Olfactory Discrimination Test Research Articles

Investigating individual learning behaviour of dogs during a yes/no detection task

Detection dogs are frequently tested for their ability to detect a variety of targets. It is crucial to comprehend the processes for odour learning and the consequences of training on an expanding set of target scents on performance. To properly evaluate their ability to identify the target, the only true measure is the dogs' initial response to novel sources, since this excludes learning effects. In this study, we evaluated the individual learning processes of three detection dogs that were pre-trained to differentially respond to a faecal sample of a mare in oestrus (S+) and a faecal sample of the same mare in di-oestrus (S-). After reaching criterion during a test with known training samples, the dogs were tested for generalization to a novel source. Average responses to S+ and S- were calculated as a function of presentation sequence, and Signal Detection Theory was used to further analyse characteristic differences in learning. The results of this study suggest that the ability of individual scent detection dogs to learn within an olfactory discrimination test varies considerably. The information obtained in this study could be helpful for mitigation training. We show that through careful monitoring of individual learning processes, the strategy each dog followed becomes apparent: especially the observations on the dogs' responses to first encounters with novel sample sources. This provides us with more detailed information than the more traditional sensitivity and specificity measures and allows us to better predict the dog's capabilities.

Development of a Digital Olfactory Function Test: A Preliminary Study.

Olfactory dysfunction is associated with conditions such as neurodegenerative diseases, diabetes, obesity, autoimmune diseases, mental illnesses, and upper-airway-related diseases. The COVID-19 pandemic necessitated the development of an examiner-independent olfactory function test. We recently developed a digital olfactory function test called Digitalscent (DIGITAL SCENT), which is a kiosk-type device with an integrated hardware system. The protocol follows conventional psychophysical olfactory function protocols, including threshold, discrimination, and identification test subsets. Eight healthy participants without olfactory dysfunction volunteered for the suitability test and completed both the YSK olfactory function and Digitalscent tests. Pearson correlations were determined between the YSK olfactory function and Digitalscent tests. Digitalscent could be implemented as a conventional olfactory function test, and all participants followed the Digitalscent test protocols. Limitations in the threshold and identification test subsets included unfamiliarity of the patients to the digital test and incompleteness in the sophisticated release of odorants. A strength of the identification test subset was the dual sensory stimulation of vision and olfaction. Digitalscent could-without facilitating viral transmission-enable early diagnosis of olfactory dysfunction during respiratory viral pandemics. Future studies with larger sample sizes are warranted to facilitate wider use of this digital olfactory function test.

How volatile composition facilitates olfactory discrimination of fat content in beef and pork

Foods differing in fat content can be distinguished through olfaction alone. The mechanisms underlying the ability of humans to discriminate between foods differing in fat content through olfaction are underexplored. In this study, beef and pork samples were prepared (raw and roasted) with low (muscle tissue; raw: 2–5%; roasted: 5%), medium (muscle tissue with lard; raw: 25–30%; roasted: 36–44%), and high (lard; raw: 40–42%; roasted: 69–70%) fat content. Olfactory triangle discrimination tests and ranking tests were performed to explore whether humans can discriminate and rank fat content of the samples through orthonasal olfaction. Headspace-Solid Phase Micro Extraction-Gas Chromatography-Mass Spectrometry (SPME-GC–MS) was used to characterize the volatile compound composition of the headspace of samples differing in fat content. Partial least-squares regression and partial least squares-discriminant analysis were performed to determine the volatile compounds that were responsible for olfactory fat content discrimination. We found that fat content in both raw and roasted samples can be distinguished through orthonasal olfaction. Perceived odor differences did not always contribute to olfactory identification of fat content. Roasted beef and pork meats with higher fat content had more abundant fatty acids, aldehydes, and ketones. Phthalic acid, isobutyl 2-ropylpentyl ester, and carbon disulfide facilitated the olfactory discrimination of fat content in raw pork and beef samples. 2-Methyl-propanal, benzaldehyde, 1-hydroxy-2-propanone, 2,3-pentanedione, 2,5-octanedione, and 2-butanone contributed to odor differences of roasted beef samples differing in fat content. We conclude that beef and pork samples differing in fat content differ in volatile compound composition of the headspace, and that these differences facilitate discrimination between samples differing in fat content based on olfaction alone.

