PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Olfactory Perception”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed2006

Strong single-fiber sensory inputs to olfactory cortex: implications for olfactory coding.

Olfactory information is first encoded in a combinatorial fashion by olfactory bulb glomeruli, which individually represent distinct chemical features of odors. This information is then transmitted to piriform (olfactory) cortex, via axons of olfactory bulb mitral and tufted (M/T) cells, where it is presumed to form the odor percept. However, mechanisms governing the integration of sensory information in mammalian olfactory cortex are unclear. Here we show that single M/T cells can make powerful connections with cortical pyramidal cells, and coincident input from few M/T cells is sufficient to elicit spike output. These findings suggest that odor coding is broad and distributed in olfactory cortex.

Action Potentials↗
PubMed1985

Drosophila mushroom body mutants are deficient in olfactory learning.

Two Drosophila mutants are described in which the connections between the input to and the output from the mushroom bodies is largely interrupted. In all forms of the flies (larva, imago, male, female) showing the structural defect, olfactory conditioning is impaired. Learning is completely abolished when electroshock is used as reinforcement and partially suppressed in reward learning with sucrose. No influence of the mushroom body defect on the perception of the conditioning stimuli or on spontaneous olfactory behavior is observed. The defect seems not to impair learning of color discrimination tasks or operant learning involving visual cues.

Animals↗
PubMedDate not supplied

Configurational and elemental odor mixture perception can arise from local inhibition.

Contrast enhancement via lateral inhibitory circuits is a common mechanism in sensory systems. We here employ a computational model to show that, in addition to shaping experimentally observed molecular receptive fields in the olfactory bulb, functionally lateral inhibitory circuits can also mediate the elemental and configurational properties of odor mixture perception. To the extent that odor perception can be predicted by slow-timescale neural activation patterns in the olfactory bulb, and to the extent that interglomerular inhibitory projections map onto a space of odorant similarity, the model shows that these inhibitory processes in the olfactory bulb suffice to generate the behaviorally observed inverse relationship between two odorants' perceptual similarities and the perceptual similarities between either of these same odorants and their binary mixture.

Action Potentials↗
PubMed2001

[Neuronal connectivity and chemical mediators involved in olfactory message transmission].

In this review, we discuss some of the neural processes involved in the perception of odors which, together with audition and vision, provide essential information for analyzing our surroundings. We shall see how odor detection and learning induce substantial structural and functional changes at the first relay of the olfactory system, i.e., the main olfactory bulb. Among the mechanisms which participate in these modifications are changes in the cell's responses to a transmitter and the persistence of a high level of interneuron neurogenesis within the adult olfactory bulb. Our goal is to present some observations related to these two phenomena that may aid in understanding the neural mechanisms of sensory perception and shed light on the cellular basis of olfactory learning. To this purpose, we summarize the current ideas concerning the molecular mechanisms and organizational strategies used by the olfactory system to transduce, encode, and process information at various levels in the olfactory sensory pathway. Due to space constraints, this review focuses exclusively on the olfactory systems of vertebrates and primarily those of mammals.

Electrophysiology↗
PubMed2001

New GPCRs from a human lingual cDNA library.

Sweet and bitter taste perception involve G protein coupled receptors (GPCRs) present at the taste receptor cell surface. It is likely that various mechanisms are active and various families of GPCRs are involved in the perception of these tastes. The expression of GPCRs in human tongue was studied using degenerated primers corresponding to transmembrane domains 2 or 3 (for 5' primer), 6 or 7 (for 3' primer) of olfactory-like receptors in reverse transcription-polymerase chain reaction experiments. It was demonstrated that four previously identified, eight new olfactory-like receptor genes, three previously known and eight new olfactory-like receptor pseudogenes, mostly located on chromosome 11, are expressed in adult tongue and/or in fetal tongue. Previously identified genes include HGMP071, HTPCR06, TPCR120 and TPCR85 whose cDNAs were originally isolated from male germinal cells. New genes were named JCG1, JCG2, JCG3, JCG4, JCG5, JCG6, JCG9 and JCG10. HGMP071, HTPCR06, TPCR120, JCG3 and JCG5 are also expressed in the epithelium of adult tongue, whereas all these genes are expressed in fetal tongue. Although functional studies are needed before definitive conclusions are made, the obtained results imply that lingual olfactory-like receptors could be involved in taste perception.

