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PubMed2002

Stimulating effects of the insecticide chlorpyrifos on host searching and infestation efficacy of a parasitoid wasp.

Hymenopterous parasitoids play an important role in the control of insect populations. During oviposition, Hymenopterous parasitoids use cues such as odours from their environment to locate their specific host. Leptopilina heterotoma (parasitoid of Drosophila larvae) locate their host by probing the substrate with the ovipositor. This behaviour can be induced by the odour of the host substrate alone. We analysed the sub-lethal effects of chlorpyrifos at LD20 on the probing activity in response to a fruit odour (banana). The insecticide increased the percentage of females spontaneously probing in response to the odour. Parasitoid females were then conditioned to associate banana odour with the oviposition in host larvae. This conditioning enables parasitoids to memorize the odour and to increase their probing response to this odour. During the olfactory conditioning, females exposed to the insecticide found and oviposited in host larvae more quickly than control females. One hour after the olfactory conditioning, females exposed to the insecticide presented a higher increase of their probing response to the odour than controls. Twenty-four hours after conditioning, the stimulation produced by chlorpyrifos was no longer perceptible, but the level of response of conditioned females was still higher than that of non-conditioned females, showing that odour memory was not impaired by the insecticide treatment. These sub-lethal effects, that stimulate host searching by parasitoids without impairing odour memorization, could increase their parasitic efficiency.

Animals↗
PubMed1998

How We Smell: The Molecular and Cellular Bases of Olfaction.

Three models for the perception of odor molecules are suggested for the first time by experimental data. These studies illustrate how the nose may smell. Moreover, they suggest additional role(s) for odor receptors within and outside the olfactory system.

Journal Article↗
PubMed1991

Consequences of removing the vomeronasal organ.

In the last decade, research in our laboratories has focused on the effects of deafferentation of the mammalian chemosensory vomeronasal organ (VNX). Many different assays have been conducted and the results of some are briefly reviewed in this contribution, including the effects of VNX on neuroanatomical assessments using histochemistry (lectin binding) and immunohistochemistry (LHRH), male mouse and prairie vole ultrasonic vocalizations and hormone surges in response to cues from females, male mouse courtship and sexual behavior, territorial marking and inter-male aggression, the production of a puberty-altering substance found in mice, activation of reproduction in female voles (who generally do not exhibit estrous cycles) and maternal behaviors by female mice, including aggression directed toward intruder males. In some instances, the otherwise detrimental effects of VNX can be overcome by experience prior to deafferentation, especially in assays that are dependent upon expressions of behavior. In other situations, experience may have little impact on amelioration of the effects of VNX. The essential conclusions of this work focus our attention on reproductive physiology and behavior and a role for the vomeronasal organ in the perception of pheromones that modulate these functions.

Animals↗
PubMed2004

Socially mediated alcohol preferences in adolescent rats following interactions with an intoxicated peer.

This study focuses on "passive social influences" (alcohol-related information acquired by an organism that interacts with an intoxicated counterpart) that can potentially affect alcohol preference in adolescent rats. Five experiments were conducted to investigate whether repeated social interactions with an intoxicated peer can generate alcohol-related memories that lead an animal to exhibit heightened alcohol olfactory preference patterns. Juvenile experiences with alcohol were operationalized as follows: interactions with an alcohol-intoxicated peer (Experiment 1), with an alcohol-scented cotton surrogate (Experiment 2) or with an anesthetized alcohol-intoxicated partner (Experiments 3-5). Periadolescents were then evaluated in a two-way location olfactory test where they had the opportunity to investigate a hole scented with alcohol odor or vanilla (an odorant naturally preferred by the strain of rats here utilized). Only juveniles that interacted with an alcohol-intoxicated peer were found to exhibit a significant change in alcohol odor preferences when compared to appropriate controls that interacted with a non-intoxicated peer. Alcohol odor exposure alone or interactions with an anesthetized alcohol-intoxicated peer were not sufficient to establish changes in preference for alcohol sensory cues. Results indicate that social interactions with an intoxicated peer determine heightened preference for alcohol cues in periadolescents. The establishment of this preference seems to require behavioral manifestations of the intoxicated counterpart, instead of just being dependent on an olfactory pre-exposure to alcohol cues.

Alcohol Drinking↗
PubMed1996

Intranasal chemoreception in patients with multiple chemical sensitivities: a double-blind investigation.

