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Results for “Olfactory Perception”

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PubMed1985

Odor signatures and kin recognition.

The basis of olfactory signatures mediating human kin recognition was investigated in two experiments. The odors of mothers and offspring were correctly matched (by subjects unfamiliar with the stimulus individuals) at a greater than chance frequency. In contrast, subjects were not able reliably to match the odors of husbands and wives. These data support the hypotheses that characteristic individuals odors are genetically mediated and that kin recognition should be facilitated by the similarity of such familiar odors among close relatives.

Adolescent↗

PubMed2003

Odor similarity does not influence the time needed for odor processing.

The brain's link between perception and action involves several steps, which include stimulus transduction, neuronal coding of the stimulus, comparison to a memory template and choice of an appropriate behavioral response. All of these need time, and many studies report that the time needed to compare two stimuli correlates inversely with the perceived distance between them. We developed a behavioral assay in which we tested the time that a honeybee needs to discriminate between odors consisting of mixtures of two components, and included both very similar and very different stimuli spanning four log-concentration ranges. Bees learned to discriminate all odors, including very similar odors and the same odor at different concentrations. Even though discriminating two very similar odors appears to be a more difficult task than discriminating two very distinct substances, we found that the time needed to make a choice for or against an odor was independent of odor similarity. Our data suggest that, irrespective of the nature of the olfactory code, the bee olfactory system evaluates odor quality after a constant interval. This may ensure that odors are only assessed after the olfactory network has optimized its representation.

Acyclic Monoterpenes↗

PubMed1998

5-HT4 receptors: gene, transduction and effects on olfactory memory.

In this paper we discuss 1) the primary structures, pharmacology, and brain distribution of cloned 5-HT4 receptors; 2) the chromosomal localization of the h5-HT4 receptor; 3) whether benzamides are full or partial agonists because of a species or a coupling difference; 4) the intrinsic activity of 5-HT4 receptors and inverse agonism of GR125487 in COS-7 cells but not in colliculi neurons; 5) the modulation of 5-HT4 receptor binding and activity; and 6) the long-term blockade of K+ channels by 5-HT4 agonists and its effect on olfactory memory. We conclude that 1) the cloning of 5-HT4 receptors in different species using RT-PCR from different tissues reveals the presence of several splice variants for 5-HT4 receptors differing in the C-terminal part, downstream from the amino acid L358; 2) the pharmacological properties of 5-HT4 receptors are dependent on the cellular context in which they are expressed; and 3) 5-HT4 agonists can be added to the list of compounds having pro-cognitive properties.

Alternative Splicing↗

PubMed1994

Odor plumes and how blue crabs use them in finding prey.

Orientation of animals using chemical cues often takes place in flows, where the stimulus properties of odorants are affected by the characteristics of fluid motion. Kinematic analysis of movement patterns by animals responding to odor plumes has been used to provide insight into the behavioral and physiological aspects of olfactory-mediated orientation, particularly in terrestrial insects. We have used this approach in analyzing predatory searching by blue crabs in response to plumes of attractant metabolites released from the siphons of live clams in controlled hydrodynamic environments. Crabs proceed directly upstream towards clams in smooth-turbulent flows and show high locomotory velocities and few periods of motionlessness. Crabs assume more indirect trajectories and display slower locomotion and more stopping in rough-turbulent flows. This degradation of foraging performance is most pronounced as flow shifts from a smooth- to a rough-turbulent regime, where the change in hydraulic properties is associated with contraction of the viscous sublayer region of the boundary layer. Because flow in this region is quasilaminar, the viscous sublayer may be a particularly effective vehicle for chemical stimulus transmission, such that orientation is severely compromised when it is reduced or removed. Our results also suggest that rheotactic and chemical information are both necessary for successful orientation. Perception of chemical cues acts to bias locomotion upcurrent, and feedback from odorant stimulus distributions appears directly to regulate subsequent stopping and turning en route to prey. Although the mechanisms of orientation to odorant plumes displayed by insects and blue crabs are largely similar, blue crabs appear to rely more heavily on spatial and/or temporal aspects of chemical stimulus distributions than has been suggested for insect systems.