Amino Acid Sequence↗
PubMed1999

Optical imaging of odor-evoked glomerular activity patterns in the antennal lobes of the ant camponotus rufipes

Ants have a well developed olfactory sense, which they need both for the perception of environmental chemicals, and for a highly sophisticated intraspecific communication system based on pheromones. The question arises therefore as to how different odors are coded in the antennal lobe, the first central neuropil to process olfactory information. We measured odor-evoked activity patterns using in vivo neuropil calcium recording in the antennal lobe of the ant Camponotus rufipes. We found that (a) odors elicit focal activity spots (diameter ca. 20 &mgr;m) which most probably represent the olfactory glomeruli; (b) different odors are coded in odor specific patterns of such activated spots, and a particular spot can participate in the pattern for different odors; (c) calcium increased in the activated spots within the 2-s stimulation period and slowly declined thereafter.

Journal Article↗
PubMedDate not supplied

[Spatial perception of stimuli during unilateral exclusion of the temporal portion of the neocortex by cold].

Behavioral reaction of twelve cats were studied in conditions of inactivation by cold of the temporal area (AI, AII, Ep and partly I-T) of one hemisphere. A typical vestibular ataxy was observed: deflection of the cats when walking, circular movements in the direction of the inactivated temporal area. Orienting reactions both to acoustic and photic stimuli persisted, but their spatial localization was completely lost. In every case the animals exhibited a clear orienting reaction towards the inactivated hemisphere, regardless of the localization of the source of signal. Reactions ot pain and olfactory stimulations likewise proceded in one direction. such a one-sided perception of sounds in the case of inactivation by cold of the temporal neocortex of one hemispheres is apparently due to the functional elimination of contralateral auditory structures. Disturbance of adequate spatial perception of photic, pain and olfactory stimuli under similar conditions results from a sharp drop in the tone predominantly of the ipsilateral hemisphere.

Animals↗
PubMed2004

Phenol and lactone receptors in the distal sensilla of the Haller's organ in Ixodes ricinus ticks and their possible role in host perception.

Extract of steer wool odor was found to excite olfactory receptor(s) in a wall-pore olfactory sensillum on the distal knoll of the Haller's organ. Three active volatile compounds were revealed in this odor by gas chromatography. Electrophysiological experiments revealed two types of receptors (sensory neurons) within the sensilla examined. One type of receptor responded only to phenolic derivatives, such as o-chlorophenol, o-bromophenol, o-methylphenol, 2,6-dichlorophenol, 2,6-dibromophenol, 2,4,6-trichlorophenol, but not to o-nithrophenol, p-methylphenol, 2,5-dichlorophenol, 3,5-dichlorophenol, 2,6-dinithrophenol, 2,6-dimethylphenol, and pentachlorophenol. The other type of receptor responded only to gamma-valerolactone. It is assumed that these cells play an important role in perception of a host from long distances (10-15 m), which is typical of Ixodes ricinus ticks.

Animals↗
PubMed2000

Sniffin'Sticks: a new olfactory test battery.

The olfactory test battery "Sniffin'Sticks" comprises a perception threshold test, an odour discrimination test and an odour identification test. The purpose of this study was to examine the suitability of the Sniffin'Sticks for use in everyday practice and to obtain (at least provisional) normal values. Thirty normosmic and 15 anosmic volunteers were examined with the Sniffin'Sticks and the "University of Pennsylvania Smell Identification Test" (UPSIT). All three Sniffin'Sticks tests distinguish between normosmics and anosmics in a highly significant manner. The good correlation of the individual tests with each other and with the results of the UPSIT documents the reliability of the test results. Critical mention must be made of the overly complex determination of the olfactory threshold. In conclusion, the Sniffin'Sticks test battery provides a validated instrument adapted to European conditions for the examination of olfactory disorders. It has proven successful in everyday clinical practice and constitutes a major aid for compiling medical certificates.

Humans↗
PubMedDate not supplied

Local neurons play key roles in the mammalian olfactory bulb.

Over the past few decades, research exploring how the brain perceives, discriminates, and recognizes odorant molecules has received a growing interest. Today, olfaction is no longer considered a matter of poetry. Chemical senses entered the biological era when an increasing number of scientists started to elucidate the early stages of the olfactory pathway. A combination of genetic, biochemical, cellular, electrophysiological and behavioral methods has provided a picture of how odor information is processed in the olfactory system as it moves from the periphery to higher areas of the brain. Our group is exploring the physiology of the main olfactory bulb, the first processing relay in the mammalian brain. From different electrophysiological approaches, we are attempting to understand the cellular rules that contribute to the synaptic transmission and plasticity at this central relay. How olfactory sensory inputs, originating from the olfactory epithelium located in the nasal cavity, are encoded in the main olfactory bulb remains a crucial question for understanding odor processing. More importantly, the persistence of a high level of neurogenesis continuously supplying the adult olfactory bulb with newborn local neurons provides an attractive model to investigate how basic olfactory functions are maintained when a large proportion of local neurons are continuously renewed. For this purpose, we summarize the current ideas concerning the molecular mechanisms and organizational strategies used by the olfactory system to encode and process information in the main olfactory bulb. We discuss the degree of sensitivity of the bulbar neuronal network activity to the persistence of this high level of neurogenesis that is modulated by sensory experience. Finally, it is worth mentioning that analyzing the molecular mechanisms and organizational strategies used by the olfactory system to transduce, encode, and process odorant information in the olfactory bulb should aid in understanding the general neural mechanisms involved in both sensory perception and memory. Due to space constraints, this review focuses exclusively on the olfactory systems of vertebrates and primarily those of mammals.

