The present study included a large variability in scores across the ASC group, and the scores overlapped with those of the control group. While research has shown that olfactory sensitivity is quite common and is evident in over half of people with ASC , it also indicates that differences in olfactory functioning are not apparent in all people with ASC. This variability suggests other factors could interact with the olfactory system and play a role in the degree of sensory sensitivity in ASC. One potential factor that could be important for olfactory processing is the perceived pleasantness of the odour stimuli for people with ASC . Research has found that the degree of pleasantness rated for different odours in ASC was related to how easily they identified odours, with more pleasantly-rated odours being easier to iden- tify, and more unpleasant odours identified with greater difficulty . Therefore, it is possible the pleasantness level of odours for people with ASC could also affect their detection threshold for that odour. The partici- pants in the present study did not rate the pleasantness of the odour stimuli used in the task, so its role in the results cannot be determined. People with ASC also show differences in neural habituation to repeated stim- uli, generally showing reduced habituation compared to controls [53,54]. There is also evidence that reduced habituation in ASC affects sensory processing and may play a role in atypical sensory sensitivity . However, the present findings within olfaction do not support the idea that differences in habituation were involved in the results, as there was no evidence for differences in habituation or learning effects across the trials for those with ASC.
Within the Perciformes, the largest teleost order (Order Summary for Perciformes, www.fishbase.org), studies on olfactory sensitivity to, and pheromonal function of, hormonal steroids are scarce and derive from a few representatives of the Gobiidae (Colombo et al., 1980; Corkum et al., 2008; Murphy et al., 2001; Tierney et al., 2013) and Cichlidae (Cole and Stacey, 2006; Hubbard et al., 2014; Keller- Costa et al., 2014). Cichlids are an extremely diverse taxon with currently 1670 described species (‘List of Nominal Species of Cichlidae’, www.fishbase.org), mostly native to Africa, and adaptation of the sensory and signalling systems to different environmental conditions has been suggested as an important driver in African cichlid radiation (Seehausen et al., 2008). Focus so far has mainly been on the evolution of colour polymorphism that is linked to light heterogeneity in the habitat (Seehausen et al., 2008) alongside specialisation for particular trophic niches (Greenwood, 1991). Divergent selection on chemical communication systems may, however, constitute an additional speciation factor. Nevertheless,
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C. auratus typically inhabits land-locked still waters or the slow-moving lower reaches of rivers. It is possible, therefore, that it might, on occasion, come into contact with dilute sea water (e.g. in the upper reaches of estuaries) but the main source of variation in the calcium content of its environment is likely to be the source of the water (i.e. the underlying geology) or, possibly, human activity (Douglas et al., 1996). We hypothesise that any olfactory sensitivity to calcium might therefore be involved in activation and/or regulation of the appropriate physiological responses to elevations or decreases in environmental Ca 2+ , rather than solely the recognition of
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Abstract: The ability to smell is crucial for most species as it enables the detection of environmental threats like smoke, fosters social interactions, and contributes to the sensory evaluation of food and eating behavior. The high prevalence of smell disturbances throughout the life span calls for a continuous effort to improve tools for quick and reliable assessment of olfactory function. Odor-dispensing pens, called Sniffin’ Sticks, are an established method to deliver olfactory stimuli during diagnostic evaluation. We tested the suitability of a Bayesian adaptive algorithm (QUEST) to estimate olfactory sensitivity using Sniffin’ Sticks by comparing QUEST sensitivity thresholds with those obtained using a procedure based on an established standard staircase protocol. Thresholds were measured twice with both procedures in two sessions (Test and Retest). Overall, both procedures exhibited considerable overlap with QUEST displaying slightly higher test-retest correlations, less variability between measurements, and reduced testing duration. Notably, participants were more frequently presented with the highest concentration during the QUEST which may foster adaptation and habituation effects. We conclude that further research is required to better understand and optimize the procedure for assessment of olfactory performance.
