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.     

The capacity of humans to identify odors in mixtures

One hundred and twenty-three subjects were given the task of identifying the constituents of stimuli consisting of 1-5 odorants. The highest level of identification occurred with single odors and few subjects correctly identified the constituents of mixtures. Since the stimuli were common, dissimilar odors, the results suggest that the capacity of humans to process information about odors perceived simultaneously may be limited, or that odors in mixtures blend to form a new odor with few of the characteristics of the constituent odors.     

Smart orthosis for the treatment of adolescent idiopathic scoliosis

There is considerable controversy regarding the effectiveness of orthotic treatment for patients with adolescent idiopathic scoliosis. Most researchers believe that, to be effective, the orthosis must be worn as prescribed for both compliance and tightness. Compliance is the time the brace is worn relative to the prescribed time. A battery-powered microcomputer system was developed to monitor and maintain the loads exerted by orthoses used to treat children with spinal deformities during daily living. This system not only records how well and for how much time the brace has been used, but also helps patients to ensure that the brace is being worn at the prescribed tightness. Laboratory tests were performed, and five patients used the system for four weeks. The patients reported that the system helped them to wear the orthoses correctly and comfortably. The time that the patients wore the orthoses at the prescribed tightness level increased from 53±9% during the monitoring period (first 2 weeks) to 68±14% during the automatic adjustment period (last 2 weeks).     

An assessment of the salient olfactory environment of formula-fed infants.

Olfactory preferences of two-week-old bottle-fed infants were assessed in a series of simultaneous two-choice tests. Infants of each sex displayed preferential orientation to a stimulus pad worn on their mother's breast over a clean control pad. When maternal breast odor was paired with the odor of the infants' formula, however, boys spent more time oriented toward the formula odor, whereas girls evinced no reliable preferences. Although the subject infants had no prior direct contact with odors emanating from the breasts of lactating females, but had recurring reinforced exposure to the odor of their familiar formula (in the context of feeding), the former scents elicited a more positive response. Preferential orientation to lactating-breast odors reflects adaptive inborn attraction to cues associated with the natural food source for human neonates.     

Source and Item Memory for Odors and Objects in Children and Young Adults

Recall and recognition memory for odors are poorer in children than in adolescents. In addition, children perform worse than young adults on source memory tasks using visual and auditory stimuli. However, source memory for odor stimuli has not been examined in children. This study investigated source and item memory for odors and objects in children (7–10 years old) and young adults (18–24 years old). During the study phase, 1 male and 1 female experimenter (sources) randomly presented either 16 odors or 16 objects to the participant. Presentation alternated between sources so that each source presented 8 stimuli. Once the 16 stimuli were presented, the sources exited and a third experimenter began the test phase. To assess item recognition memory, a stimulus from the study phase and a novel stimulus were presented to the participant who was asked to choose the stimulus presented during the study phase. Source memory was assessed with the 8 stimuli from the study phase not used in the item memory task. The experimenter presented a stimulus and asked whether the male or female experimenter had presented the stimulus during the study phase. Results indicate that difference scores between item and source memory for odors were significantly larger for children than for young adults, indicating poorer source memory for children than adults. Difference scores for objects did not distinguish between groups. It has been suggested that the frontal lobes play a critical role in source memory and odor memory—a brain region that continues to develop into adolescence. Poor performance among children on the source memory task for odors may be due in part to immaturity of the frontal lobes.     

