Repeated subinflammatory ultraviolet B irradiation increases substance P and calcitonin gene-related peptide content and augments mustard oil-induced neurogenic inflammation in the skin of rats

The objective of the present study was to investigate interactions between odor hedonic tone, perceived odor intensity, olfactory judgments and stimulated nostril laterality. Subjects were stimulated in the right and the left nostril separately, with two odors: vanillin (pleasant); and indole (unpleasant). They had two tasks to perform: an intensity judgment; and an affective judgment. Two concentrations (one strong and one weak) of each odor were presented. Odors were presented for a short period corresponding to one inhalation (about 1 s). The inter-stimulus interval was always 30 s. The nostril stimulated and task presentation order were counterbalanced according to a Latin square. Odor presentation order was randomized for each subject. Results indicated that response times for unpleasant odors were significantly shorter than for pleasant odors during affective judgment and right nostril stimulation, indicating greater right hemisphere efficiency for the decoding of unpleasant affects induced by odors.     

The fish is bad: Negative food odors elicit faster and more accurate reactions than other odors

Dissociating between ‘good’ or ‘bad’ odors is arguable of crucial value for human survival, since unpleasant odors often signal danger. Therefore, negative odors demand a faster response in order to quickly avoid or move away from negative situations. We know from other sensory systems that this effect is most evident for stimuli from ecologically-relevant categories. In the olfactory system the classification of odors into the food or non-food category is of eminent importance. We therefore aimed to explore the link between odor processing speed and accuracy and odor edibility and valence by assessing response time and detection accuracy. We observed that reaction time and detection accuracy are influenced by both pleasantness and edibility. Specifically, we showed that an unpleasant food odor is detected faster and more accurately than odors of other categories. These results suggest that the olfactory system reacts faster and more accurately to ecologically-relevant stimuli that signal a potential danger.     

Startle reflex modulation during exposure to pleasant and unpleasant odors

The eyeblink component of the startle response to acoustic probes was measured while subjects smelled pleasant odors, unpleasant odors, or no odor. Peak electromyogram (EMG) 20–90 ms after probe onset was greater during unpleasant than during no odor conditions; EMGs for pleasant odors did not differ from those for no odor. Base tension in orbicularis oculi muscles was also higher during unpleasant odors. The results for unpleasant odors parallel those found in previous studies that have used a variety of methods for producing negatively valenced experiences. The results for pleasant odors diverge from those of most previous studies, which have found startle attenuation during positively valenced experiences. However, the results may be compatible with the suggestion (Lang, Bradley, & Cuthbert, 1992) that the motivational state that modulates startle involves both valence and arousal. Pleasant odors may require appropriate contexts to produce the positive motivational state required for startle attenuation.     

Discovering Alzheimer's disease and bipolar disorder white matter effects building computer aided diagnostic systems on brain diffusion tensor imaging features

Responses to affective stimuli are usually studied in just one sensory system at a time. However, this is rarely the way they are experienced. We were interested in how combining affective stimuli of similar intensities across two sensory modalities (smell and vision) would affect both behavioral responses (ratings) and psychophysiological responses (skin conductance). We studied this using olfactory stimuli delivered birhinally while the subjects viewed affectively laden scenes on a computer screen. Bilateral skin conductance recordings were taken throughout. Subjects rated the pleasantness of the images that they were viewing. We found a particularly salient effect of unpleasant smells, which enhanced the pleasantness ratings of certain images and also the skin conductance responses to unpleasant images.     

Identification of unpleasant odors is independent of age.

The purpose of this study was to investigate (a) the relationship between identification proficiency for specific odors and chronological age and (b) to determine whether the relationships were related to perceived quality (i.e., judgments of familiarity, intensity, and hedonics) of the odor item. Data from 472 subjects (227 men, 245 women) ranging in age from 18 to 79 years were assessed in a cued identification test comprising 16 odors. The results indicated a reliable age effect in overall odor identification performance. Further analyses indicated that the observed age-related deficit was odorant-specific, with some odors being equally well identified across age cohorts and others showing sensitivity to the process of aging. Additional examination regarding the observed age-differential effects across the different odor types indicated that these may be understood according to the pleasantness/upleasantness associated with the odor. Specifically, odors perceived as unpleasant showed age invariance whereas odors rated as pleasant exhibited age sensitivity.     

