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PubMed2003

The evolutionary origin of the mammalian isocortex: towards an integrated developmental and functional approach.

The isocortex is a distinctive feature of mammalian brains, which has no clear counterpart in the cerebral hemispheres of other amniotes. This paper speculates on the evolutionary processes giving rise to the isocortex. As a first step, we intend to identify what structure may be ancestral to the isocortex in the reptilian brain. Then, it is necessary to account for the transformations (developmental, connectional, and functional) of this ancestral structure, which resulted in the origin of the isocortex. One long-held perspective argues that part of the isocortex derives from the ventral pallium of reptiles, whereas another view proposes that the isocortex originated mostly from the dorsal pallium. We consider that, at this point, evidence tends to favor correspondence of the isocortex with the dorsal cortex of reptiles. In any case, the isocortex may have originated partly as a consequence of an overall "dorsalizing" effect (that is, an expansion of the territories expressing dorsal-specific genes) during pallial development. Furthermore, expansion of the dorsal pallium may have been driven by selective pressures favoring the development of associative networks between the dorsal cortex, the olfactory cortex, and the hippocampus, which participated in spatial or episodic memory in the early mammals. In this context, sensory projections that in reptiles end in the ventral pallium, are observed to terminate in the isocortex (dorsal pallium) of mammals, perhaps owing to their participation in these associative networks.

Anatomy, Comparative↗

PubMedDate not supplied

[Electron microscopic study of Haller's organ in the tick, Ixodes persulcatus (Ixodidae)].

Haller's organ consists of the capsule, in which are arranged 7 thin-walled porous olfactory hairs, and an anterior group of sensillae situated in the cuticular recess before the capsule. The anterior group is represented by one thick-walled porous, one conical, two thin and two grooved hairs. The porous hairs are characterized by "plugs", the grooved ones--by a complex system of cavities and tubules. Before the organ there are hairs resembling tactile and gustatory receptors of arthropods, behind the organ there arrange hairs with a system of cavities and tubules. Sensible elements of all sensillae studied are bipolar receptor cells bearing one modified cilium on the surface of peripheral processes. The details of the structure of perceptive and accessory apparatus of the above receptors were investigated.

Animals↗

PubMed2000

The molecular receptive range of an odorant receptor.

An odor perception is the brain's interpretation of the activation pattern of many peripheral sensory neurons that are differentially sensitive to a wide variety of odors. The sensitivity of these neurons is determined by which of the thousand or so odor receptor proteins they express on their surface. Understanding the odor code thus requires mapping the receptive range of odorant receptors. We have adopted a pharmacological approach that uses a large and diverse pool of odorous compounds to characterize the molecular receptive field of an odor receptor. We found a high specificity for certain molecular features, but high tolerance for others-a strategy that enables the olfactory apparatus to be both highly discriminating, and able to recognize several thousand odorous compounds.

Aldehydes↗

PubMed1994

Drug effects in a radial maze designed for dissociation of cues used by mice.

Scopolamine and amphetamine effects were investigated in a new radial maze. Three distinct procedures were designed to dissociate the use, by C57BL/6 mice, of the different cues available: a procedure where only spatial information was available, a procedure in which both spatial cues and olfactory trials were present, and a nonconfinement procedure where mice could use spatial cues, olfactory trials, and/or algorithmic strategies. We found that while scopolamine impaired performance on the maze in all three procedures, amphetamine tended to improve solving of the maze problem, but only in the procedure where spatial cues alone were available. The results are discussed in relation to hypotheses concerning these drug effects.

Algorithms↗

PubMed1996

Relationship between odor perception and depression in the Japanese elderly.

Odor perception has been studied in patients with various mental disorders; however, no consensus has been reached as to its detection, identification, or pleasantness/unpleasantness of odors especially in patients with depression. One hundred and nineteen normal elderly individuals living at home were exposed to odors of rose, perfume, white ginger, Indian ink, cigarette smoke, milk, feces and orange scent using the scratch and sniff method. They were asked to rate the strength of each odor, its pleasantness or unpleasantness, their liking for it, and their familiarity with it. They were also asked to complete a self-rating depression scale (SDS). The relationship of the score of each psychological olfactory scale with the SDS score and the difference in the score of each psychological scale between high-SDS and low-SDS groups are discussed.