Animals↗

PubMed2005

Home bases formed to visual cues but not to self-movement (dead reckoning) cues in exploring hippocampectomized rats.

Spatial theory proposes that the hippocampus contributes to exploratory behavior allowing animals to acquire information about their environment. In the present study, the exploratory movements of control rats, bulbectomized (anosmic) rats and hippocampectomized rats using the neurotoxin N-methyl-D-aspartate (NMDA) were monitored on a large circular table without walls and around which visual cues were manipulated. The rats displayed organized spatial behavior in that they developed home bases, one or more places operationally defined as those in which they spent a preponderance of time, in which they moved slowly, and to which they returned after excursions. Control rats and hippocampectomized rats were similar in that they established home bases: (i) adjacent to a proximal stable or moving visual landmark; (ii) in relation to more distant visual room cues; and (iii) in relation to contextually conditioned visual cues. Nevertheless, in exploratory tests given under infrared light, a wavelength to which rats are insensitive, control rats and bulbectomized rats established one or more home bases that were not dependent upon surface (e.g. olfactory) cues, whereas home base behavior was absent/fragmented in hippocampectomized rats. Thus, exploratory behavior, as exemplified by home base behavior, is organized in control and hippocampectomized rats in relation to visual cues, but is not organized in hippocampectomized rats when visual cues are absent. This result is discussed in relation to the idea that the hippocampus contributes to spatial behavior that is dependent upon guidance (dead reckoning) derived from self-movement cues.

Analysis of Variance↗

PubMed1997

Genome size, secondary simplification, and the evolution of the brain in salamanders.

Compared to other vertebrates, even including lampreys and hagfishes in some respects, salamanders exhibit a relatively simple organization of brain and sense organs which is illustrated here using the visual system as an example. The greatest simplicity is found in the bolitoglossine salamanders, yet all bolitoglossines possess highly projectile tongues and rely on vision for survival; furthermore, some species are agile and acrobatic. The unusual features of the visual system of salamanders include small numbers of large neurons, a low degree of morphological differentiation among neurons, a small proportion of myelinated axons in the optic nerve, and an optic tectum consisting essentially of a periventricular cellular layer and a superficial fiber layer. Similar features are found throughout the central nervous system of salamanders and in the lateral line, auditory and olfactory systems as well. Phylogenetic analysis shows that the most parsimonious interpretation of these data is that the simple organization of the brain and sense organs of salamanders was derived secondarily from a more complex ancestral state. We hypothesize that increased genome size has led to simplification of the nervous system in salamanders. Increased genome size appears to have had profound effects on neural development in salamanders, leading to paedomorphosis, the retention of juvenile or even embryonic characteristics into adulthood. In particular, large genome size is associated with large cell size and reduced rates of cell proliferation, migration and differentiation. Secondary simplification has constrained the function of the salamanders' visual system, primarily by increasing cell size and decreasing cell numbers. However, it also has provided an opportunity for the evolution of compensating mechanisms, which have helped to restore or even enhance visual function. Most apparent among the compensatory mechanisms of bolitoglossine salamanders is the presence of well developed ipsilateral retinotectal projections, which apparently enhance depth perception. It is difficult to explain the unusual history of the nervous system in salamanders solely in terms of natural selection and adaptation. Increasing genome size through selfish replication appears to have played a major role in the evolution of salamander brains by imposing functional constraints as well as creating opportunities for overcoming them.

Animals↗

PubMed2003

Effects of peak concentrations on the neurotoxicity of styrene in volunteers.