Animals↗
PubMed1983

Release of LH in the female rat by olfactory stimuli. Effect of the removal of the vomeronasal organs or lesioning of the accessory olfactory bulbs.

The release of LH in ovariectomized, estrogen-primed rats exposed to male or female rats was studied. The concentration of LH in the serum was measured in blood samples obtained by an indwelling jugular cannula. A blood sample was taken at 12.00 h and then every hour up to 18.00 h following exposure to another rat on the opposite side of a double wire mesh screen. LH in the serum of control non-exposed rats showed a small rise between 16.00 and 18.00 h as compared to earlier values. Rats exposed to intact or castrated male rats exhibited an enhanced release. Exposure to ovariectomized rats failed to induce any change in the release of LH but exposure to ovariectomized, estrogen-primed rats produced a significant increase. No effect on LH release was seen in animals exposed to a female diestrous rat or to a pregnant rat. Rats exposed to an empty cage which had been soiled by housing a male rat for 3 days, showed an enhanced release of LH similar to those exposed to a cage containing the male rat, indicating the importance of olfactory stimuli in the response. Ovariectomized rats whose vomeronasal organs had been removed or whose accessory olfactory bulbs were lesioned, failed to show any effect on the release of LH when exposed to a male rat. It is concluded that olfactory stimuli arising from male or female rats are capable of modulating the release of LH in female rats and that perception of these stimuli involves the vomeronasal organ-accessory olfactory bulb system.

Animals↗
PubMed2007

Phenylthiocarbamide (PTC) perception in patients with schizophrenia and first-degree family members: relationship to clinical symptomatology and psychophysical olfactory performance.

The inability to taste phenylthiocarbamide (PTC; "taste-blindness") has been associated with a number of medical and neurological illnesses not typically related to taste. We examined PTC sensitivity in 67 schizophrenia patients, 30 healthy controls, and 30 first-degree relatives to determine whether taster status could represent a simple vulnerability marker. A higher prevalence of non-tasters was seen in patients and family members relative to healthy controls. Among patients, non-tasters exhibited increased levels of negative and first-rank symptoms as well as poorer right nostril odor identification skills relative to PTC tasters. These differences were not explained by age, sex, education, smoking, or intensity differences. Phenotypic variation in PTC sensitivity is thought to be genetic in origin and suggests greater illness risk for those subjects with recessive taster alleles.

Adult↗
PubMedDate not supplied

Reduced olfactory performance in patients with major depression.

The aim of the present study is to investigate olfactory sensitivity and odor evaluations in a homogeneous sample of unipolar depressive patients using pure olfactory odors. Twenty-four in-patients with major depressive disorder (MDD) were investigated during their acute depressive phase. Eighteen of them participated a second time after successful treatment. A group of healthy subjects, matched by age, sex, and smoking behavior, served as a control. Olfactory sensitivity, as measured by threshold tests, was strongly reduced in patients with severe depression. Additional correlative analyses revealed that the lowered sensitivity could partly be predicted by high depression scores. After successful medical treatment, these sensitivity differences were reduced and did not reach the significance level. The subjective odor evaluations (valence and intensity ratings) were not markedly changed in general. The results reveal that olfactory performance in MDD patients is reduced at an early perceptional level of stimulus processing. It is discussed whether this effect can be attributed to the close functional connection between the main olfactory bulb and the amygdala.

Adult↗
PubMed1998

Presence of cues from stressed conspecifics increases reactivity to aversive events in cattle: evidence for the existence of alarm substances in urine.