Multiple chemical sensitivities (MCS) has become an increasingly frequent diagnosis assigned to patients with symptoms associated with exposures to environmental chemicals. Since the characteristic symptoms of MCS are triggered by very low concentrations of chemicals, in the range of olfactory thresholds, it is widely believed that the intranasal chemoreceptive senses are involved in the pathophysiology of MCS. Thus, the present study addressed both the olfactory and trigeminal systems: using a double-blind approach we investigated whether MCS patients show differences in responses after exposure to either room air or low concentrations of a widely used chemical agent (2-propanol). A total of 23 patients participated in the experiments (mean age 47 years; 13 female, 10 male). MCS was diagnosed according to Cullen's criteria Performance of the nasal chemical senses was established by means of chemosensory event-related potentials (CSERP) and subjective measures of olfactory function (odor discrimination, phenylethyl alcohol odor thresholds). CSERP were recorded in response to olfactory (H2S), and trigeminal (CO2) stimuli. The study provided three major results: (1) Approximately 20% of patients diagnosed with MCS presented symptoms regardless of the type of challenge, suggesting the susceptibility of MCS patients to unspecific experimental manipulations. (2) Changes in CSERP latencies indicated a change in the processing of both olfactory and trigeminal stimuli. (3) While odor threshold remained unchanged, the patients' ability to discriminate odors decreased after exposure to room air. In contrast, this decrease was less pronounced after exposure to 2-prop. Summarily, MCS patients respond to challenge with 2-prop with changes of chemosensory perception which might increase their susceptibility to environmentally volatile chemicals. Changes in the pattern of event-related potentials are interpreted as the possible change of the orientation of cortical generators, i.e., neuronal populations that were involved in the processing of chemosensory information. However, investigations in healthy controls are needed in order to draw further conclusions.

1-Propanol↗
PubMed2003

Taste-olfactory convergence, and the representation of the pleasantness of flavour, in the human brain.

The functional architecture of the central taste and olfactory systems in primates provides evidence that the convergence of taste and smell information onto single neurons is realized in the caudal orbitofrontal cortex (and immediately adjacent agranular insula). These higher-order association cortical areas thus support flavour processing. Much less is known, however, about homologous regions in the human cortex, or how taste-odour interactions, and thus flavour perception, are implemented in the human brain. We performed an event-related fMRI study to investigate where in the human brain these interactions between taste and odour stimuli (administered retronasally) may be realized. The brain regions that were activated by both taste and smell included parts of the caudal orbitofrontal cortex, amygdala, insular cortex and adjoining areas, and anterior cingulate cortex. It was shown that a small part of the anterior (putatively agranular) insula responds to unimodal taste and to unimodal olfactory stimuli, and that a part of the anterior frontal operculum is a unimodal taste area (putatively primary taste cortex) not activated by olfactory stimuli. Activations to combined olfactory and taste stimuli where there was little or no activation to either alone (providing positive evidence for interactions between the olfactory and taste inputs) were found in a lateral anterior part of the orbitofrontal cortex. Correlations with consonance ratings for the smell and taste combinations, and for their pleasantness, were found in a medial anterior part of the orbitofrontal cortex. These results provide evidence on the neural substrate for the convergence of taste and olfactory stimuli to produce flavour in humans, and where the pleasantness of flavour is represented in the human brain.

Brain↗
PubMed2004

Taste perception and coding in Drosophila.

BACKGROUND: Discrimination between edible and contaminated foods is crucial for the survival of animals. In Drosophila, a family of gustatory receptors (GRs) expressed in taste neurons is thought to mediate the recognition of sugars and bitter compounds, thereby controlling feeding behavior. RESULTS: We have characterized in detail the expression of eight Gr genes in the labial palps, the fly's main taste organ. These genes fall into two distinct groups: seven of them, including Gr66a, are expressed in 22 or fewer taste neurons in each labial palp. Additional experiments show that many of these genes are coexpressed in partially overlapping sets of neurons. In contrast, Gr5a, which encodes a receptor for trehalose, is expressed in a distinct and larger set of taste neurons associated with most chemosensory sensilla, including taste pegs. Mapping the axonal targets of cells expressing Gr66a and Gr5a reveals distinct projection patterns for these two groups of neurons in the brain. Moreover, tetanus toxin-mediated inactivation of Gr66a- or Gr5a-expressing cells shows that these two sets of neurons mediate distinct taste modalities-the perception of bitter (caffeine) and sweet (trehalose) taste, respectively. CONCLUSION: Discrimination between two taste modalities-sweet and bitter-requires specific sets of gustatory receptor neurons that express different Gr genes. Unlike the Drosophila olfactory system, where each neuron expresses a single olfactory receptor gene, taste neurons can express multiple receptors and do so in a complex Gr gene code that is unique for small sets of neurons.

Animals↗
PubMed2001

Phosphorylation of voltage-gated ion channels in rat olfactory receptor neurons.