Dopaminergic neurodegeneration in the substantia nigra is associated with olfactory dysfunction in mice models of Parkinson’s disease

Olfactory dysfunction represents a prodromal stage in Parkinson’s disease (PD). However, the mechanisms underlying hyposmia are not specified yet. In this study, we first observed an early olfactory dysfunction in mice with intragastric rotenone administration, consistent with dopaminergic neurons loss and α-synuclein pathology in the olfactory bulb. However, a much severer olfactory dysfunction was observed without severer pathology in olfactory bulb when the loss of dopaminergic neurons in the substantia nigra occurred. Then, we established the mice models by intrastriatal α-synuclein preformed fibrils injection and demonstrated the performance in the olfactory discrimination test was correlated to the loss of dopaminergic neurons in the substantia nigra, without any changes in the olfactory bulb analyzed by RNA-sequence. In mice with intranasal ferric ammonium citrate administration, we observed olfactory dysfunction when dopaminergic neurodegeneration in substantia nigra occurred and was restored when dopaminergic neurons were rescued. Finally we demonstrated that chemogenetic inhibition of dopaminergic neurons in the substantia nigra was sufficient to cause hyposmia and motor incoordination. Taken together, this study shows a direct relationship between nigral dopaminergic neurodegeneration and olfactory dysfunction in PD models and put forward the understandings that olfactory dysfunction represents the early stage of neurodegeneration in PD progression.

Odor Discrimination as a Marker of Early Alzheimer's Disease.

Olfactory dysfunction is an early symptom of Alzheimer's disease (AD). However, olfactory tests are rarely performed in clinical practice because their diagnostic efficacy in detecting early AD is unclear. To investigate odor discrimination in patients with early AD and the efficacy of olfactory discrimination tests in differentiating these patients from subjects with normal cognition (CN). Thirty patients each with mild dementia due to AD (MD-AD) and mild cognitive impairment due to AD (MCI-AD) and 30 older subjects with CN were enrolled. All participants underwent cognitive examinations (CDR, MMSE, ADAS-Cog 13, and verbal fluency) and odor discrimination tests (Sniffin' Sticks test, Burghart®, Germany). The MD-AD group achieved significantly worse scores on the olfactory discrimination test than the MCI-AD group, and the MCI-AD group achieved significantly worse results than the CN group (p < 0.05). A cut-off score of≤10 had a diagnostic accuracy of 94.44% (95% CI, 87.51-98.17%) in differentiating patients with MCI-AD/MD-AD from subjects with CN and of 91.67% (95% CI, 81.61-97.24%) in differentiating those with MCI-AD from subjects with CN. Our multinomial logistic regression model with demographic data and ADAS-Cog 13 scores as predictor variables correctly classified 82.2% of the cases (CN, 93.3%; MC-AD, 70%; MD-AD, 83.3%); on adding the olfactory discrimination score to the model, the percentage increased to 92.2% (CN, 96.7%; MCI-AD, 86.7%; MD-AD, 93.3%). Odor discrimination is impaired in cases of early AD and continues to deteriorate as the disease progresses. The olfactory discrimination test showed good diagnostic efficacy in detecting early AD.

Comparison of prevalence and evolution of COVID-19 olfactory disorders in patients infected by D614 (wild) and B.1.1.7. Alpha variant: a brief report.