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In conclusion, the results of the present study provide further evidence of a well-developed olfactory sensitivity in two non- human primate species, the squirrel monkey and the pigtail macaque. These findings support the idea that olfaction may play an important role in the regulation of behaviour in these species. Further, they suggest that across-species comparisons of neuroanatomical features are a poor predictor of olfactory performance and that general labels such as ‘microsmat’ and ‘macrosmat’ are inadequate to describe a species’ olfactory capabilities. An ecological view of such capabilities that attempts to correlate sensory performance with the behavioural relevance of odour stimuli might offer a promising approach in appraising the significance of the sense of smell for a particular species.
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determine this. Although we only managed to collect one sample, the fact that the ovarian fluid proved to be less potent than urine, and the olfactory response depended on neither the sex nor maturity of the receiver is, perhaps, counter-intuitive. However, although salmonids have been shown to have a similar olfactory sensitivity to ‘ urogenital fluid ’ (assumed to be mostly ovarian fluid; Kitamura and Ogata, 1989), it does not have the same attraction to males as urine from mature females (Olsén et al., 2002), although it may have some attractive properties (Emanuel and Dodson, 1979). Sole spawn in pairs (Baynes et al., 1994; Carazo et al., 2016) with little opportunity for other males or females to participate once the swimming assent has started to liberate gametes and this may be related to the lack of involvement of ovarian fluid in communication. Together, these findings suggest that ovarian fluid is less important than urine in chemical communication in sole, although it may enhance sperm motility (Carazo et al., 2016; Diogo et al., 2010) as in other teleosts (for example, see Elofsson et al., 2006; Rosengrave et al., 2009). Mucus, a highly potent odorant in the European eel (Huertas et al., 2007), was without significant olfactory potency in the sole so may not be important in chemical communication, even though males and females may be in close contact during courtship (Carazo et al., 2016). Urine source
All three species of primate tested here have been reported to display anogenital sniffing (Hopf, 1974; Klein, 1971; Reite and Short, 1980) and thus exposure to conspecific faecal odours that may convey behaviourally relevant information. However, in this context, too, there is too little quantitative information available with regard to both the frequency of such behaviours and possible differences in the composition of faecal odours among the three primate species to draw conclusions that might explain the observed odorant-specific differences in sensitivity. Future studies should therefore aim at analysing the chemical environment of non-human primate species, with particular emphasis on differences in the frequency of occurrence of odorants presumed to play a role in controlling their behaviour. A second aspect of the present study is our finding of a significant correlation between olfactory detection thresholds and carbon chain length of the thiols in the spider monkeys and the squirrel monkeys (see Fig.·5), and a marked effect of the presence vs absence of a methyl group on the detectability of indols in the squirrel monkeys and pigtail macaques (see Fig.·6). Corresponding correlations between olfactory sensitivity and length of the carbon chain backbone have also been found in all three species of non-human primate as well as in human subjects for homologous series of esters, alcohols, aldehydes, ketones
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concentration from 10 mmol l −1 (open horizontal bars) to 0, 2 and 6 mmol l −1 (shaded horizontal bars) flowing over the olfactory epithelium. All three traces were recorded from the same fish. The vertical scale bar refers to the nerve traces only, but the horizontal scale bar refers to both nerve and integrated traces; all integrated traces are shown at the same gain. Note that the amplitude of the integrated response is large and shows no accommodation within the time scale of the stimulus (10 s). (B) Semi-logarithmic plot of pooled data (N=6) showing the concentration dependency of the olfactory response to changes in [Ca 2+ ]
have suggested that the olfactory system plays a role as a sentinel system rather than a ﬁne-tuned selection system . As such, its central function would be to produce emotional responses to odors that would serve as the base for approach- avoidance behaviors . Labroo and Nielsen (2010) suggested that people can subconsciously reverse the approach-avoidance relationship , describing the possibility of reducing aversion to certain immediately aversive items that may be beneficial to health. Internal mechanisms have evolved in both humans and animals, enabling them to maximize their chances of survival when encountering threats, by responding to adverse information that indicates risk and very quickly determining whether the environmental stimulus is dangerous or not. Conversely, weakening the intensity value of the pleasantness of the rose odorant reflects the potential necessity to heighten rose odorant application in the high DQ frequency group. It remains to be elucidated if this functional resilience results in improved adaptive responses for dysmenorrhea women.