Aged↗

PubMed2002

Dual antennular chemosensory pathways mediate odor-associative learning and odor discrimination in the Caribbean spiny lobster Panulirus argus.

Chemosensory neurons in the antennular flagella of lobsters mediate long-range responses to chemicals. These neurons are part of two parallel chemosensory pathways with different peripheral and central components. Aesthetasc sensilla on the lateral flagella are innervated by chemosensory neurons that project to the olfactory lobes. A diversity of other 'non-aesthetasc' sensilla on both lateral and medial flagella are innervated by mechano- and chemosensory neurons, and most of these non-aesthetasc neurons project to the lateral antennular neuropils. We investigated the roles of these two pathways in odor-associative learning and odor discrimination by selectively removing either aesthetasc or non-aesthetasc sensilla from the spiny lobster Panulirus argus. Lobsters lacking both aesthetasc and non-aesthetasc antennular sensilla show very reduced or no odor-mediated searching behavior. We associatively conditioned lobsters using two paradigms: aversive conditioning with generalization testing (which reveals the similarity in the lobsters' perception of odorants) and discrimination conditioning (which reveals the lobsters' ability to discriminate odorants). Sham-control intact lobsters performed these tasks well, as did lobsters lacking either aesthetascs or non-aesthetasc setae. There was a strong but statistically non-significant trend that lobsters lacking either aesthetascs or non-aesthetasc setae generalized more between complex odor mixtures than did intact lobsters. After aversive conditioning with generalization testing, aesthetasc-ablated lobsters had more difficulty discriminating among the most closely related complex mixtures than did intact or non-aesthetasc-ablated lobsters. However, after discrimination conditioning, aesthetasc-ablated lobsters were as proficient as intact animals in discriminating highly similar mixtures. These results indicate overlap and redundancy in the function of these two chemosensory pathways in odor-associative learning and odor discrimination, but these pathways also complement each other to enable better discrimination. This study presents the first evidence for a role of non-aesthetasc chemosensory neurons in complex odor-mediated behaviors such as learning and discrimination.

Animals↗

PubMed2005

Examination of the influence of personal traits and habituation on the reporting of complaints at experimental exposure to ammonia.

OBJECTIVE: The aim of the study is to examine the impact of personal traits and habituation on the intensity of self reported health symptoms and complaints. METHODS: Forty-three healthy male volunteers were exposed to ammonia vapours in concentrations of 0, 10, 20, 20/40, and 50 ppm on five consecutive days. To explore a possible influence of habituation on the perception of symptoms, the study group was divided into 30 men who were not familiar with the smell of ammonia, and ten participants regularly exposed to ammonia at the workplace. The perceived acute health symptoms and self-reported changes of well-being were assessed by the German version of a questionnaire of the Swedish Performance Evaluation System (SPES). Personal traits were ascertained with the positive and negative affectivity schedule (PANAS) and the Freiburger Persönlichkeits Inventar (FPI). RESULTS: There are significant associations between personal traits and the amount of complaints. Subjects with high positive affectivity report less respiratory and irritative complaints, whereas persons with negative affectivity report significantly more olfactory and respiratory symptoms. In general, the strength of these correlations decreases with higher exposure levels. At ammonia concentration above 20 ppm, these associations were no more statistically significant. During the daily exposures, the score of symptoms did not vary significantly. The perceived intensity of health symptoms and annoyance increased with the concentration of ammonia, while the self-reported dimensions of well-being decreased. Workers familiar with the smell of ammonia vapours reported less symptoms compared to naïve subjects. CONCLUSIONS: Habituation to ammonia vapours as well as personal traits influence the reporting of complaints particularly at low exposure. Both factors should be considered in the examination of chemosensory irritative compounds.

Adult↗

PubMed1997

Influence of olfactory stimulation on nociceptive behavior in mice.