To investigate the prevalence and the evolution of olfactory disorders (OD) related to coronavirus disease 2019 (COVID-19) in patients infected during the first and the second European waves. From March 2020 to October 2020, COVID-19 patients with OD were recruited and followed over the 12-month post-infection. The following data were collected: demographic, treatments, vaccination status, and olfactory function. Olfaction was assessed with the Olfactory Disorder Questionnaire (ODQ), and threshold, discrimination, and identification (TDI) test. Outcomes were compared between patients of the first wave (group 1: wild/D614G virus) and the second wave (group 2: B.1.1.7. Alpha variant) at 1-, 3- and 12-month post-infection. Sixty patients completed the evaluations accounting for 33 and 27 patients in group 1 and 2, respectively. The 1-month TDI score (23.7 ± 5.3) was significantly lower in group 2 compared to group 1 (29.8 ± 8.7; p = 0.017). Proportion of normosmic patients at 1-month post-infection was significantly higher in group 1 compared to group 2 (p = 0.009). TDI scores only significantly increased from 1- to 3-month post-infection in anosmic and hyposmic patients. Focusing on There was a negative association between the 1-month ODQ and the 1-month TDI (rs = - 0.493; p = 0.012). ODQ was a significant predictor of TDI scores at 3- and 12-month post-infection. The 12-month prevalence of parosmia was 60.6% in group 1 and 42.4% in group 2, respectively. There was no significant influence of oral corticosteroid treatment, adherence to an olfactory training and vaccination status on the olfactory outcomes. Patients of the second wave (Alpha B.1.1.7. variant) reported significant higher proportion of psychophysical test abnormalities at 1-month post-infection than patients infected during the first wave (D614G virus).

Inhalation of Cananga odorata essential oil relieves anxiety behaviors in autism-like rats via regulation of serotonin and dopamine metabolism

ObjectiveAnxiety is one of the most common symptoms associated with autistic spectrum disorder. The essential oil of Cananga odorata (Lam.) Hook. f. & Thomson, usually known as ylang-ylang oil (YYO), is often used in aromatherapy as a mood-regulating agent, sedative, or hypotensive agent. In the present study, the effects and mechanisms of YYO in alleviating anxiety, social and cognitive behaviors in autism-like rats were investigated. MethodsThe prenatal valproic acid (VPA) model was used to induce autism-like behaviors in offspring rats. The effectiveness of prenatal sodium valproate treatment (600 mg/kg) on offspring was shown by postnatal growth observation, and negative geotaxis, olfactory discrimination and Morris water maze (MWM) tests. Then three treatment groups were formed with varying exposure to atomized YYO to explore the effects of YYO on the anxiety, social and cognitive behaviors of the autistic-like offspring through the elevated plus-maze test, three-chamber social test, and MWM test. Finally, the monoamine neurotransmitters, including serotonin, dopamine and their metabolites, in the hippocampus and prefrontal cortex (PFC) of the rats were measured using a high-performance liquid chromatography. ResultsOffspring of VPA exposure rats showed autism-like behaviors. In the VPA offspring, medium-dose YYO exposure significantly elevated the time and entries into the open arms in the elevated plus-maze test, while low-dose YYO exposure significantly enhanced the social interaction time with the stranger rat in session 1 of the three-chamber social test. VPA offspring treated with YYO exposure used less time to reach the platform in the navigation test of the MWM test. YYO exposure significantly elevated the metabolism of serotonin and dopamine in the PFC of VPA offspring. ConclusionYYO exposure showed the effects in alleviating anxiety and improving cognitive and social abilities in the offspring of VPA exposure rats. The role of YYO was related to the regulation of the metabolism of serotonin and dopamine.Please cite this article as: Zhang N, Wang ST, Yao L. Inhalation of Cananga odorata essential oil relieves anxiety behaviors in autism-like rats via regulation of serotonin and dopamine metabolism. J Integr Med. 2023; 21(2): 205–214.

Behavioral and Neuropathological Changes After Toxoplasma gondii Ocular Conjunctival Infection in BALB/c Mice.