Source and item memory for odors and objects in children and young adults

Recall and recognition memory for odors are poorer in children than in adolescents. In addition, children perform worse than young adults on source memory tasks using visual and auditory stimuli. However, source memory for odor stimuli has not been examined in children. This study investigated source and item memory for odors and objects in children (7-10 years old) and young adults (18-24 years old). During the study phase, 1 male and 1 female experimenter (sources) randomly presented either 16 odors or 16 objects to the participant. Presentation alternated between sources so that each source presented 8 stimuli. Once the 16 stimuli were presented, the sources exited and a third experimenter began the test phase. To assess item recognition memory, a stimulus from the study phase and a novel stimulus were presented to the participant who was asked to choose the stimulus presented during the study phase. Source memory was assessed with the 8 stimuli from the study phase not used in the item memory task. The experimenter presented a stimulus and asked whether the male or female experimenter had presented the stimulus during the study phase. Results indicate that difference scores between item and source memory for odors were significantly larger for children than for young adults, indicating poorer source memory for children than adults. Difference scores for objects did not distinguish between groups. It has been suggested that the frontal lobes play a critical role in source memory and odor memory—a brain region that continues to develop into adolescence. Poor performance among children on the source memory task for odors may be due in part to immaturity of the frontal lobes.     

The human brain representation of odor identification

Odor identification (OI) tests are increasingly used clinically as biomarkers for Alzheimer's disease and schizophrenia. The aim of this study was to directly compare the neuronal correlates to identified odors vs. nonidentified odors. Seventeen females with normal olfactory function underwent a functional magnetic resonance imaging (fMRI) experiment with postscanning assessment of spontaneous uncued OI. An event-related analysis was performed to compare within-subject activity to spontaneously identified vs. nonidentified odors at the whole brain level, and in anatomic and functional regions of interest (ROIs) in the medial temporal lobe (MTL). Parameter estimate values and blood oxygenated level-dependent (BOLD) signal curves for correctly identified and nonidentified odors were derived from functional ROIs in hippocampus, entorhinal, piriform, and orbitofrontal cortices. Number of activated voxels and max parameter estimate values were obtained from anatomic ROIs in the hippocampus and the entorhinal cortex. At the whole brain level the correct OI gave rise to increased activity in the left entorhinal cortex and secondary olfactory structures, including the orbitofrontal cortex. Increased activation was also observed in fusiform, primary visual, and auditory cortices, inferior frontal plus inferior temporal gyri. The anatomic MTL ROI analysis showed increased activation in the left entorhinal cortex, right hippocampus, and posterior parahippocampal gyri in correct OI. In the entorhinal cortex and hippocampus the BOLD signal increased specifically in response to identified odors and decreased for nonidentified odors. In orbitofrontal and piriform cortices both identified and nonidentified odors gave rise to an increased BOLD signal, but the response to identified odors was significantly greater than that for nonidentified odors. These results support a specific role for entorhinal cortex and hippocampus in OI, whereas piriform and orbitofrontal cortices are active in both smelling and OI. Moreover, episodic as well as semantic memory systems appeared to support OI.     

Relation of olfactory EEG to behavior: factor analysis

Rabbits were conditioned to lick (CR+) in response to one odor (CS+); another odor (CS-) served as a discriminative control (CR-). Electroencephalograms (EEGs) were recorded from arrays of 64 electrodes on the olfactory bulb in three stages, each with six sessions: in Stage I, odors A+ and B-; in Stage II, odors C+ and B-; and in Stage III, odors C+ and A-. Spatial EEG amplitude patterns were measured for multiple control (C), CS+, and CS- EEG bursts in each trial. Data were transformed via factor analysis and expressed by factor scores as spatial patterns specified by factor loadings. In discriminant analysis of the factor scores, we correctly classified the C and CS bursts on the average by 65-80% from all trials for each subject and session and by 75-90% for trials with correct CRs. The latter was confirmed with a stepwise linear discriminant analysis of the original 64-variable data. Factor patterns were relatively invariant within but changed between stages. The results implied that stable spatial patterns of bulbar activity emerged in respect to CSs under reinforcement and persisted until the stimulus-response contingencies were changed.     

