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PubMedDate not supplied

Psychophysical methods in the study of olfaction and respiratory tract irritation.

This article describes the fundamentals of olfaction and irritation perception and the dominant psychophysical methods for the assessment of olfaction and respiratory tract irritation. It also discusses factors that determine the olfactory and irritant response (ranging from the physicochemical properties of the stimulus to the physiological and cognitive characteristics of the individual). Because the vast majority of volatile chemicals stimulate the olfactory system at concentrations well below that at which they will elicit trigeminal activation, the evaluation of irritation from volatiles is often confounded by the perception of odor. Several methods have been used for studying the perception of irritation, without the influence of olfaction. The perception and reports of acute adverse effects of odor, annoyance, and irritation from volatile chemicals have multiple determinants. Understanding the perceptual impact of chemicals under environmentally realistic conditions requires attending to both the sensory and the psychological impact of those exposures. The review, which is largely based on presentations given by Dr. Richard Doty and Dr. William Cain, concludes by discussing the importance of the psychophysical approach, which considers physiochemical, subject, experimental, and cognitive/ psychological factors, for research in the chemical senses.

Environmental Pollutants↗
PubMed2005

Distorted odorant perception: analysis of a series of 56 patients with parosmia.

OBJECTIVE: To characterize the self-reported olfactory and gustatory symptoms, olfactory function, and causes in parosmia. DESIGN: Assessment of olfactory symptoms and function in patients with a chief complaint of parosmia. SETTING: A university hospital clinic and research facility. PATIENTS: Fifty-six consecutive patients presented to the ORL Clinic, European Hospital Georges Pompidou, with a chief complaint of parosmia between October 2001 and November 2003. MAIN OUTCOME MEASURES: Subjective olfactory symptom analysis and olfactory function test results. RESULTS: The mean duration of parosmia was 63.0 months. Forty patients (71.4%) reported associated hyposmia and 16 (28.6%) reported anosmia. Olfactory testing revealed moderate to severe olfactory loss in all patients. Quantitative and qualitative alterations occurred simultaneously in 32 patients (57.1%); parosmia onset occurred within 3 months after quantitative dysosmia in 19 patients (33.9%) and after 3 months in 5 patients (8.9%). The sensation of parosmia was always unpleasant. The main odorant triggers eliciting parosmia are described. The mean severity of flavor dysfunction of the population, evaluated using a 10-cm visual analog scale, was 6.4. Thirty-one patients (55.4%) viewed their olfactory alteration as severely affecting their quality of life. The main clinical association of parosmia was upper respiratory tract infection, found in 42.8% of the patients. Others clinical associations are described. CONCLUSION: The series of patients with parosmia presented herein, the largest in the literature, permits a clinical description of this rare olfactory abnormality.

Adolescent↗
PubMed1986

Odor perception in temporal lobe epilepsy patients with and without temporal lobectomy.

The investigation employed monorhinic (single nostril) olfactory testing to decide whether patients with unilateral anterior temporal lobe resection (N = 16) and patients with unoperated temporal lobe epilepsy (N = 18) have impaired ability to detect, remember, and identify odors. A shape memory task accompanied the odor memory task for comparison. The lobectomy patients showed a minor bilateral depression of absolute sensitivity but still fell within the clinically normal range. The lobectomy patients showed impairment of odor recognition memory but strictly via the nostril ipsilateral to the resected lobe. A similar ipsilateral-contralateral asymmetry characterized the performance of these patients in odor identification. In that case, however, performance via the contralateral nostril showed some impairment too. Nonsurgery patients also exhibited some impairment in odor identification, but bilaterally. Finally, both groups of patients fell somewhat below normals in recognition memory for amorphous shapes. The various results implied that temporal lobe epilepsy alone takes some toll on olfactory information processing and that temporal lobe resection exacerbates the problem, but only on the side of surgery.

Adult↗
PubMed2002

Verbal versus olfactory cues: affect in elicited memories.

