Odor Identification Research Articles

Sniffing Colors - Color associations for descriptors and odors of the MONEX-40 test.

Research on odor-color associations provides insights into brain processes that integrate attributes from seemingly independent senses, forming crossmodal correspondences. Since multisensory integration is based, among others, on semantic congruency, we aimed to provide a color profile - encompassing hue, saturation, and lightness - for the standardized MONEX-40 test. This color profile will enable the use of odor-congruent or odor-incongruent colors in olfactory-visual studies. In Study 1, participants completed an online survey, selecting colors corresponding to each descriptor in the smell test. The analysis revealed distinct color patterns, highlighting the importance of learning in descriptor-color associations. Study 2 explored color associations for all 40 odors of the MONEX-40 at different time points. Initially, participants reported color associations based solely on odor perception. Then, they identified the odor from a set of four descriptors and reassigned colors after odor identification. Both qualitative and quantitative methods, including statistical tests and ΔE (CIE 2000) analysis, demonstrated shifts in color associations after odor identification, affecting hue, saturation and lightness. This research deepens our understanding of how color associations form in response to various stimuli, including descriptors and odors. The findings have scientific relevance, as mentioned above, but also practical applications in product development, particularly in the food and cosmetics industries, where combining specific colors and odors can enhance product appeal.

Poor Olfaction and Risk of Stroke in Older Adults: The Atherosclerosis Risk in Communities Study.

Poor olfaction may be associated with adverse cerebrovascular events, but empirical evidence is limited. We aimed to investigate the association of olfaction with the risk of stroke in the Atherosclerosis Risk in Communities Study. We included 5799 older adults with no history of stroke at baseline from 2011 to 2013 (75.5±5.1 years, 59.0% female and 22.2% Black). Olfaction was assessed by the 12-item Sniffin' Sticks odor identification test and defined as poor (number correct ≤8), moderate (9-10), or good (11-12). Participants were followed from baseline to the date of the first stroke, death, last contact, or December 31, 2020, whichever occurred first. We used the discrete-time subdistribution hazard model to estimate the marginal cumulative incidence of stroke across olfactory statuses and adjusted risk ratios, accounting for covariates and competing risk of death. After up to 9.6 years of follow-up, we identified 332 incident stroke events. The adjusted marginal cumulative incidence of stroke at 9.6-year follow-up was 5.3% (95% CI, 4.2%-6.3%), 5.9% (95% CI, 4.8%-7.1%), and 7.7% (95% CI, 6.5%-9.1%) for good, moderate, and poor olfaction, respectively. Compared with good olfaction, poor olfaction was significantly associated with higher stroke risk throughout follow-up, albeit the association modestly attenuated after 6 years. Specifically, the adjusted risk ratios were 2.14 (95% CI, 1.22-3.94) at year 2, 1.98 (95% CI, 1.43-3.02) at year 4, 1.91 (95% CI, 1.43-2.77) at year 6, 1.49 (95% CI, 1.17-2.00) at year 8, and 1.45 (95% CI, 1.16-1.95) at year 9.6. Results were robust in multiple subgroup and sensitivity analyses. In older adults, poor olfaction assessed by a single olfaction test was associated with the higher risk of stroke in the next 10 years.

Olfactory Function and Frailty in Older Adults.

This study investigated the relationship between olfactory impairment and frailty among 5,231 (mean age 75.3 (SD 5.0), 59% women, 22% Black) participants of the Atherosclerosis Risk in Communities (ARIC) Study cohort located in the U.S.. Olfactory function, assessed from the 12-item Sniffin' Sticks Odor Identification Test at Visit 5 (2011-2013), was categorized as poor (0-8), moderate (9-10) and good (11-12). Frailty was assessed using both the Fried Frailty Phenotype and the Cumulative Frailty Index. Findings revealed that good olfaction was significantly associated with lower odds of frailty (OR=0.29, 95% CI [0.22, 0.39]) and prefrailty (OR= 0.52, 95% CI [0.45, 0.61]) in cross-sectional analyses. Results were robust to adjustment for all covariates. Longitudinal analyses, including 1,519 participants who were robust at study baseline, similarly showed a dose-response pattern, with improved olfaction associated with decreased odds of experiencing prefrailty (OR=0.63 95% CI [0.48, 0.83]) or frailty (OR=0.50, 95% CI [0.25, 1.02]). Further research is needed to elucidate the mechanisms linking olfaction and frailty and explore potential interventions.

What does it mean when the pleasant smells come and go? Correlation between UPSIT odor identification status and fluctuation of non-motor symptoms in Parkinson's disease.