The reactions elicited by nociceptive stimulations were studied in mice exposed to the presence of different odors: positive (attractive), negative (aversive), or neutral. In a first set of experiments, the animals were not habituated to the odors before the nociceptive stimuli were applied; in this case, the olfactory environment during experienced pain had essentially no effect on the nociceptive reactions, whatever the nature of the odors. In a second set of experiments, the animals were habituated to the same odor for 20 days. The control group consisted of mice habituated to and tested in the presence of the odor of the laboratory. In that case, compared to controls, the neutral odor had no influence on nociceptive reactions. By contrast, the positive odor decreased and the negative odor increased the reactions, especially when the intensity of the nociceptive stimulus was low. Moreover, it has been shown that the reactions elicited during a second nociceptive stimulation period depend on the perception of pain animals experience during the first stimulation, which depended, in turn, on the odor associated with it. Results are discussed in terms of opioid-mediated interactions between olfaction and pain.

Animals↗

PubMed2002

How lobsters, crayfishes, and crabs locate sources of odor: current perspectives and future directions.

Olfactory orientation poses many challenges for crustaceans in marine environments. Recent behavioral experiments lead to a new understanding of the role of multiple sensory appendages, whereas application of non-invasive chemical visualization techniques and biomimetic robotics have allowed researchers to correlate the stimulus environment with behavior and to directly test proposed orientation mechanisms in decapod crustaceans.

Animals↗

PubMed2000

Quantification of odor quality.

The relationship between odor quality and molecular properties is arguably the most important issue in olfaction. Despite sophistication in the chemical characterization of molecules, accompanying perceptual characterization has had little quantitative usefulness, relying mostly on enumerative description. As a result of weak interest in the topic outside industry and little agreement regarding how to measure quality, the field of olfactory psychophysics has failed to develop a substantial database for odor quality and has offered little help to other researchers, e.g. neurobiologists, in choice of stimuli, interpretation of outcome or testable hypotheses. This review scrutinizes how psychophysicists and others have measured quality and offers criteria for useful techniques. Most measures have had a subjective component that makes them anachronistic with modern methodology in experimental behavioral science, indeterminate regarding the extent of individual differences, unusable with infrahumans and of unproved ability to discern small differences. Techniques based upon performance, rather than on the more common reporting of mental content, offer firmer possibilities for growth. These techniques inevitably tap the discriminative basis of perception. The nonsubjective techniques have high sensitivity, can have counterparts in infrahuman research, are suitable to examine individual differences and yield non-negotiable answers with potential archival value. Discriminative techniques have their limitations, too-principally excess sensitivity that abridges their use to comparisons between similar-smelling stimuli. Research has begun to extend that range and may overcome the limitation. Application of discriminative methods may have the side-effect of shifting focus in structure-activity research from searches for molecular least common denominators that underlie often vague similarity to the search for molecular properties of importance in discrimination of small differences.

Humans↗

PubMed2005

Lead exposure and (n-3) fatty acid deficiency during rat neonatal development affect subsequent spatial task performance and olfactory discrimination.

Docosahexaenoic acid [22:6(n-3), DHA] is important for optimal infant central nervous system development, and lead (Pb) exposure during development can produce neurological deficits. Long-Evans strain rats were fed either an (n-3) deficient [(n-3) Def] diet to produce brain DHA deficiency, or an adequate [(n-3) Adq] diet through 2 generations. At the birth of the 2nd generation, the dams were subdivided into 4 groups and supplied drinking water containing either 5.27 mmol/L (Pb) or sodium (Na) acetate until weaning. Rats were killed at 3 wk (weaning) and 11 wk (maturity) for brain Pb and fatty acid analysis. Spatial task and olfactory-cued behavioral assessments were initiated at 9 wk. Rats in the (n-3) Def group had a 79% lower concentration of brain DHA compared with the (n-3) Adq group with no effect of Pb exposure. At weaning, Pb concentrations were 7.17 +/- 0.47 nmol Pb/g of brain (wet weight) in the (n-3) Adq-Pb group and 6.49 +/- 0.63 nmol Pb/g of brain (wet weight) in the (n-3) Def-Pb group. At maturity, the brains contained 1.30 +/- 0.22 and 1.07 +/- 0.12 nmol Pb/g (wet weight), respectively. In behavioral testing, significant effects of both Pb and DHA deficiency were observed in the Morris water maze probe trial and in 2-odor olfactory discrimination acquisition and olfactory-based reversal learning tasks. Both lactational Pb exposure and (n-3) fatty acid deficiency led to behavioral deficits with additive effects observed only in the acquisition of 2-odor discriminations.