In olfactory receptor neurons (ORNs), ligand-odorant receptor interactions cause G protein-mediated activation of adenylate cyclase and a subsequent increase in concentration of the intracellular messenger cAMP. Odorant-evoked elevation in cAMP is thought to directly activate a cation-selective cyclic nucleotide-gated channel, which causes external Ca2+ influx, leading to membrane depolarization and the generation of action potentials. Our data show that in freshly dissociated rat ORNs, odorant-induced elevation in cAMP also activates cAMP-dependent protein kinase (PKA), which is then able to phosphorylate various protein targets in the olfactory signal transduction pathway, specifically voltage-gated sodium and calcium channels. The presence of PKI (PKA inhibitor peptide) blocked the modulatory action of cAMP on voltage-gated ion channels. By modulating the input/output properties of the sensory neurons, this mechanism could take part in the complex adaptation process in odorant perception. In addition, we found modulation of voltage-gated sodium and calcium channel currents by 5-hydroxytryptamine and the dopamine D1 receptor agonist SKF 38393. These findings suggest that in situ ORNs might also be a target for efferent modulation.

Animals↗
PubMed2005

Chemosensory perception and event-related potentials in self-reported chemical hypersensitivity.

Anormal chemosensory perception has been identified as a possible mechanism underlying odor intolerance, but research in this domain has yet been rather limited. The main objective of the present study was to investigate total perceived intensity, unpleasantness, sensory irritation, and cortical activity assessed with chemosensory event-related potentials (ERPs) for three concentrations of pyridine ranging from predominantly olfactory to trigeminal in activation. Results from 19 individuals with self-reported chemical hypersensitivity and 19 controls with self-reported normal chemical sensitivity show that the hypersensitive group, compared to controls, rated the pyridine stimuli to be more intense and unpleasant, and that these group differences increased with pyridine concentration. Sensory irritation was also the perceptual dimension found to correlate strongest with score on the chemical sensitivity scale. However, no group differences were found in ERP amplitudes or latencies. These findings suggest that self-reported chemical hypersensitivity (1) can be associated with anormal chemosensory perception, (2) may be more closely related to trigeminal function than to olfaction, and (3) has a neural basis at a higher cortical level than that captured by chemosensory ERPs.

Adult↗
PubMed2000

Perception of female reproductive state from vocal cues in a mammal species.

While acoustic signalling by males is known to affect male-male competition, mate attraction and the timing of ovulation, the extent to which sexual selection has shaped the evolution of female acoustic signals is poorly understood. Among mammals, experimental evidence indicates that females attract mating partners by using olfactory and visual signals to advertise their reproductive state. Whether or not males ascertain female reproductive state from vocal signals has, however, never been systematically tested. In this study, we use playbacks of recorded vocalizations to demonstrate that male Barbary macaques, Macaca sylvanus, can discriminate between female copulation calls given at different stages of the oestrous cycle, responding more strongly to those given around the time when conception is most likely to occur. Acoustic analysis suggests that the mean dominant frequency of call units and a number of temporal parameters could provide males with the information necessary to discern the proximity of ovulation in this way Our results provide the first experimental evidence that the calls of female mammals may contain information on reproductive state, which males can perceive and use in such a way as to increase their reproductive success.

Animals↗
PubMed2001

Toward an interpretation of dynamic neural activity in terms of chaotic dynamical systems.

Using the concepts of chaotic dynamical systems, we present an interpretation of dynamic neural activity found in cortical and subcortical areas. The discovery of chaotic itinerancy in high-dimensional dynamical systems with and without a noise term has motivated a new interpretation of this dynamic neural activity, cast in terms of the high-dimensional transitory dynamics among "exotic" attractors. This interpretation is quite different from the conventional one, cast in terms of simple behavior on low-dimensional attractors. Skarda and Freeman (1987) presented evidence in support of the conclusion that animals cannot memorize odor without chaotic activity of neuron populations. Following their work, we study the role of chaotic dynamics in biological information processing, perception, and memory. We propose a new coding scheme of information in chaos-driven contracting systems we refer to as Cantor coding. Since these systems are found in the hippocampal formation and also in the olfactory system, the proposed coding scheme should be of biological significance. Based on these intensive studies, a hypothesis regarding the formation of episodic memory is given.

Brain↗
PubMed2003

The wave packet: an action potential for the 21st century.