One clade of mammals that exhibits substantial variation in the extent of the olfactory recess is the New World leaf-nosed bats (Family Phyllostomidae). One way to quantify this difference is to calculate the percentage of olfactory epithelium contained within the olfactory recess. This parameter relates to the size of the olfactory recess because, in all species examined, virtually all of the olfactory recess is lined with olfactory epithelium. We have found that some species have less than 10% of their total olfactory epithelium located within the olfactory recess, while other species have a third or more of their olfactory epithelium located within the olfactory recess (Eiting et al., in press). In this study, we examine the hypothesis that an enlarged olfactory recess improves olfactory airflow in phyllostomid bats. To examine this hypothesis, we generated a steady-state model of airflow through the nasal passage of the short- tailed fruit bat, Carollia perspicillata (Linnaeus), and compared it with airflow predicted from models in which we artificially reduced and enlarged the olfactory recess. This species is common throughout much of the New World tropics, and it is often used in experimental and behavioral work, including previous work on olfactory sensitivity and discrimination (Laska, 1990a; Laska, 1990b; Thies et al., 1998). Carollia perspicillata lies near the base of the radiation of frugivores within the phyllostomids, and it is morphologically intermediate between the long-nosed nectar-feeding bats and the short-nosed canopy frugivores (Dumont et al., 2012; Freeman, 1988; Freeman, 2000). These two features make this species a well-suited model to study olfactory airflow.
Chemoreception is an important sensory me- chanism in fish, which helps to recognise prey or potential mates and favourable habitat within the aquatic environment . The olfactory apparatus of fish can perceive chemical odorants from the aquatic environment through the nostrils . The external variation of the snout, nostrils and olfactory appa- ratus in P. lanceolatus, L. guntea and M. armatus are demarcated in different aspects, viz. distance between the nostrils, number of olfactory lamellae, occurrence of accessory nasal sacs, length of the ol- factory nerve tracts, neuroepithelial folding, etc. The morphometry of the snout in fish may be related to the ecological niche based on the feeding behaviour of the respective species . Variation in snout morphology may denote the diversity of foraging pattern as well as habitat preference of the species . The external structures of snout in P. lanceo- latus, L. guntea and M. armatus are also variable, what may indicate differences in ecological habitat and feeding habits. The olfactory apparatus of fish is present at the snout region of the head. Anato- mical difference in this chemosensory apparatus is not correlated with the variable olfactory sensitivity in the species . This phenomenon may be inter- preted as the species-specific variation between the experimental specimens. The olfactory sensitivity is directly related to the physical interaction of the sensory receptor cells and chemical odorants during water ventilation over the olfactory neuroepithelium . The occurrence of the olfactory neuroepithelial cells (viz. sensory receptor cell, supporting cell and basal cell) is very similar amongst the experimental specimens and probably plays a vital role in olfac- tory sensitivity in fish [5, 8]. However, the increased lamellar surface of the olfactory neuroepithelium is caused by the frequent neuroepithelial folding to form olfactory rosette . Number of the olfactory lamellae within the olfactory rosette of L. guntea and M. armatus represents the interspecific variation. Flat olfactory neuroepithelium of P. lanceolatus may
Olfactory function was assessed using the Sniffin’ Sticks Extended Test [25,26], an olfactory test commercially dis- tributed by Burghart, Medizintechnik, GmbH ( Wedel , Germany ). It consists of three different sub-tests, assessing the olfactory sensitivity (threshold), discrimination and identification, typical tasks of the olfactory system. In this version of the test, the olfactory sensitivity to n-butanol was employed. The olfactory threshold is considered as the minimum concentration of an odorant (n-butanol) that can be detected by a subject. N-butanol was pre- sented in 16 different dilutions in felt tip pens. For each trial the blindfolded subject was subjected to three differ- ent stimuli, one consisting of a given concentration of n- butanol, and the