Ocular infection with Toxoplasma gondii causes toxoplasmosis in mice. However, following ocular infection with tachyzoites, the cause of the accompanying progressive changes in hippocampal-dependent tasks, and their relationship with the morphology and number of microglia, is less well understood. Here, in 6-month-old, female BALB/c mice, 5 μl of a suspension containing 48.5 × 106 tachyzoites/ml was introduced into the conjunctival sac; control received an equal volume of saline. Before and after instillation, all mice were subject to an olfactory discrimination (OD) test, using predator (cat) feces, and to an open-field (OF) task. After the behavioral tests, the animals were culled at either 22 or 44 days post-instillation (dpi), and the brains and retinas were dissected and processed for immunohistochemistry. The total number of Iba-1-immunolabeled microglia in the molecular layer of the dentate gyrus was estimated, and three-dimensional reconstructions of the cells were evaluated. Immobility was increased in the infected group at 12, 22, and 43 dpi, but the greatest immobility was observed at 22 dpi and was associated with reduced line crossing in the OF and distance traveled. In the OD test, infected animals spent more time in the compartment with feline fecal material at 14 and at 43 dpi. No OD changes were observed in the control group. The number of microglia was increased at 22 dpi but returned to control levels by 44 dpi. These changes were associated with the differentiation of T. gondii tachyzoites into bradyzoite-enclosed cysts within the brain and retina. Thus, infection of mice with T. gondii alters exploratory behavior, gives rise to a loss in predator’s odor avoidance from 2 weeks after infection, increased microglia number, and altered their morphology in the molecular layer of the dentate gyrus.

Olfaction and Melatonin: The Use of the Olfactory Discrimination Test.

In order to investigate the role of melatonin in olfactory function, we present the olfactory discrimination test as a simple and low-cost behavioral assessment. The test consists in evaluating the time that each rat spent in two compartments: one has a familiar odor (sawdust with the smell from the animal) and the other one with an unfamiliar odor (clean sawdust). Animals with the normal olfactory functions will discriminate between these two odors and will spend more time in the familiar compartment. We used the olfactory discrimination test to evaluate the role of melatonin receptors expressed in the olfactory bulb of rats. In a previous study, our results have successfully detected an olfactory modulation, by mean of the olfactory discrimination test, promoted by the infusion of melatonin receptor ligands into the olfactory bulb of rats.

Like psychosis, like dementia: Nigella sativa oil enhanced olfactory and amygdalic phenotypes in socially isolated BALB/c mice model of schizophrenia

AbstractBackgroundSocial isolation rearing (SIR) is a developmental schizophrenia model with characteristic behavioral symptoms like anxiety and olfactory deficits influenced by the amygdala and olfactory bulbs respectively. Psychiatric disorders and dementias are often comorbid, with neuropsychiatric disturbances constituting inherent component of Alzheimer’s. As long‐term side effects mar available antipsychotics, novel natural psycho‐dementia drugs are urgently needed. This study thus investigated Nigella sativa (NS) for its impacts on olfactory bulb and amygdalic phenotypes in socially isolated BALB/c mice.MethodFifty (50) male BALB/c mice weaned after 21 days of birth were grouped equally into five. CTRL and NS were reared socially and administered normal saline (1ml/kgbw) and Nigella sativa (1ml/kgbw) respectively. SIR‐NS, NS‐SIR and SIR were socially isolated and administered Nigella sativa (1ml/kgbw) post‐isolation, Nigella sativa pre‐isolation (through maternal exposure) and normal saline respectively. Respective administrations lasted 10 days while social isolation lasted 4 weeks. Amygdalic and olfactory bulb glutamate, GPX and dopamine levels as well as histo‐architecture were investigated in addition to body weights, relative brain weight, temperature, food and water consumption. Olfactory acuity was assayed with olfactory sensitivity and discrimination tests while anxiety levels were assayed with elevated plus maze. Statistical analysis was carried out using one‐way ANOVA at 95% CI.ResultIn addition to increased brain‐body weight ratios, Nigella sativa increased the glutamate and dopamine levels in the amygdala and olfactory bulb of socially isolated mice which were maternally exposed to Nigella sativa (NS‐SIR mice) compared to the untreated but isolated mice. GPX also increased in the amygdala of the NS‐SIR but not in the olfactory bulb. Maternal Nigella sativa exposure prevented olfactory insensitivity in the SIR mice but with no ameliorative effect on the open arm exploration time in the pre‐ or post‐treated mice compared with the untreated isolated mice. NS‐SIR animals exhibited better histoarchitecture than SIR mice, as evidenced by increased neuronal sizes, densities and neuro‐piliary staining.ConclusionSocial isolation modelled olfactory and partial emotional deficits in BALB/c mice similar to schizophrenics. Maternal exposure to Nigella sativa showed significant prophylactic potentials against these deficits especially in olfaction. However, farther isolation distance between the animals is recommended for better results.