The manufacture of fibreglass reinforced plastic products may give rise to substantial peak exposures to styrene. Such exposure patterns need further consideration in terms of styrene neurotoxicity. The aim of this study was to evaluate the neurotoxic effects of short-term peak exposures in volunteers, at levels respecting the Quebec occupational exposure limits (8 hours time weighed average of 213 mg/m3 and 15 min average of 426 mg/ m3). The volunteers had not been previously exposed to styrene and they had no documented exposure to known neurotoxicants during the study. Twenty-four volunteers were exposed to five exposure scenarios during 6 hours: a, stable exposure to 106 mg/m3; b, variable exposure with a mean concentration of 106 mg/m3 with four 15 min peaks mounting up to 213 mg/m3; c, stable exposure to 213 mg/m3; d, variable exposure with a mean concentration of 213 mg/m3 and four peaks of 426 mg/m3 and e, two stable exposures to 5 mg/m3 (control). Before and after each exposure scenario, volunteers were submitted to a battery of sensory tests (visual and olfactory), neuropsychological tests (reaction time, attention, memory, psychomotor function), and self-evaluation questionnaires (mood and symptoms) in a test-retest design. The results show that the different exposure scenarios involving peak exposures did not influence either the performance to any test or subjective signs and symptoms. However, due caution must be exercised in extrapolation of the current results to occupational exposure since only acute exposures were tested and volunteers were at rest during exposure, which resulted in lower doses than those experienced by physically active workers.

Administration, Inhalation↗

PubMed1991

Temporal and hippocampal metabolic rate during an olfactory memory task assessed by positron emission tomography in patients with dementia of the Alzheimer type and controls. Preliminary studies.

Positron emission tomography with fludeoxyglucose F 18 was used to assess cortical metabolic rate during an olfactory memory task in six patients with dementia of the Alzheimer type. Metabolic activity was compared with that of both age-matched controls performing the olfactory task and controls resting with their eyes closed. Patients had lower metabolic rates in the anterior portion of the medial-temporal cortex than did controls, and the difference was greatest between patients and the controls performing the memory task. This region is known to receive a large olfactory input and has been implicated in the encoding of human memory. Normal controls resting with their eyes closed had significantly lower metabolic rates in this area when compared with normal controls performing the task. Our results are consistent with those of earlier reports of temporal lobe decreases in metabolic rate and extend them through the examination of areas salient to the behavioral loss.

Aged↗

PubMed2001

Sensory experience and sensory activity regulate chemosensory receptor gene expression in Caenorhabditis elegans.

Changes in the environment cause both short-term and long-term changes in an animal's behavior. Here we show that specific sensory experiences cause changes in chemosensory receptor gene expression that may alter sensory perception in the nematode Caenorhabditis elegans. Three predicted chemosensory receptor genes expressed in the ASI chemosensory neurons, srd-1, str-2, and str-3, are repressed by exposure to the dauer pheromone, a signal of crowding. Repression occurs at pheromone concentrations below those that induce formation of the alternative dauer larva stage, suggesting that exposure to pheromones can alter the chemosensory behaviors of non-dauer animals. In addition, ASI expression of srd-1, but not str-2 and str-3, is induced by sensory activity of the ASI neurons. Expression of two receptor genes is regulated by developmental entry into the dauer larva stage. srd-1 expression in ASI neurons is repressed in dauer larvae. str-2 expression in dauer animals is induced in the ASI neurons, but repressed in the AWC neurons. The ASI and AWC neurons remodel in the dauer stage, and these results suggest that their sensory specificity changes as well. We suggest that experience-dependent changes in chemosensory receptor gene expression may modify olfactory behaviors.

Animals↗

PubMed2005

Route finding by rats in an open arena.

Rats were repeatedly exposed to an open arena containing two depletable food sources in a discrete-trials procedure. Their movement patterns were recorded and compared to adaptive foraging tactics such as minimizing distance or energy expenditure, thigmotaxis, and trail following. They were also compared to the predictions of the associative route-finder model of Reid and Staddon [Reid, A.K., Staddon, J.E.R., 1998. A dynamic route finder for the cognitive map. Psychol. Rev. 105 (3), 585-601]. We manipulated the presence/absence of food, goal cups, and a wooden runway to determine the influence of local and distal stimuli (visual, olfactory, and tactile) on movement patterns. Increased experience in the arena produced decreases in travel distance and time to the food sources. Local and distal stimuli influenced movement patterns in ways compatible with visual beacons and trail following. The route-finder model accurately predicted movement patterns except those that were influenced by local and distal stimuli. These results show how certain stimuli influence movement and provide a guide for the incorporation of local and distal stimuli in a future version of the dynamic route-finder model.