Verbal processing has a reduced role for olfactory stimuli. It is difficult to provide a label for an odor experience. Odor perception can retrieve memories of life events with personal meaning and elicit affective experiences. Odors that have emotionally loaded content could produce older memories. Common odors with well-known names have been used. In Exp. 1 the names were shown, and the subjects were asked to imagine the corresponding odors; subsequently those odorants were presented. In Exp. 2 at first the odorants were presented and subsequently their names, printed one each per white card. The subjects were requested to provide written free associations. At the end of each session they scored a semantic differential. The hypothesis that emotionally loaded associations are more frequent when evoked by odorants seems confirmed, supported also by some reliable differences between the profiles for olfactory verbal stimuli. The evaluation of olfactory stimuli did not differ from one experiment to the other; verbal stimuli, on the contrary, are differently evaluated if the corresponding odorants were presented before or after their labels.

Affect↗
PubMed1986

Homing pigeons subjected to section of the anterior commissure can build up two olfactory maps in the deflector lofts.

Pigeons kept in two cages with screens which deflect the wind clockwise (CW) or counter-clockwise (CCW) show corresponding deflections in their initial orientation. In order to determine the nature of this phenomenon, experimental birds were treated as follows: The anterior commissure of the forebrain (AC), which mediates the interhemispheric transfer of olfactory input was sectioned; After surgery, each experimental bird was kept alternately in a CW cage with its right nostril plugged, and in a CCW cage with its left nostril plugged; the two treatments were alternated every 3 days for 69 days before test releases began. In 23 out of 28 cases the experimentals showed CW deflections when released with the right nostril plugged and CCW deflections when released with the left nostril plugged. The controls were intact, and their nostrils were free in each phase of the experiment. They were subdivided into two groups: one group was kept in the CW cage when the experimentals were in the same cage, the other group in the CCW cage when the experimentals stayed there. In the remaining time each group was kept in a fenced loft. The behaviour of controls demonstrated that the time the experimentals had spent in each kind of deflector cage had been long enough to produce the corresponding deflections in initial orientation. Control experiments were then performed on pigeons with the AC sectioned (2 series) and on intact birds (1 series), both maintained in lofts which did not deflect the wind, and released with one nostril plugged. They did not show deflections similar to those of the experimentals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Circadian rhythm in olfactory response in the antennae controlled by the optic lobe in the cockroach.

The olfactory response in antennae of the cockroach, Leucophaea maderae, was investigated by measuring electroantennograms (EAGs) in restrained animals. The amplitude of the EAG response to pulses of ethyl acetate, octanol, or fenchone, exhibited a robust, light entrained, circadian rhythm that persisted at least 14 days in constant darkness. Dilution-response curves measured at the peak and trough of the rhythm indicated there was a 10-fold change in sensitivity. The EAG rhythm was abolished by severing the optic tracts, while entrainment was abolished by ablation of the compound eyes. The results indicate that the circadian system modulates olfactory sensitivity in the antennae and that the rhythm is driven by a circadian pacemaker in the optic lobes that is entrained by photoreceptors in the compound eyes.

Animals↗
PubMed1996

Mecamylamine-induced impairment of acquisition and retrieval of olfactory conditioning in the honeybee.

Mecamylamine, a nicotinic receptor antagonist, was injected into the honeybee brain haemolymph. The effects of the drug were investigated on Pavlovian conditioning of the proboscis extension reflex. The conditioned response was acquired after a one-trial learning session, consisting of an olfactory-conditioned stimulus combined with a gustatory antennal unconditioned stimulus. The drug was injected at different times before or after the learning session in order to dissociate its effects on acquisition, consolidation and retrieval processes. The performance was evaluated in short-delayed recall tasks. To control potential effects on sensory-motor activity, the effects of the drug were also investigated on sensory processes (through olfactory and gustatory functions) and on motor processes of proboscis extension. The results of conditioning experiments showed that pretrial injection induced a decrease of retention performance 1 h after the learning trial. Mecamylamine injected 20 min after the learning session induced a time-dependent impairment of retention performance, as has been shown by the performance level registered from 10 to 80 min after injection. A 5-min post-trial injection had no effect on retention performance. Control experiments did not reveal any effect of mecamylamine on the response reflex of proboscis extension and on responsiveness to olfactory stimuli (geraniol, lavender and vanillin). The absence of effects on sensory perception combined with the amnestic effect induced by pre- or late post-trial injections lead us to conclude that mecamylamine specially impaired acquisition and retrieval processes. The involvement of nicotinic-like receptors in these processes is discussed.