Probing affective pictures: Attended startle and tone probes

Reflexive eyeblinks to a startle probe vary with the pleasantness of affective pictures, whereas the corresponding P300 varies with emotional arousal. The impact of attention to the probe on these effects was examined by varying task and probe type. Probes were either nonstartling tones or startling noises presented during affective picture viewing. Half the participants performed a task requiring attention to the probes; the other participants were told to ignore the probes. Blinks to the startle probe varied with picture pleasantness for both task and nontask conditions. In contrast, P300 magnitudes for both startle and tone probes were reduced during emotionally arousing pictures, irrespective of pleasantness, in task and nontask conditions. Further, attending to the startle probe prompted an augmentation of N100 during unpleasant pictures. The data suggest that affective modulation of probe responses reflects obligatory processes in picture perception.     

Rapid mood change and human odors

We demonstrate an immediate effect of airborne chemicals on human moods. We collected six groups of underarm odors, respectively, from five prepubertal girls, five prepubertal boys, five college women, five college men, five older women, and five older men. In addition, we collected odors from homes of these donors, making them a seventh group of odor. Three hundred and eight odor observers ranked the seven groups of odors of little girls, little boys, college women, college men, older women, older men, and homes by their perceived pleasantness, intensity, perceived masculinity, and age of the donors, among other qualities. On a separate task, the same odor observers assessed their depressive, hostile, and positive moods twice, once before and once a few minutes after they sniffed one of the above seven groups of odors. Exposure to underarm odors for under 2 min led to significant, rapid, and small changes in the nonclinical depressive mood of the odor observers. The mood changes were independent of the observers' perceptions of odor qualities. Odors perceived as unpleasant and intense were as likely to relieve a depressive mood as were pleasant odors.     

Respiratory responses to olfactory stimuli in Parkinson's disease

There are many reports of olfactory impairment in patients with Parkinson's disease (PD) and the impairment can be observed before the appearance of typical PD symptom. Accordingly, olfactory screening tests may predict disease onset and indicates a need for early treatment before classic signs of the disease. Olfaction is dependent on inspiration, and activation of olfactory limbic areas are synchronized with the natural breathing cycle in animals and humans. Subconscious changes in respiratory pattern occur in response to odor stimulation. The use of olfactory stimuli to investigate respiratory pattern could be used to assess olfactory perception and serve as an index for olfactory limbic activation. In this study, we tested olfactory acuity in normal subjects and in patients with PD and recorded V(O2) and respiratory variables during pleasant and unpleasant odor presentation. All subjects were able to detect the odorants; however patients with PD were assigned to one of two groups, group that could recognize odors or the group with impaired odor recognition. Respiratory response toward unpleasant and pleasant odor recognition were weak in PD groups who could recognize odors than normal subject as well as emotional response to odor stimuli. PD group with impaired odor recognition showed no respiratory response toward odor stimuli. PD may experience difficulty in feeling positive emotions toward pleasant odors prior to the unpleasant odor because respiratory responses to pleasant odors may also be related to higher processes including intentional control of breathing pattern as a result of olfactory cortex processing and perceptions or emotions.     

Representations of odors in the rat orbitofrontal cortex change during and after learning

Cells in the orbitofrontal cortex (OF) respond to odors and their associated rewards. To determine how these responses are acquired and maintained, the authors recorded single OF units in rats performing an odor discrimination task. Approximately 64% of all cells differentiated between rewarded and nonrewarded odors. These odor valence responses changed during learning in 26% of all cells, and these changes were positively correlated with improving performance, supporting the idea that the information provided by these cells is used in learning the task. However, changes in odor valence responses were also observed after learning, and included not only increases in odor discrimination, but also decreases or mixed increases and decreases. Thus, only some of the changes in firing reflected acquisition of the task. The results suggest that learning triggers a continuing reorganization of OF neural ensembles representing odors and their rewards.     

