technical possibilities in food industry, transfer of birth into hospital and displacement of female activities outside the family, the frequency of breast-feeding decreased, being replaced by artificial feeding methods. This work treats the impact of the two feeding methods (breast and bottle feeding) on the psychomotor and social development of the baby in the first year of life. The theoretical part gives a review of the mother-child interaction and the psychomotor and social development. As hypotheses have been proposed the suppositions that breast-feeding in the first three months of life leads to essential developmental advances in psychomotor and, above all, social maturity. This is due to the intensive visual and olfactorial experience and perception, the advantages of nutrients in breast-milk and, last not least, to the infant's autonomy regarding food quantity and time intervals. The quality of mother-child interaction is essentially influenced by the feeding method, because distance and proximity have an essential influence on their relation. As an important sign of intellectual maturity was regarded to fear reaction to strangers. The empirical part examines the hypotheses by comparing the development of breast-fed and bottle-fed babies. The psychomotor and social development of breast-fed babies clearly differs from that of bottle-fed ones and leads at the age of 12 months to significant developmental advantages of the psychomotor and social capabilities. Some suggestions are given to ensure mental health in the first year of life.

Bottle Feeding↗