Sensing and perceiving involve enormous numbers of widely distributed dendritic and action potentials in cortex, before, during and after stimulus arrival but with differing spatiotemporal patterns. Stimulus-activated receptors drive cortical neurons directly (olfactory) or indirectly through thalamocortical relays. The driven activity induces hemisphere-wide, self-organized patterns of neural activity called wave packets. Three levels of brain function are hypothesized to mediate transition from sensation and perception. Microscopic activity expressed by action potentials is sensory. Macroscopic activity of the whole forebrain expressed by behavior is perceptual. Mesoscopic activity bridges the gap by the formation of wave packets. They form when sensory input destabilizes the primary receiving areas by local state transitions. The sensory-driven action potentials condense into mesoscopic wave packets like molecules forming raindrops from vapor. The condensation disks sustain 2D spatial patterns of phase and amplitude of carrier waves in the beta and gamma EEG. The AM patterns correlate not with features but with the context and value of sensory stimuli for the subjects, in a word, their meaning. The wave packets from all sensory areas are broadly transmitted through the forebrain. They induce the formation of macroscopic patterns that coalesce like scintillating pools over much and perhaps all of each hemisphere. The prediction is made for clinical testing that wave packets are precursor to states of awareness. They are not by themselves accessible to experience, as may be the macroscopic states initiated by global state transitions.

Cerebral Cortex↗
PubMed2000

[Study of the olfactory response in the Drosophila homeotic mutant leg-aristae-wing complex gene].

Antennae are known to be olfactory organs in Drosophila. The leg-aristae-wing complex (lawc) mutation causes a homeotic transformation of the arista (the fifth element of antenna) into tarsal elements. To test how the homeotic transformation of the arista into the tarsus can affect behavior, we studied the olfactory response in the lawc mutants. The data were carefully processed by statistical methods. In spite of a low penetrance of the trait of arista transformation, the mutant flies were found to be approximately half as perceptible to attractant odors than the wild-type flies.

Animals↗
PubMed1978

Models of the dynamics of neural populations.

Three requirements are posed for constructing models to simulate EEG dynamics. The element of the model should be an interactive ensemble of neurons and not single neurons. The observations must be statistical, such as EEG waves and averages of unit activity over time and over local neighborhoods containing neural subsets. The state variables and operations of the model must be clearly related to behavioral functions such as sensory reception and perception. A model is presented that exemplifies these requirements. Its key feature is the dependence of its levels of interaction on the level of its input, so that with each burst of input the model switches from an equilibrium state to a limit cycle state. A mechanism is described for coding sensory input into the spatial modulation of the limit cycle activity viewed as a carrier. It is suggested that sensory recepts and percepts exist at different hierarchical levels in the brain, recepts at the level of single neurones, and percepts at the level of neural ensembles, the latter being possibly manifested in the EEG.

Animals↗
PubMed1982

Modulation of agonistic behavior by the dual olfactory system in male mice.

This study analyzed the effects of deafferentation of the main, vomeronasal or both olfactory systems on the agonistic behavior of male mice in response to unfamiliar male intruder mice. In every animal, regardless of the technique used, disruption of the vomeronasal system led to consistent reductions in agonistic behavior. All animals receiving bulbectomies, vomeronasal tract transections or a combined treatment of vomeronasal cuts and ZnSO4 nasal flush reliably suppressed agonistic responding toward the intruder. Animals treated with intranasal ZnSO4 alone or those receiving control procedures continued to respond to the intruders at rates similar to pretreatment. These results indicate that the vomeronasal system is directly involved in the perception of the male chemosignals modulating agonistic behavior and, therefore, is capable of modulating the male's response to these signals.

Aggression↗
PubMed2001

Perception and pleasantness of a food with varying odor and flavor among the elderly and young.

Aging diminishes chemosensory functioning, in particular the sense of smell, thus possibly decreasing the enjoyment from food. We examined the effect of age on ortho- and retronasal perception and on pleasantness ratings of cream cheese in which 3 levels of food aromas (vanilla or basil) were combined, respectively, with 3 levels of sucrose or NaCl. The elderly (n=59, 60-85 years) and young (n=39, 21-38 years) subjects were also tested for olfactory identification ability. As expected, the young differentiated odor intensities better than the elderly. The sucrose and NaCl levels affected overall flavor intensity and pleasantness similarly in both age groups. The flavor of vanilla, but not that of basil, was favored by the elderly, suggesting that strong flavor in an appropriate context can improve the hedonic quality. The odor identification declined with age in the elderly and on average, it was lower in the elderly than in the young. Ability to identify odors was not associated with ratings of odor intensities.

Adult↗
PubMedDate not supplied

[Complex perception of stimuli during conditioning].

The review concerns the effects of a variety of stimuli on the reproduction of conditioned reflexes. By the literature data, during conditioning of any type, besides the single stimulus intentionally applied by an experimenter as a conditioned one, an animal perceives the whole complex of stimuli (acoustic, visual, olfactory, algesic, and other exteroceptive, proprioceptive, and interoceptive stimuli), including those of the environment and time of the day during training. Many of these stimuli are essential for the reproduction of the acquired habit. The complex of stimuli that act on an animal during the reproduction should in all parameters correspond to that perceived by the animal during training. If the complexes differ at least in one stimulus, the reproduction of the reflex may fail.

Animals↗