other two with blank stimuli. The subject was asked which of the three stimuli contained the n- butanol (or, equivalently, which of the three stimuli was the strongest). Depending upon the correct and wrong an- swers given, the concentration of the stimulus was changed and the trial was repeated up to seven staircase reversals. The threshold score was calculated by per- forming a mean of the values of four last reversals. The ol- factory discrimination’s aim was to assess the subject’s ability to discriminate between different odorants. Even in this case the subject was blindfolded and 16 different trip- lets of odorants were presented. For each triplet, two felt tip pens contained the same odorant, while the third one held a different substance. The subject was asked which of the three pens contained the different odorant. The olfac- tory identification test aimed to evaluate the subject’s abil- ity to correctly identify an odorant. The subject was presented with16 different odorants and asked to identify them by choosing between four possible odors for each trial. In this final test, the subject was not blindfolded. Each of these tests yielded a score, and the total sum of the three sub-scores was called “TDI (Threshold Discrim- ination Identification) Score”, relating to olfactory func- tion. We chose to employ a bilateral testing, in order to avoid possible false results due to the congestion of one of the two nostrils, even though the presence of flu and/or nasal problems was included in the exclusion criteria of the survey. The test was performed once for each partici- pant, given the high test-retest reliability of the method employed (r = 0.80 for Odor Discrimination, r = 0.88 for Odor Identification, r = 0.92 for Odor Threshold) [25,27]. The reliability data obtained in previous pilot studies are in agreement with data above mentioned.
In order to increase knowledge concerning the response to DMS and to provide experimental support for generalizations of DMS- driven foraging behaviour, we investigated the response of Cory’s and Scopoli’s shearwaters to this compound, in relation to different environmental and ecological settings in the northern hemisphere. These are two closely related medium-sized petrel species that breed in the northern hemisphere waters during summer and migrate south for wintering (Dias et al., 2011; Ristow et al., 2000). Until 2012, they were considered a single species (Sangster et al., 2012), so their employment as model species allows a direct comparison of the response to DMS in different habitats. Cory’s shearwater (Calonectris borealis Cory 1881), breeds in north Atlantic islands and migrates to different areas of both hemispheres of the Atlantic Ocean (Dias et al., 2011), while the Scopoli’s shearwater (Calonectris diomedea Scopoli, 1769) breeds in the Mediterranean Sea and migrates to the Atlantic Ocean during winter (Brooke, 2004; Ristow et al., 2000). As with all procellariiforms, during breeding they are central place foragers: they must return to the colony either to retrieve a mate or to provision the chick while the foraging grounds remain pelagic (Stephens and Krebs, 1986). This ecological strategy requires high efficiency in locating productive food sources to ensure effective foraging and breeding success. As for the other procellariiforms, olfactory guidance may be
Abbreviations: AOM, medial anterior olfactory region; AOL, anterior olfactory nucleus, lateral part; AOD, anterior olfactory nucleus, dorsal part; AOVP, anterior olfactory nucleus, ventroposterior part; DTT, dorsal tenia tecta layer; E/OV, olfactory ventricle (olfactory part of lateral ventricle); AOP, anterior olfactory nucleus, posterior part; aca, anterior commissure, anterior part; PrL, prelimbic cortex; fmi, forceps minor of the corpus callosum; CPu, caudate putamen (striatum); Nv, navicular nucleus of the basal forebrain; DTT, dorsal tenia tecta; DP, dorsal peduncular cortex; Cg2, cingulate cortex, area 2; LSI, lateral septal nucleus, intermediate part; LSV, lateral septal nucleus, ventral part; LSD, lateral septal nucleus, dorsal part; VDB, nucleus of the vertical limb of the diagonal band; CC, corpus callosum; LSD, lateral septal nucleus, dorsal part; MnPO, median preoptic nucleus; BNST, bed nucleus of the stria terminalis; ac, anterior commissure; LPO, lateral preoptic area; MPA, medial preoptic area; MPO, medial preoptic nucleus; PVA, paraventricular thalamic nucleus, anterior part; PVN, paraventricular hypothalamic nucleus; CM, central medial thalamic nucleus; AM, anteromedial thalamic