Fear, risk assessment, and playfulness in the juvenile rat

The effects of predatory odors on play were assessed in juvenile rats. When rats were exposed directly to a collar previously worn by a cat, play was abolished and remained suppressed for up to 6 days. Providing rats with an opportunity to hide did not alter cat odor's ability to reduce their play. Rat play was also suppressed shortly after they were exposed to cat odor in their home cage, and a substantial amount of risk assessment behavior was present up to 24 hr later. Trimethylthiazoline, a component found in fox feces, only reduced play during exposure. These data suggest that predatory odor-induced reductions in play may provide a useful model for gaining insight into the consequences of fear and anxiety in young animals.     

Studying the effects of smell and taste experience in the pediatric population using functional near infrared spectroscopy: A hypothesis

There are different postnatal sensitive periods throughout the development course of sensory functions. During sensitive periods, there is a biological display of an extreme neural sensitivity to the storage of experience-driven sensory information that is not present outside these developmental stages. This neural property is reflected in subjects’ reported preferences for sensory stimuli, such as odors and tastes. The human brain mapping approach (HBA) has demonstrated that disease-free human postnatal and later development of any sensory function parallels morphological and functional development of the CNS and that this development correlates with signal changes that have been acquired by means of neuroimaging techniques. Whether experience with tastes and/or odors has a stronger effect on the perception of gustatory and/or olfactory stimuli the earlier subjects are exposed to certain odors and tastes is still unknown. It is also unknown, whether as well as how this effect is reflected in brain activation patterns and whether we are currently able to identify sensitive periods of gustatory and olfactory development from the imaging signals. To answer these research questions, repeated exposure to tastes and/or odors should be applied in children of different age ranges in order to induce different age-related degrees of olfactory/gustatory preferences as well as different aged-related patterns of oxyhemoglobin (OH) and deoxyhemoglobin (DOH) changes that should be measured by means of the functional near-infrared spectroscopy (fNIRS) technique.     

Allergic reactions associated with airborne fish particles in IgE-mediated fish hypersensitive patients

We evaluated the clinical characteristics found in 21 children who showed allergic reactions upon incidental inhalation offish odors or fumes, from 197 diagnosed with IgE-mediated fish hypersensitivity. Allergic reactions to fish via ingestion began in most patients (86%) within the first 24 months of life. The vast majority (19/21) of patients showed cutaneous symptoms, either alone or, less frequently, associated with other clinical manifestations. Hake and flounder were the species offish most frequently implicated in eliciting clinical manifestations upon ingestion. After diagnosis, all these patients were placed on a strict fish-avoidance diet. During this period of avoidance, patients reported allergic reactions (mean age 7 years) after incidental exposure to airborne fish odors or fumes. Clinical manifestations through inhalation were respiratory (mainly wheezing) in 12 patients and cutaneous (mainly urticaria) in nine patients. Nineteen of 21 patients reported three or more episodes upon exposure to fish aerosols; in most cases, these episodes occurred at home when other people were eating fish. In conclusion, incidental inhalation of fish odors or fumes could play an important role in accidental and unknown encounters with fish in children on fish-avoidance diets for fish IgE-mediated hypersensitivity. Such exposures could elicit clinical symptoms and could have some effect in delaying the development of tolerance.     

Selective depletion of bacteria alters but does not eliminate odors of individuality in Rattus norvegicus

To determine if odors of individuality are influenced by the removal of Gram-negative or Gram-positive gut bacteria, Long-Evans rats were trained in an operant olfactometer to discriminate between the odors of two individual conspecifics and their operant responses to three different odors in randomly presented probe trials were analyzed. Significantly more responses were made to the probe odors from two known individuals than to the probe odors from known individuals with their Gram-negative bacteria eliminated (Experiment 1) or their Gram-positive bacteria eliminated (Experiment 2). Responses to the probe odors from known rats with bacterial selectively depleted did not differ significantly from responses to probe odors from unknown rats. These results support the hypothesis that the urinary odor of an individual rat is altered by the removal of specific gut bacteria. In Experiments 3 and 4, subjects made fewer errors in learning to discriminate between the odors of the familiar rats whose bacteria had been selectively depleted than between the odors of unknown rats. This "savings effect" indicates that some components of the individual urinary odors were retained after the removal of specific gut bacteria. Thus, the eliminated bacteria were not totally responsible for the odors of individuality. The outcome of Experiments 3 and 4 also indicates that conclusions regarding the recognition of odors by rats should not be made on the outcome of probe trial experiments alone.     

