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Results for “Olfactory Perception”

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At least 649 records · Page 36Linked to original sources
PubMed2005

Ultrasonic songs of male mice.

Previously it was shown that male mice, when they encounter female mice or their pheromones, emit ultrasonic vocalizations with frequencies ranging over 30-110 kHz. Here, we show that these vocalizations have the characteristics of song, consisting of several different syllable types, whose temporal sequencing includes the utterance of repeated phrases. Individual males produce songs with characteristic syllabic and temporal structure. This study provides a quantitative initial description of male mouse songs, and opens the possibility of studying song production and perception in an established genetic model organism.

Animals↗
PubMedDate not supplied

Visual hallucinations.

Hallucinations may be defined as perceptions that occur in the absence of a corresponding stimulus. They can involve any of the five senses, hence visual, auditory, tactile, gustatory and olfactory hallucinations. By contrast, illusions depend upon a misinterpretation of an external stimulus. In this review we outline the causes, and describe the characteristics of various hallucinatory states. This should help in the assessment of a patient presenting with visual hallucinations.

Eye Diseases↗
PubMed1998

Multitasking in the olfactory system: context-dependent responses to odors reveal dual GABA-regulated coding mechanisms in single olfactory projection neurons.

Studies of olfaction have focused mainly on neural processing of information about the chemistry of odors, but olfactory stimuli have other properties that also affect central responses and thus influence behavior. In moths, continuous and intermittent stimulation with the same odor evokes two distinct flight behaviors, but the neural basis of this differential response is unknown. Here we show that certain projection neurons (PNs) in the primary olfactory center in the brain give context-dependent responses to a specific odor blend, and these responses are shaped in several ways by a bicuculline-sensitive GABA receptor. Pharmacological dissection of PN responses reveals that bicuculline blocks GABAA-type receptors/chloride channels in PNs, and that these receptors play a critical role in shaping the responses of these glomerular output neurons. The firing patterns of PNs are not odor-specific but are strongly modulated by the temporal pattern of the odor stimulus. Brief repetitive odor pulses evoke fast inhibitory potentials, followed by discrete bursts of action potentials that are phase-locked to the pulses. In contrast, the response to a single prolonged stimulus with the same odor is a series of slow oscillations underlying irregular firing. Bicuculline disrupts the timing of both types of responses, suggesting that GABAA-like receptors underlie both coding mechanisms. These results suggest that glomerular output neurons could use more than one coding scheme to represent a single olfactory stimulus. Moreover, these context-dependent odor responses encode information about both the chemical composition and the temporal pattern of the odor signal. Together with behavioral evidence, these findings suggest that context-dependent odor responses evoke different perceptions in the brain that provide the animal with important information about the spatiotemporal variations that occur in natural odor plumes.

Action Potentials↗
PubMed2006

Smell images and the flavour system in the human brain.

Flavour perception is one of the most complex of human behaviours. It involves almost all of the senses, particularly the sense of smell, which is involved through odour images generated in the olfactory pathway. In the human brain, the perceptual systems are closely linked to systems for learning, memory, emotion and language, so distributed neural mechanisms contribute to food preference and food cravings. Greater recognition of the role of the brain's flavour system and its connection with eating behaviour is needed for a deeper understanding of why people eat what they do, and to generate better recommendations about diet and nutrition.

Brain↗
PubMed2005

Interactions between acetoin, a plant volatile, and pheromone in Rhynchophorus palmarum: behavioral and olfactory neuron responses.

Aggregation of Rhynchophorus palmarum weevils on host plants is mediated by a male pheromone (rhynchophorol: R) and host-plant volatiles (PVs) acting in synergy. Synthetic PV blends synergizing pheromone contain acetoin (A) and ethyl acetate (EtAc). R, A, and EtAc are detected by specialized olfactory receptor neurons (ORNs). In addition, particular types of ORNs are tuned to both A and R. To specify the role played by acetoin in pheromone perception, we recorded the responses of ORNs to 100 ng of A or R presented either separately or mixed. Behavioral responses to R, A, and EtAc were studied in a four-armed olfactometer and by field trapping. We screened 59 R-, A-, and AR-tuned ORNs by recording specific responses to odors presented either separately or mixed. Stimulations by blends elicited complex response profiles from the three ORN types: some gave synergistic responses, others were inhibited, and the remainder responded as though both odors were detected independently. Several gave either a weak or no response to a first stimulation by R, but responded clearly to a second stimulation after an intercalary stimulation by A. In the olfactometer, both sexes were more attracted to a blend of A + R (1 + 0.01 ng/sec) than to pure compounds, whereas EtAc did not enhance response to R. Pheromone-baited traps (1 mg/day) containing PV blends (650 mg/day) based on an ethanol/EtAc blend (1:1), plus either 5 or 10% A, or a more complex reference blend, or sugarcane (natural pheromone synergist), caught similar numbers of weevils and about twice as many insects as a control ethanol/EtAc blend. Traps with only pheromone caught about 10 times fewer insects. Behavioral results support the role of acetoin as a pheromone synergist for R. palmarum, and electrophysiological data provide evidence of modulation of peripheral sensory responses to pheromone by acetoin. Sexual dimorphism was observed neither at the ORN nor at the behavioral levels.