Effect of vitamin C treatment on some central nervous system functions in young rats whose mothers treated with hydrogen peroxide during the lactation period

This study was designed to evaluate the effect of vitamin on young rats whose mothers exposed to 1% hydrogen peroxide in drinking water during the lactation period on the function of the nervous system. The study consisted of three groups, Control group, hydrogen peroxide group, vitamin C with hydrogen peroxide group, showed that treatment with hydrogen peroxide for mothers led to significant decrease in the weights of young-rats-age21 days and significant increase in the righting reflex test, cliff avoidance and the olfactory discrimination test in young rats at age of week and also in the onset movement test and at the time of negative geotaxis test in-young-rats age21days. Treatment of mothers with hydrogen peroxide caused significant decrease in open-field activity and number of times standing on backlists during 3minutes and in the approach response, touch and sound of young rats at age 21 days. While, hydrogen peroxide treated group resulted in significant increase in time of negative geotaxis test and hydrogen peroxide had no effect on response of tail pinch as compared to other groups. When treating mothers with vitamin C significant increase in weights of youngsters age21days, as well as in onset of movement test and in number of squares cutoff within 3minutes in open-field activity and number of times standing on backlists during 3minutes in young-rats age 21 days. Also there was significant decrease in righting reflex test, olfactory distinction and negative geotaxis test compared to hydrogen peroxide treated group. It was concluded from the study that vitamin C plays an important role as an antioxidant by improving the nervous system function in young rats their mothers exposed to with hydrogen peroxide in drinking water.

Insulin fast-dissolving film for intranasal delivery via olfactory region, a promising approach for the treatment of anosmia in COVID-19 patients: Design, in-vitro characterization and clinical evaluation

The present work aimed to formulate intranasal insulin fast-dissolving films for treatment of anosmia in patients post COVID-19 infection. Variant films were prepared employing the casting method and using hydroxypropyl methyl cellulose and polyvinyl alcohol. The formulated films were investigated for insulin content, weight variation, surface pH, thickness, folding endurance and disintegration time. In vitro release study was conducted for the selected formulations (F6, F7, F8). A drug/polymer interaction was investigated in the optimized formulation (F7) employing Fourier transform infrared spectroscopy. Clinical study was accomplished for F7 on 20 patients. Sniffin’s and olfactory discrimination tests were used for assessing patients. The formulated films displayed appropriate physical characteristics. F7 showed the shortest disintegration time (50 ± 7 s) and fastest release. It displayed compatibility between the drug and the used polymers. The results of the clinical study revealed a significant increase in the olfactory detection scores and olfactory discrimination values in the intervention group (7.9 ± 1.2, 6.7 ± 0.5 respectively) compared to placebo group (3 ± 0.8, 2.8 ± 1).. Intervention group showed significant differences between these scores before and after treatment while the placebo group did not display any significant differences. Thus, the optimized film can be considered as an auspicious approach for managing post COVID-19 anosmia.

Caffeine Consumption plus Physical Exercise Improves Behavioral Impairments and Stimulates Neuroplasticity in Spontaneously Hypertensive Rats (SHR): an Animal Model of Attention Deficit Hyperactivity Disorder.