Maternal and paternal pheromones in gerbils

Mongolian gerbil pups are attracted to maternal and parental nest odors. They approach these odors in preference to the odors of either virgin females or clean bedding. The pups do not distinguish between maternal or parental odors and odors of unfamiliar lactating females. Thus lactating female gerbils produce a maternal pheromone similar to that of rats and other rodents. Attraction to the pheromone develops by two weeks of age and persists for at least three weeks. The primary source of the pheromone is the mother's enlarged ventral scent gland. Removing this gland eliminates maternal attractiveness. Development of attraction to maternal scent gland odors depends on prior exposure to them. Pups raised by mothers lacking scent glands do not approach lactating females that have scent glands. The father's presence during development alters the responses of gerbil pups to odors of other males. Pups raised by both parents avoid odors of other pairs with young, whereas pups raised by their mothers only do not. Pups are not attracted to their father's odors.     

Attraction of gerbil pups to maternal nest odors: Duration,specificity and ovarian control

Gerbil pups are attracted to the odors of their maternal nest. This attraction develops by three weeks and is still strong at six weeks, but ceases by nine weeks of age. Removing either the mother's scent gland or her ovaries, a procedure that decreases scent gland size, decreases pup attraction to maternal nest odors. These data suggest that the mother's scent gland is the primary, though not the sole, source of the maternal nest attractants and that ovarian steroids stimulate attractant production. The gradual decline in pup attraction to maternal nest odors with age also parallels the decrease in maternal scent gland size. Pup attraction to nest odors becomes more specific as pups mature. Based on pup responses to odors of other mothers and their young, we suggest that nursing pups approach a species-typical pheromone produced by all lactating females, but that weaning pups imprint on scent gland odors specific to their mother. Other maternal odors and/or odors produced by the pups may also make the nest attractive to the young.     

Discrimination of odors from stressed rats by non-stressed rats

Comparison of earlier reports of rat stress odors is complicated by the many differences in experimental parameters and responses measured. To evaluate whether these stress odors provide a special signal, rats were subjected to different levels of stressful foot-shock in one half of a simple two-compartment test box whilst the other half was clean and unoccupied. The results show that whilst test subjects preferred the half containing odors from non-stressed rats, this preference was decreased by the presence of stress odors to an extent concordant with the level of stressor applied to the odor donors. There were no differences in plasma corticosterone among the odor donors indicating that this hormone is probably not the source of stress odors. Plasma corticosterone levels of the subjects were similar to each other and to the odor donors. Compared to odors from non-stressed rats, stress odors increased the activity of the subjects. The evidence strongly suggests a special signalling function for stress odors although responses to this signal are not stereotyped.     

Volatile female odors activate the accessory olfactory system of male mice without physical contact

We previously reported that male mice are more attracted to volatile odors from intact female mice than from ovariectomized female mice. In the present study, we investigated male attraction to volatile odors from soiled bedding collected from the cages of estrous or ovariectomized female mice. There was no difference in the total time spent sniffing volatile odors from estrous and ovariectomized female mice, suggesting that female mice emit volatile odors which are not excreted into bedding. To test this possibility, we investigated c-Fos expression in the mitral cell layer and granule cell layer of the accessory olfactory bulb 60 min after exposure of male mice to volatile odors without physical contact. Volatile odors from an estrous female mouse significantly increased the total number of c-Fos positive cells in each of the rostral and caudal granule cell layer, but not in the mitral cell layer. After exposure to volatile odors from estrous bedding, the total number of c-Fos positive cells did not increase. Volatile odors from a male mouse did not increase the total number of c-Fos positive cells. Volatile odors from an ovariectomized female mouse increased c-Fos expression only in the caudal granule cell layer. These results suggest that female mice emit specific volatile odors which are not excreted into bedding, and that the volatile odors activate the accessory olfactory system of male mice without physical contact. To characterize the female-specific volatile odors, we conducted habituation-dishabituation tests. Whereas sham-operated male mice discriminated between volatile odors of estrous and ovariectomized female mice, vomeronasal organ-removed male mice did not. These results suggest that male mice discriminated whether or not female mice were ovariectomized, by volatile odors via the accessory olfactory system, and that the female-specific volatile odors are involved in reproduction.     