nucleus; Re, reuniens thalamic nucleus; LH, lateral hypothalamus; RCh, retrochiasmatic area; CA3, ﬁeld CA3 of the hippocampus; PVA, paraventricular thalamic nucleus, anterior part; PVP, paraventricular thalamic nucleus, posterior part; PV, paraventricular thalamic nucleus; IAM, interanteromedial thalamic nucleus; Re, reuniens thalamus nucleus; PH, posterior hypothalamic nucleus; AHC, anterior hypothalamic area, central part; DMD, dorsomedial hypothalamic nucleus, dorsal part; DM, dorsomedial hypothalamic nucleus; VMH, ventromedial hypothalamic nucleus; VMHVL, ventromedial hypothalamic nucleus, ventrolateral part; Arc, arcuate hypothalamic nucleus; ME, median eminence; ML, medial mammillary nucleus, lateral part; VTM, ventral tuberomammillary nucleus; p1PAG, p1 periaqueductal gray; PrC, precommissural nucleus; PAG, periaqueductal gray; Aq, aqueduct; Pn, pontine nuclei; DCIC, dorsal cortex of the inferior colliculus; DLL, dorsal nucleus of the lateral leminiscus; DRD, dorsal raphe nucleus, dorsal part; PTg, pedunculopontine tegmental nucleus; LPB, lateral parabrachial nucleus; DTgP, dorsal tegmental nucleus, pericentral part; DTgC, dorsal tegmental nucleus, central part; CG, central gray; LC, locus coerules; PDTg, posterodorsal tgmental nucleus; PO, periolivary nucleus; py, pyramidal tract; 4V, 4th ventricle; solitary tract nucleus; Rt, reticular nucleus; AP, area postrema.
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persist into adulthood and then linking those brain abnormalities with specific modifications in behavior. Using high-resolution MRI, we observed both increases and decreases in the size of particular brain regions, including the basal forebrain, anterior commissure, amygdala, and the granule cell layer of the dentate gyrus. Amid these widespread changes in brain volume, however, the largest reduction in volume occurred in the OB. We found that this decrease in OB volume dur- ing adulthood may arise from deficits in OB neurogen- esis occurring specifically during early development, as mice with fetal alcohol exposure possessed fewer neural progenitor cells in the SEZ and fewer new cells in the granule cell layer of the OB during the first few postna- tal weeks, but normal numbers of new cells in the OB during adulthood. To determine the long-term conse- quences of abnormal OB development for olfactory behavior, we tested adult mice in an associative olfactory task designed to assess both odor discrimination and odor memory. We found that although fetal alcohol- exposed mice learned and remembered an association between an odor and a reward, they failed to discrimi- nate between odors with a high degree of similarity. Therefore, using a combination of techniques, including structural brain imaging, in vitro and in vivo cell detec- tion methods, and behavioral testing, we found that fetal alcohol exposure affects the initial formation of the OB and produces deficits in olfactory behavior that are evi- dent during adulthood. These findings demonstrate that exposure to alcohol during gestation can have a signifi- cant impact on brain development, thereby leading to disturbances in behavior that persist into adulthood.
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It has been established that several iron-dependent en- zymatic functions are necessary for proper olfaction. For example, neuronal nitric oxide synthase (nNOS), trypto- phan dioxygenase (TDO), indoleamine 2,3-dioxygenase (IDO), 3-hydroxyanthranilic acid oxygenase (3-HAO) and tyrosine hydroxylase (TH) are necessary for olfac- tory signal transduction and all of these proteins require either heme or inorganic iron for structure and activity. Therefore, we designed the present study to investigate the relationship between behavioral olfactory functions and iron deficiency anemia. Behavioral olfactory func- tions in animals are initiated by involuntary inhalation followed by voluntary odorant sampling, or sniffing be- havior, which plays an important role in odor information processing [18-22]. Simple habituation/dis-habituation tests can assess a rodent’s ability to sense and differenti- ate between odors . Using this approach, we deter- mined that iron-deficient rats have prolonged exploratory time for attractive odorants, but not aversive odorants, compared to iron-sufficient controls. A mechanistic model is proposed based on these findings that explains how iron-dependent functions may be involved in controlling and processing of olfactory signal transduction via self and lateral inhibition such that exploratory activity is pro- longed.