Attention deficit hyperactivity disorder (ADHD) is a prevalent and disabling disorder, mainly characterized by hyperactivity, inattention, and impulsivity, but also by olfactory and memory impairments that frequently persist throughout lifetime. The pathophysiology of ADHD is complex, involving several brain regions and neural pathways including alterations in adenosine neuromodulation. The administration of caffeine (a non-selective adenosine receptor antagonist) and physical exercise have been independently pointed as effective approaches for the management of ADHD symptoms. Here, we evaluated the effects of caffeine consumption (0.3mg/mL in drinking water) plus physical exercise in running wheels during 6weeks-starting during either adolescence (30days old) or adulthood (4-5months old)-on behavioral performance (including olfactory discrimination, open field, object recognition, and water maze tests) on the brain levels of monoamines (by high-performance liquid chromatography), on proteins related to synaptic plasticity and on brain-derived neurotrophic factor signaling (by Western blot analysis) in spontaneously hypertensive rats (SHRs), a validated animal model of ADHD. SHRs displayed persistent impairments of olfactory and short-term recognition memory from adolescence to adulthood, which were accompanied by lower levels of synaptosomal-associated protein 25 (SNAP-25) in the prefrontal cortex and hippocampus. The association of caffeine plus physical exercise during adolescence or adulthood restored the olfactory discrimination ability and, in an independent manner, improved short-term recognition memory of SHRs. These benefits were not associated to alterations in locomotor activity or in the hypertensive phenotype. The association of caffeine consumption plus physical exercise during adolescence increased the levels of SNAP-25, syntaxin, and serotonin in the hippocampus and prefrontal cortex, and striatal dopamine levels in SHRs. These results provide new evidence of the potential of caffeine and physical exercise, starting at adolescence or adult life, to improve behavioral impairments and stimulate neuroplasticity in ADHD.

APPL2 Negatively Regulates Olfactory Functions by Switching Fate Commitments of Neural Stem Cells in Adult Olfactory Bulb via Interaction with Notch1 Signaling.

Adult olfactory neurogenesis plays critical roles in maintaining olfactory functions. Newly-generated neurons in the subventricular zone migrate to the olfactory bulb (OB) and determine olfactory discrimination, but the mechanisms underlying the regulation of olfactory neurogenesis remain unclear. Our previous study indicated the potential of APPL2 (adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper 2) as a modulating factor for neurogenesis in the adult olfactory system. In the present study, we report how APPL2 affects neurogenesis in the OB and thereby mediates olfactory discrimination by using both in vitro neural stem cells (NSCs) and an in vivo animal model-APPL2 transgenic (Tg) mice. In the in vitro study, we found that APPL2 overexpression resulted in NSCs switching from neuronal differentiation to gliogenesis while APPL2 knockdown promoted neurogenesis. In the in vivo study, APPL2 Tg mice had a higher population of glial cells and dampened neuronal production in the olfactory system, including the corpus callosum, OB, and rostral migratory stream. Adult APPL2 Tg mice displayed impaired performance in olfactory discrimination tests compared with wild-type mice. Furthermore, we found that an interaction of APPL2 with Notch1 contributed to the roles of APPL2 in modulating the neurogenic lineage-switching and olfactory behaviors. In conclusion, APPL2 controls olfactory discrimination by switching the fate choice of NSCs via interaction with Notch1 signaling.

Olfactory Training Prevents Olfactory Dysfunction Induced by Bulbar Excitotoxic Lesions: Role of Neurogenesis and Dopaminergic Interneurons.

Glutamatergic excitotoxicity is involved in pathologies affecting the central nervous system, including traumatic brain injury (TBI) and neurodegenerative diseases, such as Parkinson's disease (PD), in which olfactory dysfunction is an early symptom. Interestingly, our group has recently shown that bilateral administration of the glutamate agonist, N-methyl-D-aspartate (NMDA) in the olfactory bulbs (OBs) induces an olfactory dysfunction 1week after lesions. Although a wide range of treatments have been attempted, no standard therapy has been established to treat olfactory disorders. Increasing evidence suggests a beneficial effect of olfactory training (OT) in olfactory function. However, the mechanisms underlying OT effects remain unknown. We investigated the effects of OT on the olfactory dysfunction induced by excitotoxicity in bilateral OB NMDA-lesioned animals. We compared OT effects with the ones obtained with neuroprotective therapies (pramipexole and MK801). We studied the underlying mechanisms involved in OT effects investigating the changes in the subventricular zone (SVZ) neurogenesis and in the number of periglomerular dopaminergic interneurons. One week after lesion, NMDA decreased the number of correct trials in the olfactory discrimination tests in the non-trained group (p < 0.01). However, OT performed for 1week after lesions prevented olfactory dysfunction (p < 0.01). Pramipexole did not prevent olfactory dysfunction, whereas MK801 treatment showed a partial recovery (p < 0.05). An increase in SVZ neurogenesis (p < 0.05) associated with an increase in OB dopaminergic interneurons (p < 0.05) was related to olfactory function prevention induced by OT. The present results suggest a role for dopaminergic OB interneurons underlying the beneficial effects of OT improving olfactory dysfunction in bilaterally OB NMDA-lesioned animals.