Acetoin↗
PubMed1996

Morphogenesis of the brain in larval and juvenile Japanese eels, Anguilla japonica.

We compared the morphology, including relative volumes (RV), of some brain regions in leptocephalus larvae (10-30 mm in total length), glass eels (elvers), young, and immature pre-adults of the Japanese eel Anguilla japonica. The external brain shape of the leptocephali gradually changes from a laterally compressed one to a depressed elongated one. These changes are fundamentally due to biased growth of the telencephalon and optic tectum. The dramatic brain transformation progresses until the juvenile stage and culminates in an adult-type brain arrangement, with a developed cerebellum and eminentia granularis and a much more flattened appearance. The RVs of brain regions closely related to somatic sensory functions are quite different in larvae and juveniles. The larvae possess larger optic tecta and smaller chemo- and mechanosensory regions than the juveniles. The RV of the olfactory bulb increases, and that of the optic tectum decreases, until the adult stage, unlike the condition in a pelagic fish, Pagrus major, suggesting that adult eels are inferior to pelagic fishes in visual perception. In contrast, the brain morphology of the larvae suggests that they are equipped with a well-developed visual system, while the functional significance of the system still remains a mystery. It might be important for feeding, orientation and diurnal vertical migration of the larvae.

Anguilla↗
PubMed2003

Configurational and nonconfigurational interactions between odorants in binary mixtures.

Studies on odor mixture perception suggest that although odor components can often be identified in mixtures, mixtures can also give rise to novel perceptual qualities that are not present in the components. Using an olfactory habituation task, the authors evaluated how the perceptual similarity between components in a mixture affects the perceptual quality of the mixture itself. Rats perceived binary mixtures composed of similar components as different from their 2 components, whereas binary mixtures composed of dissimilar components were perceived as very similar to their components. Results show that for both types of mixtures, pretraining to Component A reduces subsequent learning about Component B in rats trained in the presence of A.

Animals↗
PubMed1997

Orientation responses to biological odours in the human newborn. Initial pattern and postnatal plasticity.

The initial pattern and development of odour preference was studied in infants simultaneously exposed to amniotic fluid (AF) and maternal lacteal secretion (L). Five groups of varying age (range: 1-5 days) and breast-feeding experience (range: 0-32 feeds) were studied. Before postnatal day 3, no evidence of differentiation of AF and L was apparent. After 3 days and 7-12 breast-feeding episodes, a significant preference for L arised. The initial stage (days 1-3) may reflect fetal acquisition of AF odour and sensory/motivational equivalence of AF and L odours. The second stage (days 4-5) may reflect the infants' perception of change in milk quality and increasing experience with milk. This sequential development attests to a high plasticity in the initial stage of human olfactory development.

Age Factors↗
PubMed1998

Odor structure-activity relationships of carboxylic acids correspond between squirrel monkeys and humans.

With use of a conditioning paradigm, the ability of four squirrel monkeys to distinguish n-valeric acid from n-forms and isoforms of other carboxylic acids (acetic acid to octanoic acid) was investigated. All four animals were clearly able to discriminate between all odor pairs tested and showed a significant negative correlation between discrimination performance and structural similarity of odorants in terms of differences in carbon chain length of the carboxylic acids. Branching of the carbon chain was also found to affect odorant quality because all animals performed better in discriminating n-valeric acid from isoforms of other carboxylic acids compared with the corresponding n-forms of these substances. With use of a triple forced-choice procedure, 10 human subjects were tested on the same tasks in parallel and showed a very similar pattern of discrimination performance compared with the squirrel monkeys. Thus the results of this study provide evidence of well-developed olfactory discrimination ability in squirrel monkeys for carboxylic acids and support the assumption that human and nonhuman primates may share common principles of odor quality perception.

Adult↗
PubMed1987

Pakicetus inachus and the origin of whales and dolphins (Mammalia: Cetacea).

The present paper is concerned with the comparative morphology of the archeocete and odontocete skull. Among the archeocetes, the recently described lower Eocene Pakicetus inachus obviously represents an early stage of adaptation to aquatic life. The morphology of the incomplete cranial remains, however, gives no evidence that Pakicetus was an amphibious intermediate stage. The evolution of advanced archeocetes and odontocetes is characterized by the successive acquirement of new morphological devices related to the emission and perception of ultrasound under water. The formation of a sonar system in odontocetes obviously not only helped to compensate for the loss of the peripheral olfactory system but moreover was a substantial factor in the evolution of the exceptional dolphin brain.

Animals↗
PubMed2003

Olfactory sensitivity for aliphatic esters in spider monkeys (Ateles geoffroyi).

Using a conditioning paradigm, the authors investigated the olfactory sensitivity of 3 spider monkeys (Ateles geoffroyi) for a homologous series of aliphatic esters (ethyl acetate to n-octyl acetate) and isomeric forms of some of these substances. With all odorants, the monkeys significantly discriminated concentrations below 1 ppm from the odorless solvent, and in several cases, individual monkeys even demonstrated thresholds below 1 ppb. The results showed spider monkeys to have a high olfactory sensitivity for aliphatic esters, which for the majority of substances matches or even is better than that of species such as the rat, the mouse, or the dog. These findings support the assumption that between-species comparisons of neuroanatomical features are poor predictors of olfactory performance.