Effects of pleasant and unpleasant ambient odors on human voice pitch

The perception of odors is well identified as having strong emotional correlates. It is also well known that the acoustic characteristics of the voice differ according to the emotional state. This study compared some acoustic features of the voice of 18 subjects reading the same text in pleasant (lavender) and unpleasant (pyridine) ambient odor conditions. The results revealed that the pitch of the voice was higher in the pleasant than in the unpleasant condition. These findings are consistent with the hypothesis of local and functional convergences of encoding vocal emotion and hedonic perception of odors.     

Remembering the past with slow breathing associated with activity in the parahippocampus and amygdala

Breathing plays an important role in perception of odors and the experience of emotions. We used the dipole tracing method to analyze brain areas related to odor-induced autobiographical memory and emotions estimated from averaged electroencephalograms triggered by inspiration onset during odor presentation. Odor stimuli were perfumes subjects named that elicited a specific, pleasant and personal memory as well as two pleasant odors for controls. The perfumes induced specific emotional responses during memory retrieval, arousal level of the memory, feelings of pleasantness and a sense of familiarity with the odor. Respiration measurement indicated that tidal volume increased and respiratory frequency decreased during presentation of perfume stimuli, showing a deep and slow breathing pattern. Throughout the olfactory stimulation, electroencephalograms and respiration were simultaneously recorded. In the averaged potentials, low frequency oscillation was phase-locked to inspiration. Dipole analysis showed that perfumes activated more widespread areas of the right parahippocampal cortex and converged in the right amygdala compared to control odors. Slow breathing synchronized with odor-induced autobiographical memory and emotions may be subconsciously stored in the parahippocampal cortex and amygdala.     

Ambient odors associated to failure influence cognitive performance in children.

We investigated whether odors can become conditioned to emotionally salient experiences such that when later encountered they influence performance consistent with a previously associated event. To test this hypothesis, 5-year-olds were given the experience of failure/frustration on a cognitive maze in a room scented with fragrance and later given another cognitively challenging test in a different room scented with either the same odor, a different odor, or no odor. Results revealed that subjects who performed the test in the presence of the same odor as the maze task did significantly worse than subjects in any other group. Performance in the different odor and the no odor groups were equivalent. Facial expressions and verbal remarks made during the maze task indicated a predominant display of negative affect. These findings show that odors can become conditioned to experiential states and when later encountered have directional influences on behavior.     

Effets du repas sur l''agrément d''odeurs alimentaires et nonalimentaires chez l''homme

Food-related and nonfood-related olfactory stimuli were presented to human subjects before and after they ate a meal. The subjects were asked to judge the pleasantness or the unpleasantness of the stimuli using a category scale. The responses of ten control subjects, who remained fasted, did not change during a 120 min period. With the other subjects on ad lib meals there followed these two characteristic phenomena: (1) there was a significant drop in the pleasantness of the food-related odors (negative alliesthesia); and, (2) there was no change in the pleasantness of the non-food-related odors (no alliesthesia). Therefore negative alliesthesia is specific to food-related odors. Negative alliesthesia reached a maximum within 60 min after the meals, then decreased and disappeared within the next 60 min. In three other subjects, with abnormal body weight, negative alliesthesia did not occur after the meal. These results favor the view that olfactory alliesthesia plays a role in satiety and the control of intermeal interval. They are also compatible with the existence of a ponderostat.     