Parkinson's disease (PD) is characterized by motor and non-motor symptoms, including olfactory dysfunction. Prior studies have shown that olfaction deteriorates with disease progression, however fluctuations in olfaction and related PD symptoms have been less explored. This study aimed to investigate correlations between changes in odor identification ability and PD symptoms. PD patients recruited from Taichung Veterans General Hospital underwent at least two consecutive Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) and University of Pennsylvania Smell Identification Test (UPSIT) evaluations. The patients were grouped based on changes in olfactory identification ability between evaluations, and fluctuations in PD symptoms were compared between groups. Ninety-seven PD patients with 114 complete sets of data were analyzed. Significant divergent results were observed between changes in five MDS-UPDRS non-motor subscores and the conversion status of five pleasant odors, including anxiety vs. bubble gum, apathy vs. banana, dizziness vs. coconut, urination vs. root beer, and dopamine dysregulation syndrome (DDS) vs. grape. Fluctuations in the ability to detect pleasant odors, may have a complex interaction with other non-motor symptoms, including in the neurobehavioral and autonomic domains. Serial monitoring of olfactory function, particularly with pleasant odors, may provide valuable insights for tracking non-motor symptoms in PD and warrants further investigation into their therapeutic implications.

Differences in Perceived Versus Actual Sensory Perception in Avoidant/Restrictive Food Intake Disorder.

Individuals with avoidant/restrictive food intake disorder (ARFID) self-report heightened sensitivity to taste and smell, but neither phenomenon has been systematically explored in the laboratory. We hypothesized that, compared to healthy controls (HC, n = 34), children, adolescents, and adults with full/subthreshold ARFID (n = 100; ages 9 to 23 years) would self-report heightened response to taste/smell stimuli and exhibit stronger bitter taste perception and heightened smell perception in performance-based tasks, and these differences would be especially prominent in those with the ARFID-sensory sensitivity presentation. We measured self-reported sensitivity to taste/smell with the adolescent/adult sensory profile (AASP). We measured performance-based bitter taste perception with the regional taste intensity test (RTIT) and 6-N-propylthiouracil (PROP) test, and olfactory performance with the Sniffin' Sticks test (including the odor threshold, odor detection, and odor identification subscales). As expected, the ARFID group self-reported heightened response to taste/smell on the AASP, compared to HC, with an especially large effect size in the subset with the ARFID-sensory sensitivity presentation. Contrary to hypotheses, on performance-based measures, neither the ARFID group-nor the ARFID-sensory sensitivity group specifically-demonstrated heightened sensitivity to bitter taste on the RTIT or PROP tests, nor heightened smell perception on the Sniffin' Sticks test. These first laboratory findings in a clinically diagnosed sample of individuals with full/subthreshold ARFID highlight the discrepancy between perceived versus actual sensitivity to taste/smell stimuli. Future research should explore whether this discrepancy can be replicated and therapeutically leveraged to facilitate successful food exposures.

Olfactory dysfunction in schizophrenia and other psychotic disorders: A comprehensive and updated meta-analysis.

Olfaction plays a key role in our daily life, influencing food enjoyment, threat detection, mood and social relationships. Numerous studies have provided evidence of abnormal olfactory function in schizophrenia and other psychotic disorders. This pre-registered meta-analysis was conducted to (a) provide an updated overview of olfactory function in schizophrenia-spectrum disorders, and (b) examine the modulatory effects of demographic and clinical variables on distinct olfactory abilities. We complied with the PRISMA guidelines, searching throughout PubMed, MEDLINE, and PsycInfo, until the 12th of August 2023. A total of 73 publications were included, comprising data from 3282 patients and 3321 healthy controls. Results revealed that (a) patients performed significantly worse in higher-order olfactory tests (identification and discrimination) compared to healthy controls, while no differences were observed in odor sensitivity; (b) patients' performance in odor identification was moderated by education, as well as disease duration and negative symptoms. Our findings support the presence of olfactory impairments in schizophrenia-spectrum disorders, leading to significantly poorer performance in both odor identification and discrimination, but not sensitivity, when compared to healthy controls.

Six-week engagement in after-school activities involving chemosensory education does not affect olfactory abilities and personal significance of olfaction in 9-11-year-olds: Preliminary evidence.