Acetates↗
PubMed2006

RETRACTED: Combinatorial effects of odorant mixes in olfactory cortex.

In mammals, each odorant is detected by a combination of different odorant receptors. Signals from different types of receptors are segregated in the nose and the olfactory bulb, but appear to be combined in individual neurons in the olfactory cortex. Here, we report that binary odorant mixes stimulate cortical neurons that are not stimulated by their individual component odorants. We propose that cortical neurons require combinations of receptor inputs for activation and that merging the receptor codes of two odorants provides novel combinations of receptor inputs that stimulate neurons beyond those activated by the single odorants. These findings may explain why odorant mixtures can elicit novel odor percepts in humans.

Animals↗
PubMed1993

Depletion of olfactory bulb norepinephrine by 6-OHDA disrupts chemical cue but not social recognition responses in male rats.

In the present experiment, 6-OHDA was infused directly into the olfactory bulb (OB) to produce a localized neurotoxic lesion. Habituation/dishabituation behavioral tests were then conducted to measure recognition responses to chemical cues (urine as a stimulus) and to social stimuli (ovariectomized rat as a stimulus). Infusion of 6-OHDA resulted in a near complete depletion of OB-norepinephrine (NE), whereas it had little effect (15% reduction) on OB dopamine (DA) contents. Nor were any significant effects on hypothalamic, hippocampal, olfactory tubercle, and corpus striatal NE and DA contents observed. Behaviorally, dishabituation responses to chemical cues were greatly impaired, however, there was relatively little effect on social behavior dishabituation responses. These results demonstrate that 6-OHDA can be used to produce a near complete but localized depletion of OB-NE. This treatment impairs dishabituation responses to chemical cues but not social stimuli indicating that OB-NE appears necessary for processing of chemical cue, but not social memory recognition process.

Animals↗
PubMed2006

The nootropic and neuroprotective proline-containing dipeptide noopept restores spatial memory and increases immunoreactivity to amyloid in an Alzheimer's disease model.

The effects of the novel proline-containing nootropic and neuroprotective dipeptide, noopept (GVS-111, N-phenylacetyl-L-prolylglycine ethyl ester) were investigated in NMRI mice following olfactory bulbectomy. We have shown previously that these animals developed Alzheimer's disease (AD)-like behaviour, morphology and biochemistry including impairment of spatial memory, regional neuronal degeneration and elevated Abeta peptide brain levels. In the current investigation, spatial memory was assessed using the Morris water maze and serum antibodies to in vitro morphologically characterized amyloid structures of both Abeta((25-35)) peptide and equine lysozyme, as well as to neurotrophic glial factor S100b, were analyzed by enzyme-linked immunosorbent assay (ELISA). Noopept (administered at a dose of 0.01 mg/kg for a period of 21 days and during a further 5 days training) restored spatial memory and increased serum antibody levels to oligomers of Abeta((25-35)) peptide but not to equine lysozyme amyloid or S100b protein in bulbectomized animals. The positive immunotropic effect of noopept to Abeta((25-35)) peptide prefibrillar aggregates was more marked in sham-operated compared to the bulbectomized subjects which were characterized by an overall suppression of immunoreactivity. Enhancement of the immune response to Abeta((25-35)) peptide prefibrils caused by noopept may attenuate the neurotoxic consequences of amyloid fibrillization and also be associated with an improvement in spatial memory in bulbectomized mice. These actions of noopept, combined with its previously reported neuroprotective and cholinomimetic properties, suggests that this dipeptide may well be useful for improving cognitive deficits induced by neurodegenerative diseases.

Alzheimer Disease↗
PubMed2005

Smell perception during early pregnancy: no evidence of an adaptive mechanism.

OBJECTIVE: It has been suggested that nausea and vomiting in pregnancy is an evolutionary adaptive mechanism to avoid the ingestion of potentially harmful foods. It has also been suggested that the mechanism that triggers nausea and vomiting in pregnancy may be olfaction and that olfactory senses are invoked to provide this protection. This study aimed to test this theory in a systematic design. DESIGN: Cross sectional study. SETTING: The antenatal department of a maternity hospital in the north of England. SAMPLE: Three groups of participants: pregnant women (n= 55), non-pregnant women (n= 42) and men (n= 48). METHODS: Sensitivity was tested towards the odours of six standard stimuli (half safe and half associated with potentially harmful compounds). MAIN OUTCOME MEASURES: Odour rating of likeness, strength and pleasantness. RESULTS: Pregnant women rated safe and odours with potentially harmful compounds differently but not more so than men or non-pregnant women. There was no evidence that pregnancy changed the olfactory processes from the non-pregnant state and only slight differences between pregnant women and men were recorded. CONCLUSIONS: There was no evidence that olfactory processes had undergone any adaptation during pregnancy. The ability to differentiate safe from potentially harmful compounds was common to all three groups studied.

Adaptation, Physiological↗