Animals↗
PubMed1995

Olfactory-visual associative learning in monkeys depends on intrahemispheric olfactory-visual interaction.

Three Cynomolgus monkeys (Macaca fasicularis) learned a series of food-visual conditional discrimination problems. In each problem, 1 of 2 possible food items was presented at the beginning of each trial and acted as an instruction cue as to which of 2 visually distinct stimulus objects the monkey must displace on that trial to obtain a further food reward. Following surgical disconnection of olfactory-visual intrahemispheric interaction, the monkeys were unable to use olfactory properties of the food items to guide visual choices. These results show both that olfactory differences between foodstuffs are a powerful olfactory stimulus, which can enter into cross-modal association with visual stimuli, and that this association depends on an intrahemispheric pathway of olfactory-visual interaction.

Afferent Pathways↗
PubMed2000

The cellular and molecular basis of odor adaptation.

An important recent advance in the understanding of odor adaptation has come from the discovery that complex mechanisms of odor adaptation already take place at the earliest stage of the olfactory system, in the olfactory cilia. At least two rapid forms and one persistent form of odor adaptation coexist in vertebrate olfactory receptor neurons. These three different adaptation phenomena can be dissected on the basis of their different onset and recovery time courses and their pharmacological properties, indicating that they are controlled, at least in part, by separate molecular mechanisms. Evidence is provided for the involvement of distinct molecular steps in these forms of odor adaptation, including Ca(2+) entry through cyclic nucleotide-gated (CNG) channels, Ca(2+)-dependent CNG channel modulation, Ca(2+)/calmodulin kinase II-dependent attenuation of adenylyl cyclase, and the activity of the carbon monoxide/cyclic GMP second messenger system. Identification of these molecular steps may help to elucidate how the olfactory system extracts temporal and intensity information and to which extent odor perception is influenced by the different mechanisms underlying adaptation.

Adaptation, Physiological↗
PubMed1995

Piriform cortex late activity revealed functional spatial heterogeneity.

Optical signals were recorded in the in vivo rat piriform cortex (PC) in response to olfactory bulb electrical stimulation. Sometimes the early response was followed by a longer latency component with an occurrence probability of 0.25. In order to compare the early and late activity, the ratio between early (disynaptic) and late wave amplitudes was measured at each recording site on the whole PC. Its spatial distribution revealed that the relative importance of the late activity was larger in the most posterior part of the PC whereas the late wave was rarely observed in the anterior PC. Such a result gave new information on the functional heterogeneity of the PC.

Animals↗
PubMed1982

Origins of anthropoid intelligence IV. Role of prefrontal system in delayed alternation and spatial reversal learning in a conservative eutherian (Paraechinus hypomelas).

A conservative eutherian mammal (the hedgehog, Paraechinus hypomelas) was tested on delayed alternation performance and spatial reversal learning before and after ablations of the prefrontal cortex. The anatomical results show that the cortical focus of the projections of the medial dorsal nucleus, the prefrontal cortex, does not include the neocortex on the dorsal convexity of the hedgehog's frontal lobe but, instead, the perirhinal and pregenual neocortex immediately surrounding the frontal convexity. The behavioral results show that normal performance of hedgehogs on these two behavioral tests depends upon the integrity of their prefrontal cortex, but not on the integrity of their frontal convexity or olfactory bulbs. The similarity in the results obtained from prefrontal hedgehogs and a divergent variety of other species with prefrontal ablations indicates that the role of the prefrontal system in the abilities measured by these two tests is at least as old as Eutheria and, thus, probably imposed persistent constraints on subsequent evolutionary modifications of the prefrontal system.