Food preference and olfactory discrimination tests: A complementary approach to understand the drivers of hedonic responses in dogs

AbstractUnderstanding the food preference of animals remains a challenge in sensory science. Here, a complementary approach combining food preference and food odor discrimination tests was applied to dogs as consumers. This approach was designed to distinguish a lack of preferential choice from a lack of discrimination in dogs. Consumption of four pet food products by a taster dog panel was evaluated. First choice and intake ratio results were strongly linked, suggesting that odor perception influenced the dogs' food consumption. Within this test, two products were preferred by the dogs and favored equally. To provide more depth to the interpretation, we used an olfactometer to measure the dogs' discrimination of the four product odors. A panel of dogs, designated the expert panel, was specially trained in olfactory recognition of one of the two equally preferred products. The main results demonstrated that dogs can discriminate products by olfaction and express the same food preference for different products, even if they have different odors. Moreover, the olfactory experiments allowed us to conclude that the differences in intensity among odors did not affect their discrimination.Practical applicationsThe combination of a two‐bowl consumption test and an olfactory discrimination task using a dual‐port olfactometer appears to be a complementary approach that could help clarify the drivers of animals' liking. In dogs, for example, olfaction is thought to play a major role in food preference. Therefore, using an automated olfactometer technique provides an opportunity to control and modulate the odors presented to the animal and further explore the role of olfaction in the discrimination of different odorants. Thus, the proposed method could be useful to measure the influence of odor on dogs' food selection and to discern a real absence of preference from a lack of olfactory discrimination capacity, which is currently an important methodological obstacle to analyzing the results of two‐bowl consumption tests. In addition, this complementary approach could be transferred to further works dealing with the understanding of food preference mechanisms in other species.

Olfactory deficit as a result of clozapine withdrawal syndrome in an animal model of schizophrenia: preliminary results.

Clozapine is an antipsychotic that produces serious withdrawal effects in schizophrenic patients. Olfactory deficits are well known as part of negative symptoms, but it is not known whether antipsychotic use and/or withdrawal are implicated. Then, we tested clozapine withdrawal in association with two widely used schizophrenia models: Neonatal immune challenge by Polycitidilic-polyinosinic acid (polyI:C) and ketamine. PolyI:C (or saline) was injected subcutaneously in neonatal period, dose of 5 mg/kg from 2 to 6 Post Natal Days, and ketamine or saline at the dose 25mg/kg intraperitoneally (i.p.), daily for 7 days from 53 to 60 post natal day. Clozapine 10mg/kg (or saline) was administered i.p. from 46 to 60 post natal day. Olfactory discrimination test (sensorial and cognitive deficit) was performed at 61 post natal day, 24h after the last injections. The association of PolyI:C, ketamine and clozapine disrupted Olfactory Discrimination, equating time in familiar and non-familiar compartments. PolyI:C plus ketamine increased crossings between compartments. It was produced, for the first time, an olfactory deficit induced by clozapine withdrawal in Wistar rats subjected to schizophrenia animal models.