Chemosensory learning is a lifelong process of acquiring perceptual expertise and semantic knowledge about chemical stimuli within the everyday environment. In the research context, it is usually simulated using olfactory training, which typically involves repeated exposure to a set of odors over a period of time. Following olfactory training, enhanced olfactory performance has been observed in adults, and similar evidence is beginning to emerge in children. However, the literature is scant concerning the effects of interventions that more closely resemble how chemosensory experience is acquired in daily life. Since children's chemosensory ecology appears to play a crucial role in olfactory development, we investigated whether engaging in activities that stimulate the chemical senses enhances olfactory performance and metacognition. To this end, we invited 20 children aged 9-11 years to participate in teacher-assisted after-school activities for 30-60 minutes a day for six weeks. During the odd weeks, the children appraised herbal and spice blends and used them to prepare dishes and make beauty products. During the even ones, they explored the city by smellwalking and created smellscape maps. The educational outcomes were evaluated using the Sniffin' Sticks test for odor identification and discrimination and the Children's Personal Significance of Olfaction. Bayesian analyses did not reveal any compelling evidence in support of the alternative hypothesis that children in the chemosensory education group outperform those in the comparison group at the post-test. Rates of reliable increase but also decrease in performance on the Sniffin' Sticks identification and discrimination tests were similar in both groups. We corroborated the previous findings regarding girls' and older children's greater proficiency at identifying odors and the female keener interest in the sense of smell. We offer several practical suggestions researchers may want to consider to tailor their research protocols to reflect more closely the broader context in which chemosensory learning takes place and better capture the nuanced outcomes of such interventions.

Performance of a smell identification test vs. the mini‐mental status exam for the detection of dementia and cognitive impairment among ethnically diverse persons with cognitive concerns in primary care

AbstractBackgroundEarly detection of dementia and cognitive impairment is recommended for persons 65 years and older during wellness primary care visits. The importance of early detection has increased with the availability of new treatments for early Alzheimer's disease (AD). However, there is no clear approach for early detection in primary care. Odor identification deficits predict AD in epidemiological studies and may be useful for early detection. Our objective was to compare the accuracy of a short odor identification test with a short cognitive screening test for the detection of dementia and cognitive impairment in elderly persons with cognitive concerns.MethodThis was a cross‐sectional study of 600 participants 65 years and older, without known mild cognitive impairment (MCI) or dementia, with cognitive concerns, attending primary care practices in New York City. The odor identification test was the Brief Smell Identification Test (BSIT). The comparator test was the Mini Mental Status Exam II (MMSE). Cognitive diagnoses were made using the National Alzheimer’s Coordinating Center Uniform Data set (NACC‐UDS) version 3 forms with slight modifications by a diagnosis consensus committee. Test performance was compared using Receiver Operating Characteristic analyses.ResultThe mean age of the sample was 72.65 ± 6.31 years, 73.3% were female, 63.3% were Hispanic, 17.5% non‐Hispanic Black, and 27.0% non‐Hispanic White; 23.5% had normal cognition, 27.6% had cognitive impairment‐not mild cognitive impairment (MCI), 31.1% had amnestic MCI, 5.6% had non‐amnestic MCI, and 12% had dementia. The MMSE was superior to the BSIT in detecting dementia (AUC 0.89 vs 0.78, p =0.0007, Figure Panel A) and any cognitive impairment (AUC 0.79 vs 0.63, p <0.0001, Figure Panel B). Combining abnormal scores in the BSIT (< 9) to MMSE (< 24) improved the MMSE’s specificity (0.98 combined vs. 0.92 MMSE alone) and positive predictive value (PPV) in detecting cognitive impairment (0.98 combined vs. 0.95 MMSE alone).ConclusionThe MMSE was superior to the BSIT in detecting dementia and cognitive impairment in primary care but using both tests improved specificity and PPV for identifying persons with subjective complaints needing further cognitive and biomarker evaluation.

Characteristics of subjective olfactory dysfunction and imaging features in patients with traumatic olfactory disorders: a retrospective case-control study.