Perception of odor quality by Free Image-Association Test]

A method was devised for evaluating odor quality. Subjects were requested to freely describe the images elicited by smelling odors. This test was named the "Free Image-Association Test (FIT)". The test was applied for 20 flavors of various foods, five odors from the standards of T&T olfactometer (Japanese standard olfactory test), butter of yak milk, and incense from Lamaism temples. The words for expressing imagery were analyzed by multidimensional scaling and cluster analysis. Seven clusters of odors were obtained. The feature of these clusters were quite similar to that of primary odors which have been suggested by previous studies. However, the clustering of odors can not be explained on the basis of the primary-odor theory, but the information processing theory originally proposed by Miller (1956). These results support the usefulness of the Free Image-Association Test for investigating odor perception based on the images associated with odors.     

Rat's responses to blood and body odors of stressed and non-stressed conspecifics

Male rats were tested in a Y-maze for exploratory responses to odors from stressed and non-stressed rats, and from the blood of stressed and non-stressed rats. Significant differences in activity but not preference were obtained in rats receiving odors from stressed and non-stressed rats. Odors from rats given 5 random, signalled, 2 sec electric shocks over 15 min, significantly increased the activity of receivers, compared to responses elicited by odors from non-stressed animals (Experiment 1). Odors from rats given 12 random, signalled, 2 sec electric shocks over 35 min significantly reduced receivers' activity (Experiment 2). Interestingly, responses of rats to odors from the blood of stressed and non-stressed rats were similar to their responses to odors from stressed and non-stressed rats. It is concluded that responses to these odors depend upon the stressor applied to the odor producing rats. Rats subjected to different stress conditions may change the quality or concentration of the odors they emit and thereby alter the responses of rats receiving the odors.     

The sources of odors from stressed rats

Recent studies [8,9] have shown that odors from stressed Norway rats act as signals to which other rats respond primarily by overall changes in activity and exploration. At present the source of these odors is unknown. In this study odors from urine, feces and the bodies of stressed rats were delivered along a runway in which the subjects had been previously trained to run for a water reward in the presence of odors from non-stressed rats. The results indicate that odors are released from the body surface and in the urine but not the feces of stressed rats.     

Olfactory experience and the development of odor preference and vaginal marking in female Syrian hamsters

Rodent reproductive behavior relies heavily on odor processing, and evidence suggests that many odor-guided sexual behaviors are shaped by prior experience. We sought to determine if exposure to male odors during development is required for the adult expression of proceptive sexual behavior toward male odors in female Syrian hamsters. Exposure to male odors was restricted in na?ve subjects by removing all male siblings from the litter at three to five days of age. Control litters were also culled, but included equal numbers of male and female pups. As adults, na?ve females displayed investigatory preferences toward male odors in a Y-maze that were comparable to control females; this preference was observed whether contact with the odor stimuli was prevented of allowed. In contrast, na?ve females vaginal scent-marked equally toward male and female volatile odors, suggesting an inability to target behavior toward sexually relevant odors. However, na?ve females marked preferentially toward male odors when allowed to contact the odor stimuli. These results provide evidence for the experience-dependent development of vaginal marking behavior toward volatile components of sexual odors. Furthermore, they suggest that distinct mechanisms regulate the development of odor preferences and vaginal marking behavior in this species.