hybridization with reelin, Dlx1, Gad67 and tyrosine hydroxylase (Th) probes. Medial is to the right. Immune complexes were visualized with DAB (A-H), or Alexa488 (anti-reelin) and Alexa568 (anti-TBX21, M,N). In situ signals were stained with BM purple substrate. GAP43 and OMP were expressed in OSNs and in the olfactory nerve layer (ONL) in the wild-type bulb. (A-F) GAP43- and OMP-positive OSNs did not extend after the lamina cribrosa and formed the FCM in Fez-deﬁcient embryos. The expression of GAP43 and OMP in the nasal epithelium was not affected in Fez- deﬁcient embryos. Fez-deﬁcient embryos showed an aberrantly wide mitral cell layer, which expresses reelin and TBX21 (K-N), and displayed a reduced number local circuit neurons, which express Gad67 and Th (Q-T), with aberrant positioning. Periglomerular cells and granule cells are marked by arrowheads and arrows, respectively (Q,S).
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some cases, damage can result in irreversible anosmia. Despite advances in our understand- ing of olfaction, effective treatments for com- mon causes of olfactory loss, including head trauma, viral infection, and chronic rhinosinus- itis, aging , neurodegenerative diseases  or environmental factors remain elusive at this time. As a result, we attempted to evaluate the effects of iPSCs on irreversible anosmia. In the present study, we report cell differentia- tion in vitro that mouse iPSCs possess the potency to differentiate into olfactory receptor neurons and mitral/tufted neurons in the indi- rect co-culture system. These differentiated cells express olfactory receptor neuron mark- ers (OMP, GAP43, NCAM) and mitral/tufted neuron markers (TBX21, Iba1) after 14-day co-culture.
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Olfactory sensory neurons innervate the olfactory bulb, where responses to different odorants generate a chemotopic map of increased neural activity within different bulbar regions. In this study, insight into the basal pattern of neural organization of the vertebrate olfactory bulb was gained by investigating the lamprey. Retrograde labelling established that lateral and dorsal bulbar territories receive the axons of sensory neurons broadly distributed in the main olfactory epithelium and that the medial region receives sensory neuron input only from neurons projecting from the accessory olfactory organ. The response duration for local field potential recordings was similar in the lateral and dorsal regions, and both were longer than medial responses. All three regions responded to amino acid odorants. The dorsal and medial regions, but not the lateral region, responded to steroids. These findings show evidence for olfactory streams in the sea lamprey olfactory bulb: the lateral region responds to amino acids from sensory input in the main olfactory epithelium, the dorsal region responds to steroids (taurocholic acid and pheromones) and to amino acids from sensory input in the main olfactory epithelium, and the medial bulbar region responds to amino acids and steroids stimulating the accessory olfactory organ. These findings indicate that olfactory subsystems are present at the base of vertebrate evolution and that regionality in the lamprey olfactory bulb has some aspects previously seen in other vertebrate species.
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olfactory bulb where the density of 5-HT fibers is highest. This means that olfactory sensory neurons that have a higher affinity for pheromones and bile acids could synapse into regions of the olfactory bulb that have a lower density of 5-HT fibers. On a behaviour level, L-amino acids have been shown to play a vital role in detecting food in the olfactory system of many species such as the blackspot sea brem (Hubbard et al., 2011), the catfish (Caprio 1978) and also the sea lamprey (Kleerekoper 1963). Therefore, it is possible that 5-HT acts to modulate lamprey behaviour when attempting to locate food. Perhaps something in the water in the vicinity of an unhealthy prey will stimulate 5-HT and cause it to deter the lamprey by inhibiting its ability to detect the amino acid released by the prey. 5-HT has also been shown to have a role in
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