Odors modulate pain perception: a gender-specific effect

Odors naturally provoke emotions that are pleasant or unpleasant. Prior studies have demonstrated the effects of pleasing odors on cognition and mood perception, but no studies have reported if they influence pain perception. In the present study, we measured the effect of, and relationship between, different odors on mood and experimental pain perception. Results show that odors significantly influence mood in both women and men. Compared to a neutral odor, pleasant odors produced a positive mood while unpleasant odors produced a negative mood. However, the effect of odor on pain was gender specific, as only women experienced the effects of odor on pain perception. Because no relationship was found between mood and pain perception, it could suggest that different mechanisms are involved in the emotional aspects of mood and pain perception. These results and their potential clinical implications are discussed.     

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.     

Olfactory influences on appetite and satiety in humans

Odor stimuli play a major role in perception of food flavor. Food-related odors have also been shown to increase rated appetite, and induce salivation and release of gastric acid and insulin. However, our ability to identify an odor as food-related, and our liking for food-related odors, are both learned responses. In conditioning studies, repeated experience of odors with sweet and sour tastes result in enhanced ratings of sensory quality of the paired taste for the odor on its own. More recent studies also report increased pleasantness ratings for odors paired with sucrose for participants who like sweet tastes, and conversely decreased liking and increased bitterness for quinine-paired odors. When odors were experienced in combination with sucrose when hungry, liking was not increased if tested sated, suggesting that expression of acquired liking for odors depends on current motivational state. Other studies report sensory-specific satiety is seen with food-related odors. Overall, these studies suggest that once an odor is experienced in a food-related context, that odor acquires the ability to modify both preparatory and satiety-related components of ingestion.     

Olfactory influences on appetite and satiety in humans

Odor stimuli play a major role in perception of food flavor. Food-related odors have also been shown to increase rated appetite, and induce salivation and release of gastric acid and insulin. However, our ability to identify an odor as food-related, and our liking for food-related odors, are both learned responses. In conditioning studies, repeated experience of odors with sweet and sour tastes result in enhanced ratings of sensory quality of the paired taste for the odor on its own. More recent studies also report increased pleasantness ratings for odors paired with sucrose for participants who like sweet tastes, and conversely decreased liking and increased bitterness for quinine-paired odors. When odors were experienced in combination with sucrose when hungry, liking was not increased if tested sated, suggesting that expression of acquired liking for odors depends on current motivational state. Other studies report sensory-specific satiety is seen with food-related odors. Overall, these studies suggest that once an odor is experienced in a food-related context, that odor acquires the ability to modify both preparatory and satiety-related components of ingestion.     

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.     

Enrichment to odors improves olfactory discrimination in adult rats

The authors tested how prior odor enrichment affects the spontaneous discrimination of both preexposed and novel odors. Experimental rats were exposed to single odors or to pairs of similar or dissimilar odors for 1-hr periods twice daily over 20 days. Spontaneous discriminations between pairs of similar odors were tested before and after the odor exposure period using an olfactory habituation task. The authors found that (a) experimental rats did not spontaneously discriminate similar odor pairs before the exposure period, whereas they spontaneously discriminated them after the enrichment period, and (b) the improvement of performance was not selective for the odors used during enrichment. These results show that odor experience changes perception in the manner predicted based on other groups' electrophysiological experiments.     

The use of an unpleasant sound unconditional stimulus in an aversive conditioning procedure with 8- to 11-year-old children

The study of aversive Pavlovian conditioning in children can contribute to our understanding of how fears are acquired and extinguished during development. However, methodological issues hamper further research because of ethical and procedural concerns regarding the use of traditional aversive unconditional stimuli (USs) and no established method to measure trial-by-trial changes in the child's expectancy of the US. The present experiment used geometric shape conditional stimuli (CSs) and an unpleasant sound US with 8- to 11-year-old children. Reliable acquisition and extinction were observed with first, second, and third interval skin conductance responses, on-line expectancy judgments, and post-conditioning subjective ratings of pleasantness and arousal. The experiment confirms the novel use of an unpleasant sound of metal scraping on slate as a US in aversive conditioning with children. The methods have the potential to facilitate the ethical conduct of aversive conditioning research in children using psychophysiological, affective, and self-report expectancy measures.