In gregarious species like cattle, the presence of partners often affects fear-related reactions. The first experiment investigated whether behavioral and physiological responses to stress depend on the emotional state of the partner. Aubrac heifers were presented with food in a novel environment. Compared to heifers in the presence of a companion that had been previously habituated to the environment without receiving shocks, those in the presence of a companion animal that had previously received electric shocks in that environment had a stronger increase of cortisol response (11.2+/-1.1 vs. 7.4+/-0.9 ng/mL), showed a significantly longer latency to feed (60.1+/-12.3 vs. 17.8+/-5.9 s), and fed more slowly (54.5+/-11.4 vs. 110+/-7.3 s). After repeated exposure to the test conditions, when heifers of both treatments fed rapidly after entrance, response to an unexpected air blast from the feeding bucket was measured. Heifers in the presence of a stressed companion showed an increased latency to feed again compared to those with a nonstressed companion (44.5+/-5.1 vs. 22.8+/-4.3 s). Stressed companions urinated during tests; therefore the second experiment investigated whether heifers respond differently to urine collected from stressed and nonstressed conspecifics. In a first test, heifers were presented with food on a grid in a bucket in a novel environment. They had a longer latency to feed when the bucket contained urine from stressed rather than from nonstressed conspecifics underneath the grid (128.1+/-9.6 vs. 108.2+/-4.9 s). In a second test, heifers were presented with a novel object in a familiar environment. Heifers showed a longer latency to explore the object when it had been sprayed with urine from stressed compared to urine from nonstressed conspecifics (215.2+/-45.0 vs. 25.8+/-8.6 s). The results show that heifers perceive the state of increased stress of conspecifics and become more fearful as a result. They further show that this perception is at least partly mediated by olfactory cues in the urine.

Animals↗
PubMed2000

Olfactory functions are mediated by parallel and hierarchical processing.

How the human brain processes the perception, discrimination, and recognition of odors has not been systematically explored. Cerebral activations were therefore studied with PET during five different olfactory tasks: monorhinal smelling of odorless air (AS), single odors (OS), discrimination of odor intensity (OD-i), discrimination of odor quality (OD-q), and odor recognition memory (OM). OS activated amygdala-piriform, orbitofrontal, insular, and cingulate cortices and right thalamus. OD-i and OD-q both engaged left insula and right cerebellum. OD-q also involved other areas, including right caudate and subiculum. OM did not activate the insula, but instead, the piriform cortex. With the exception of caudate and subiculum, it shared the remaining activations with the OD-q, and engaged, in addition, the temporal and parietal cortices. These findings indicate that olfactory functions are organized in a parallel and hierarchical manner.

Adult↗
PubMed2004

The nociceptin pharmacophore site for opioid receptor binding derived from the NMR structure and bioactivity relationships.

Nociceptin, a 17 amino acid opioid-like peptide that has an inhibitory effect on synaptic transmission in the nervous system, is involved in learning, memory, attention, and emotion and is also implicated in the perception of pain and visual, auditory, and olfactory functions. In this study, we investigated the NMR solution structure of nociceptin in membrane-like environments (trifluoroethanol and SDS micelles) and found it to have a relatively stable helix conformation from residues 4-17 with functionally important N-terminal residues being folded aperidoically on top of the helix. In functional assays for receptor binding and calcium flux, alanine-scanning variants of nociceptin indicated that functionally important residues generally followed helix periodicity, consistent with the NMR structural model. Structure-activity relationships allowed identification of pharmacophore sites that were used in small molecule data base searches, affording hits with demonstrated nociceptin receptor binding affinities.

Alanine↗
PubMed1999

Do chemosensory changes influence food intake in the elderly?

Food intake declines with age, and elderly individuals frequently report a decrease in appetite. Changes in chemosensory systems may partially explain this low intake. However, few data have directly linked changes in gustatory or olfactory function to food choice or intake. In two studies, taste perception and preference were unrelated to sodium chloride or sugar intakes. Olfaction may be more affected by age than taste. Olfactory dysfunction is associated with decreased enjoyment of food, and adding odors to foods can increase intake in some elderly individuals. The consumption of a varied diet depends in part on sensory-specific satiety (a decrease in the pleasantness of a food as it is consumed). Sensory-specific satiety diminishes with age, and this could be part of the explanation of why some elderly individuals have little variety in their diets. However, the impact of chemosensory deficits on nutritional status depends on a number of social and environmental factors. For example, despite their age, financially secure, free-living healthy older men and women consumed more varied diets than young adults. Changes in mechanisms regulating food intake can make it difficult for some elderly individuals to maintain energy balance. When chemosensory impairments are combined with changes in food intake regulatory mechanisms, the risk for nutritional deficiencies may be high. If we are to optimize food intake and nutritional status in the elderly, additional basic studies on how changes in chemosensory systems associated with aging affect food selection and intake are required.

Aged↗