Animals↗

PubMed2000

Learning to cope with two different food distributions: the performance of house mice (Mus musculus domesticus).

Search abilities of mice (Mus musculus domesticus) were evaluated using an arena closed by a ceiling in which 9 food sources (which mice could reach standing on their hind legs) could be arranged according to 2 configurations: a 3 x 3 square matrix and 3 clusters each containing 3 food sources. Testing conditions prevented olfactory and visual cues from being left after visits to food sources, and mice were able to choose alternative routes between food sources. Results showed that mice were more efficient with the matrix than with the cluster configuration. Sex differences were observed: Females improved their performance with both configurations, whereas males improved only with the matrix one. Mice did not develop evident search strategies that would minimize task complexity. Comparison with data published on capuchin monkeys revealed differences, with monkeys performing better with the cluster configuration than with the matrix and applying searching strategies.

Animals↗

PubMed1975

Olfactory discrimination, reversal learning, and stimulus control in rats.

Rats were trained to discriminate lights, tones, or odors and then given a series of discrimination reversals. Only rats trained with odors showed positive transfer on the first reversal and acquisition of a reversal set. Other experiments demonstrated that rats preferentially attend to odors when presented in compound with lights or tones; that odors exert more discriminative control than tones in tests using compound stimuli of competing sign; and that after pretraining on the positive stimulus, acquisition of an odor but not a light discrimination occurs with virtually no errors. These results demonstrate the importance of stimulus modality in the establishment of stimulus control and the need for more careful analysis of stimulus factors in cross-species comparisons of learning ability.

Animals↗

PubMed2004

Play deprivation without social isolation: housing controls.

Three experiments were conducted to control for the effects of housing conditions during play deprivation on subsequent play rebound in periadolescent rats. To address play deprivation without the confound of social isolation, in Experiment 1, pairs of subjects were housed either in cages divided by wire mesh that allowed for olfactory, visual, auditory, and tactile interactions with a same-sex age-mate but prevented rough and tumble play or in standard cages. Running wheels were provided to similarly housed subjects in Experiment 2 to control for the ability to engage in physical activity. In Experiment 3, standard and brooder cages were used to control for the effects of housing area. Play-deprived subjects in all conditions showed a greatly increased number of play responses immediately following deprivation. The results from these experiments more clearly indicate that the absence of play is the crucial feature that brings about play rebound following deprivation.

Age Factors↗

PubMed1990

Behavioral effects of early postnatal lead exposure in herring gull (Larus argentatus) chicks.

Lead exposure early in life affects behavioral and intellectual development in humans. In this paper, I use the herring gull, Larus argentatus, as an animal model to examine effects of lead exposure on early development. Like humans, birds rely mainly on visual and vocal, rather than olfactory, modes of communication. Each of 24 one-day-old herring gull chicks was randomly assigned to one of three treatment groups to receive a lead nitrate solution at a concentration of 0.0, 0.1 and 0.2 mg/g. The control dose was an equal volume of sterile saline. The trios were not siblings, but were matched by weight. Behavioral tests were performed either daily, every two to five days, or at the end of the experiment (45 days posthatching), depending on the nature of the experiment. The behavioral tests examined locomotion, balance, righting response, begging, recognition, thermoregulation and visual cliff. Although on most days, begging behavior, balance and righting response did not differ significantly, over the 45 days of the experiment control birds performed better on more days than the lead-injected birds. Balance was disturbed by lead-injection for the first six days following injection. Individual recognition developed by day 5 in control birds, by day 10 for 0.1 Pb mg/g birds, and by day 14 for 0.2 Pb mg/g birds. Depth perception and thermoregulation behavior were also adversely affected by lead.