Aging↗

PubMed1984

Psychomotor epileptic symptoms in six patients with bipolar mood disorders.

Of 12 consecutive patients with bipolar mood disorders satisfying DSM-III criteria, six were discovered to have five or more psychomotor epileptic symptoms. All of the six had olfactory hallucinations, metamorphopsias, and multiple déjà vu or mystical experiences. Each of them responded to lithium carbonate and had a first-degree relative with a bipolar disorder. The authors suggest that psychomotor symptoms may be more prevalent in bipolar patients than has hitherto been recognized.

Adult↗

PubMed2004

Use of visual, acoustic, and olfactory information during embedded invertebrate foraging in brown capuchins (Cebus apella).

Experiments were conducted to investigate which sensory cues are used by brown capuchins (Cebus apella) in embedded invertebrate foraging. The importance of visual, olfactory, and acoustic cues in such foraging was determined by presenting subjects with a stimulus log modified to block out given sensory cues. Experiment 1 was designed to investigate whether subjects could locate an invertebrate embedded in wood when only visual, acoustic, or olfactory information was available. Experiments 2 and 3 were designed to investigate extractive foraging behavior when two sensory cues were provided. It was hypothesized that the combination of visual and acoustic information would be necessary for subjects to successfully locate embedded invertebrates. Results indicated that subjects' performance was most successful when both visual and acoustic information was available.

Animals↗

PubMed2000

Interaction of visual and olfactory cues in the aggregation behaviour of the haematophagous bug Triatoma infestans.

We analysed how the assembling behaviour of Triatoma infestans is modulated by the convergence of chemical cues released by their faeces and the spectral quality of the light associated with refuges. Second-instar larvae were confronted with refuges associated with a visual stimulus (either blue, green or red lights having the same intensity, or darkness) and a chemical cue (presence or absence of faeces). In this context, faeces constitute a major attractant for bugs. In the absence of faeces, bugs always assembled in dark places. Green light was always rejected despite the presence of faeces, i.e. the assembling behaviour was controlled by a photonegative reaction to this light. In the presence of red light, orientation towards the chemical cue dominated over the bugs' photonegative reaction to this light. Such a light was avoided in the absence of faeces but not in their presence. Also, negative phototaxis to blue light could be counteracted by the presence of the chemical cue. Thus, a concrete interaction between visual and olfactory cues occurred in these experiments: the bugs' response changed depending on the specific combination of spectral light and faeces. Finally, bugs responded differentially to blue, red and green lights of the same intensity. They assembled preferentially on red, followed by blue and then by green. Thus, discrimination between lights of different spectral quality is possible, probably through an achromatic mechanism.

Animals↗

PubMed2004

Contextual taste cues modulate olfactory learning in C. elegans by an occasion-setting mechanism.

Manipulations of context can affect learning and memory performance across species in many associative learning paradigms. Using taste cues to create distinct contexts for olfactory adaptation assays in the nematode Caenorhabditis elegans, we now show that performance in this associative learning paradigm is sensitive to context manipulations, and we investigate the mechanism(s) used for the integration of context cues in learning. One possibility is that the taste and olfactory stimuli are perceived as a combined, blended cue that the animals then associate with the unconditioned stimulus (US) in the same manner as with any other unitary conditioned stimuli (CS). Alternatively, an occasion-setting model suggests that the taste cues only define the appropriate context for olfactory memory retrieval without directly entering into the primary association. Analysis of genetic mutants demonstrated that the olfactory and context cues are sensed by distinct primary sensory neurons and that the animals' ability to use taste cues to modulate olfactory learning is independent from their ability to utilize these same taste cues for adaptation. We interpret these results as evidence for the occasion-setting mechanism in which context cues modulate primary Pavlovian association by functioning in a hierarchical manner to define the appropriate setting for memory recall.