Olfactory function in an excitotoxic model for secondary neuronal degeneration: Role of dopaminergic interneurons

Secondary neuronal degeneration (SND) occurring in Traumatic brain injury (TBI) consists in downstream destructive events affecting cells that were not or only marginally affected by the initial wound, further increasing the effects of the primary injury. Glutamate excitotoxicity is hypothesized to play an important role in SND. TBI is a common cause of olfactory dysfunction that may be spontaneous and partially recovered. The role of the glutamate excitotoxicity in the TBI-induced olfactory dysfunction is still unknown.We investigated the effects of excitotoxicity induced by bilateral N-Methyl-D-Aspartate (NMDA) OB administration in the olfactory function, OB volumes, and subventricular zone (SVZ) and OB neurogenesis in rats. NMDA OB administration induced a decrease in the number of correct choices in the olfactory discrimination tests one week after lesions (p<0.01), and a spontaneous recovery of the olfactory deficit two weeks after lesions (p<0.05). A lack of correlation between OB volumes and olfactory function was observed. An increase in SVZ neurogenesis (Ki67+ cells, PSANCAM+ cells (p<0.01) associated with an increase in OB glomerular dopaminergic immunostaining (p<0.05) were related to olfactory function recovery.The present results show that changes in OB volumes cannot explain the recovery of the olfactory function and suggest a relevant role for dopaminergic OB interneurons in the pathophysiology of recovery of loss of smell in TBI.

The Association Between Olfaction and Depression: A Systematic Review.

Previous studies on the relationship between olfaction and depression have revealed mixed results. In addition, few have focused on the reciprocity of this association. The aim of this study is to combine depression and olfactory data in two separate patient populations to further understand their association. A systematic literature review was conducted using 3 online databases to identify studies correlating olfaction and depression in patients presenting with either primary depression or primary olfactory dysfunction. For the depressed population, weighted means and standard deviations for the Sniffin' Sticks Test and the 40-item Smell Identification Test were combined using 10 studies. For the olfactory dysfunction population, weighted means of Beck's Depression Inventory were combined using 3 studies. Independent t-tests were used to compare differences between groups. Comparing primary depressed patients with controls, depressed patients showed decreased scores in olfactory threshold (6.31±1.38 vs. 6.78±0.88, P = 0.0005), discrimination (12.05±1.44 vs. 12.66±1.36, P = 0.0073), identification (12.57±0.74 vs. 12.98±0.90, P < 0.0001), and 40-Item Smell Identification Test (35.31±1.91 vs. 37.41±1.45, P < 0.0001). In patients with primary olfactory dysfunction, Beck's Depression Inventory scores were significantly different between patients classified as normosmics, hyposmics and anosmics (5.21±4.73 vs. 10.93±9.25 vs. 14.15±5.39, P ≤ 0.0274 for all 3 comparisons). In conclusion, patients with depression have reduced olfactory performance when compared with the healthy controls and conversely, patients with olfactory dysfunction, have symptoms of depression that worsen with severity of smell loss.

(-)Epigallocatechin-3-gallate prevents the reserpine-induced impairment of short-term social memory in rats.

Reserpine has been confirmed to induce cognitive dysfunction and increase brain neural oxidative stress. Green tea catechins, particularly (-)epigallocatechin-3-gallate (EGCG), have strong antioxidative properties and can protect against numerous oxidative damages. In this study, we examined the possible protective effects of EGCG on reserpine-induced impairment of short-term memory in rats. Reserpine (1 mg/kg, intraperitoneal)-induced memory impairment was assessed using the social recognition task method; locomotor activity and the olfactory discrimination ability were not altered as measured by an open-field test and an olfactory discrimination test, respectively. EGCG treatment (100 and 300 mg/kg, intraperitoneal, for 7 days, starting 6 days before the reserpine injection) could improve the worsened social memory of reserpine-treated rats. Also, EGCG treatment reduced reserpine-induced lipid peroxidation and enhanced the antioxidation power in the hippocampi of reserpine-treated rats. These results suggest a protective effect of EGCG in treating reserpine-induced impairment of memory, most probably through its powerful antioxidative activities. Accordingly, EGCG may hold a clinically relevant value in preventing reserpine-induced cognitive dysfunction.