Animals↗
PubMed2002

[Magnetoencephalographic responses to odor and non-odor by fast Fourier transformation analysis in humans].

Magnetoencephalographic (MEG) responses to odor (amyl-acetate) and non-odor stimuli for 1 second were recorded in 9 healthy volunteers (right handed) with a dual 37-channel SQUID (Magnes, Bti Co.) and evaluated by fast Fourier transformation analysis, with the following results: 1. On MEG analysis, the spectral density increase in the left mid-central region at a frequency of 7 Hz was significantly greater in response to odor than in response to non-odor stimuli. This greater increase is apparently related to the presence of the odor perception mechanism in the orbital frontal area, a major center of the olfactory system. 2. Both increased and decreased spectral density areas at a frequency of 8 Hz were observed over the right hemisphere when no stimuli was compared with non-odor and no stimulus compared with odor. These changes may reflect a high level of vigilance caused by stimulation. 3. When no stimulus was compared with non-odor stimulation, a significant spectral density increase at a frequency of 11 Hz was noted. Similar trends were observed at frequencies of 11 and 12 Hz when no stimulus was compared with odor. These findings indicated increased attention in response to random presentation of odor and non-odor. 4. Significant differences at frequencies from 14 to 24 Hz were noted in the contralateral hemisphere when no stimulus was compared with odor stimuli. MEG spectral densities at 21 and 22 Hz were also noted in the contralateral hemisphere when no stimulus was compared with non-odor stimulus. These differences apparently arise from the response of the somato-sensory cortex to non-odor stimuli and amyl-acetate. Alternation of MEG spectral densities at frequencies from 14 to 17 Hz and 23 to 24 Hz in the left hemisphere was noted when no stimulus was compared with non-odor and no stimulus was compared with odor. These results appear to be related to "emotions" of pleasantness and unpleasantness evoked by non-odor and odor.

Adult↗
PubMedDate not supplied

[Behavior of cats after unilateral section of the brachii of the inferior colliculi].

In experiments on 13 cats a unilateral section of the brachii of inferior colliculi produced a stable interhemispheric asymmetry not only in the auditory system, but in other (vestibular, visual, somatic, olfactory) analysers as well, which led to a disturbance of adequate space perception. This was manifested in orienting reactions directed only to the side of brain lesion. Animals were no more able to distinguish between the right and left troughs either by spatial or by modal cues. A complete "disregard" by the animals of the trough contralateral to the side of lesion suggests a hemispheric lateralization of conditioned connections providing for an adequate direction of the animals' running.

Animals↗
PubMed2000

The role of the thalamic reticular neurons in alpha- and gamma-oscillations in neocortex: a mechanism for selective perception and stimulus binding.

The long-term objective is to understand how large masses of neurons in the brain process information during various learning and memory paradigms. Both time- and space-dependent processes have been identified in animals through computer-based analytic quantifications of event-related extracellular potentials. New nonlinear analyses have been introduced that presume that the fine-grain variation in the signal is determined and patterned in phase-space. Some neurons in the primary visual cortex manifest gamma-band oscillations. These cells show both a nonspecific phase-alignment (response synchrony) and a specific tuning (orientation tuning) when stimuli are presented to their receptive fields. This dual regulation of the sensory cells is proposed to underlie stimulus binding, a theoretical mechanism for "object" perception. Nonlinear analytic results from gamma-activities in a simple model neuropil (olfactory bulb) suggest that neuroplasticity may arise through self-organization, a process in which a nonlinear change in the dynamics of the oscillatory field potentials is the hallmark. This self-organization may follow simple dynamical laws in which global cooperativity among the neurons is transiently brought about that, over trials, results in enduring changes in the nonlinear dynamics of some neurons. In conclusion, the sculpturing of the synaptic throughput in the sensory cortex (stimulus binding) may be associated with the irregular phases of the gamma-activities and may result from both specific and nonspecific systems operating together in a nonlinear self-organizing manner.

Alpha Rhythm↗