Adaptation, Physiological↗

PubMed2002

The effect of molecular structure on olfactory discrimination by the parasitoid Microplitis croceipes.

Flight chamber experiments were conducted to examine the capacity of the larval parasitoid Microplitis croceipes (Hymenoptera: Braconidae) to learn to distinguish between structurally related aliphatic alcohols differing in the carbon chain-length and the position of the functional group, and between an alcohol and the respective aldehyde. The parasitoid's ability to discriminate between the components depended on the chain-length of the alcohol to which they had been conditioned. Discrimination improved with increasing difference in carbon chain-length, e.g. the parasitoids made clear distinction between 1-hexanol and 1-octanol. Microplitis croceipes could also distinguish different isomers of six-carbon alcohols on the basis of the position of the alcoholic group as well as between 1-hexanol and 1-hexanal. The learning abilities of M. croceipes correspond to the specificity of antennal odour receptors towards aliphatic alcohols and aldehydes in previous electrophysiological studies of M. croceipes and other insects. Differences in perception or processing of single compounds might reflect differences of their ecological relevance.

1-Octanol↗

PubMed2006

Potential early markers of Parkinson disease in idiopathic REM sleep behavior disorder.

BACKGROUND: Idiopathic REM sleep behavior disorder (RBD) is characterized by loss of atonia during REM sleep, resulting in motor activity during dreams. Studies estimate that approximately half of patients with RBD will eventually develop Parkinson disease (PD), so RBD may be an indicator of presymptomatic PD. Several potential early diagnostic markers of PD have been proposed, but they have generally not been tested in presymptomatic PD. The authors hypothesized that these markers may be abnormal in idiopathic RBD. METHODS: The authors compared 25 patients with polysomnography-confirmed RBD without PD with age- and sex-matched controls. Color vision, olfaction, quantitative motor testing, and indices of depression, personality, and autonomic function were examined. RESULTS: Patients demonstrated significant impairment in color discrimination and olfactory function. Patients had subtle abnormalities on quantitative testing of motor and gait speed. Autonomic symptoms were more common in patients than controls. Abnormalities were heterogeneous, with some patients scoring normally on all domains, whereas others were severely impaired on multiple domains. Dysfunction on tests of olfactory function, color vision, and motor speed were highly correlated, such that patients who performed poorly on one test tended to perform poorly on the others. CONCLUSIONS: Many potential early markers of Parkinson disease are significantly abnormal in idiopathic REM sleep behavior disorder. These abnormalities are present in approximately half of the patients, suggesting a heterogenous pathophysiology.

Adult↗

PubMed1998

Lesions of the frontal cortex, hippocampus, and intralaminar thalamic nuclei have distinct effects on remembering in rats.

Lesions of the intralaminar thalamic nuclei (ILn), the medial wall (MW) area of prefrontal cortex, and the hippocampus were compared and found to have distinct effects on delayed matching-to-sample (DMS) and delayed non-matching-to-sample (DNMS) tasks based on different types of stimulus cues. Hippocampal lesions impaired DNMS trained in a radial arm maze but had little effect on DMS trained with retractable levers or olfactory DNMS. MW lesions affected the DMS task but had limited effects on olfactory DNMS and radial arm maze DNMS. ILn lesions resulted in a more generalized pattern of impairment for radial maze tasks and (in previous studies) for the DMS and olfactory DNMS tasks. Only the hippocampal lesion was associated with a delay-dependent impairment. It is argued that ILn lesions disrupt remembering through their effects on the recurrent, feedback pathways that link functionally related areas of the basal ganglia and cortex.

Analysis of Variance↗