Animals↗

PubMed2003

The subjective and reinforcing effects of visual and olfactory stimuli in alcohol drinking.

Nonpharmacological cues associated with drug intake may influence subjective and reinforcing effects of those drugs. Social drinkers (N = 80) participated in 2 sessions in which they rated and then consumed ad lib their preferred beer (with participants blind to brand). Visual and olfactory stimuli were obscured during 1 session (blocked) and not obscured during the other (unblocked). Dependent measures included ratings of "liking", "want another", and "desire to drink"; subjective mood; and ad lib beer consumption (reinforcement). Most ratings and ad lib consumption were lower during the blocked versus the unblocked condition. There were no interactions of blockade condition with sex and no effect of blockade on mood. These findings show that nonpharmacological stimuli associated with alcohol consumption influence alcohol's subjective and reinforcing effects.

Adult↗

PubMed2000

Enrichment induces structural changes and recovery from nonspatial memory deficits in CA1 NMDAR1-knockout mice.

We produced CA1-specific NMDA receptor 1 subunit-knockout (CA1-KO) mice to determine the NMDA receptor dependence of nonspatial memory formation and of experience-induced structural plasticity in the CA1 region. CA1-KO mice were profoundly impaired in object recognition, olfactory discrimination and contextual fear memories. Surprisingly, these deficits could be rescued by enriching experience. Using stereological electron microscopy, we found that enrichment induced an increase of the synapse density in the CA1 region in knockouts as well as control littermates. Therefore, our data indicate that CA1 NMDA receptor activity is critical in hippocampus-dependent nonspatial memory, but is not essential for experience-induced synaptic structural changes.

Animals↗

PubMed2003

NMDA lesions of Ammon's horn and the dentate gyrus disrupt the direct and temporally paced homing displayed by rats exploring a novel environment: evidence for a role of the hippocampus in dead reckoning.

Dead reckoning, a form of navigation used to locate a present position and to return to a starting position, is used by rats to return to their home base. The present experiment examined whether dead reckoning is displayed by rats during their first exploratory excursions in a novel environment and also examined whether the behaviour requires the integrity of the cells of the hippocampus. Experimental rats, those with NMDA (N-methyl d-aspartate) lesions of Ammon's horn and the dentate gyrus, and control rats could leave a cage to explore a large circular table under light and dark conditions. Home base behaviour, use of olfactory cues, and thigmotaxic- based navigation were evaluated. Temporal, topographical and kinematic analyses were conducted on the first three exploratory excursions that extended at least halfway across the table. Groups did not differ in numbers of exits from the home base, lingering near the home base, distance travelled, or the use of surface cues as might be exemplified by thigmotaxic and olfactory behaviour. Temporal, topographical and kinematic reconstructions of homing behaviour, however, indicated that control rats, but not hippocampal rats, made direct high velocity return trips to the home base in both the light and the dark. Peak velocity of the trips occurred at the trip midpoint, independent of trip distance, suggesting the movements were preplanned. These results are discussed in relation to the ideas that dead reckoning is used in the homing of exploring rats and that this form of navigation involves the hippocampus.

Animals↗

PubMed2006

What people believe about memory.

Two representative samples of adult Norwegians (n=2000) were asked a set of general and specific questions regarding their beliefs and opinions about human memory. The results indicate that on many questions, such as time of the earliest memories, inhibiting effects of collaboration, and memory for dramatic versus ordinary events, the views of the general public concurred with current research findings, and people in general had realistic views about their own memory performance. On other questions, such as the reliability of olfactory as compared with visual and auditory memory, the memory of small children in comparison with that of adults, the likelihood of repression of adult traumatic memories, and on more general questions such as the possibility of training memory and the capacity limitations of long-term memory, a large proportion of the participants expressed views that are less supported by scientific evidence. Implications of these findings are briefly discussed.

Adult↗