Olfactory dysfunction caused by head trauma poses significant challenges in clinical diagnosis and treatment. The primary difficulty arises from direct injuries to olfactory-related brain tissues. Although imaging provides the most direct method to evaluate such injuries, there is no standardized international diagnostic criterion for olfactory dysfunction based on imaging. We designed this study to compare the subjective olfactory function differences and brain gray-matter (GM) and white-matter (WM) volume differences between patients with traumatic olfactory dysfunction and those with other types of olfactory dysfunction and to determine the characteristics of subjective olfactory dysfunction and imaging features in patients with traumatic olfactory disorders. The findings of this study can provide a theoretical basis for the diagnosis of traumatic olfactory disorders. This ethics committee-approved, retrospective case-control study included 56 patients with traumatic olfactory dysfunction (trauma group) and 45 patients with other types of olfactory dysfunction (e.g., postinfection, nasal inflammation, idiopathic disease). The "Sniffin' Sticks" olfactory function test was used to analyze the subjective olfactory function differences between the two groups, and voxel-based morphometry (VBM) was used to compare the GM volume (GMV) and WM volume (WMV) of brain regions between the two groups. (I) There was no statistical difference in age distribution between the trauma group (41.55±11.77 years) and the control group (38.87±14.37 years; P>0.05). (II) The trauma group had significantly lower total scores and subtest scores on the Sniffin' Sticks olfactory test compared to the control group [odor threshold test (OT): 1.04±0.33 vs. 1.67±1.42; odor discrimination test (OD): 2.93±2.25 vs. 5.42±3.66; odor identification test (OI): 2.77±1.94 vs. 6.71±3.55; total scores: 6.74±3.91 vs. 13.81±7.63; all P values <0.05]. (III) Compared with the control group, the trauma group had significantly reduced GMV and WMV in the bilateral orbitofrontal cortex, bilateral anterior cingulate gyrus, bilateral cingulate gyrus, bilateral rectus gyrus, bilateral olfactory cortex, right superior frontal gyrus, bilateral insula, bilateral caudate nucleus, and bilateral thalamus [Pfamily-wise error (FWE)<0.05]. (IV) There was a significant positive correlation between the odor identification function scores and GMV in certain brain regions (PFWE<0.05), and the GMV in these regions was reduced in the trauma group compared to the control group. Compared to patients with other types of olfactory dysfunction, patients with traumatic olfactory dysfunction have poorer subjective olfactory functions and more severe damage to olfactory-related brain regions, including the bilateral orbitofrontal cortex, anterior cingulate gyrus, cingulate gyrus, rectus gyrus, insula, and olfactory cortex. The olfactory nerve damage in these brain regions can be used as a basis for the diagnosis of traumatic olfactory disorders.

The neural substrate linking olfactory deficits to cognitive decline in MCI

AbstractBackgroundA combination of impairments in odor threshold and discrimination, which are both predominantly sensory level functions, and olfactory cognition contribute to age‐related odor‐identification deficits. However, in Alzheimer’s disease (AD), odor identification is more impaired compared to sensory‐level olfactory functions. We, therefore, hypothesized that match and mismatch olfactory fMRI tasks could be used to isolate areas of odor‐identification and that these areas would include primary as well as secondary olfactory structures. We combined functional magnetic resonance imaging (fMRI) with an olfactory detection task to investigate the neural substrates underlying odor identification.MethodTwenty‐five healthy controls and eighteen MCI subjects (Table 1) took part in an olfactory fMRI odor detection task. The task required subjects to press a button with their right index finger to identify an odorant (i.e., oddball) from a list of distractors. An out of magnet olfactory identification and threshold test was also conducted. This multiple‐choice test was used to measure a participants’ ability to identify twenty different odors.ResultA contrast of HC&gt;MCI, for all odor conditions, yielded activation in brain regions shown in Figure 1C. These regions were used in a subsequent correlation analysis. The left supramarginal gyrus was included based on a study where the TPJ area (which includes parts of the supramarginal and superior temporal gyrus) was highly active in the left hemisphere. A correlation analyses using both HC and MCI showed significant positive correlations between activity in the L supramarginal, L superior temporal, L TPJ and L inferior frontal orbital areas, and out‐of‐magnet olfactory identification scores (Figure 2).ConclusionOur novel fMRI task elicited robust activation in higher‐order olfactory structures. Since Lower activation in these regions correlated with lower ID scores across the entire cohort. HC shows greater activity in higher order brain regions, suggesting an impaired top‐down identification mechanism in MCI. There seems to be a separation between HC and MCI in Figure 2. This will be further investigated using a larger sample size.

Comparison of olfactory and cognitive measures to neuroimaging biomarkers in the prediction of cognitive decline and dementia in the MCSA cohort

AbstractBackgroundInexpensive, non‐invasive tests may improve the identification of persons at increased risk for cognitive decline and dementia. We compared impairment in odor identification and global cognition with neuro‐imaging biomarkers to predict cognitive decline and dementia in the population‐based Mayo Clinic Study of Aging (MCSA).MethodAt the 2008 assessment, 647 participants who were ≥ 55 years old with at least one follow‐up had the following procedures: modified Blessed Information‐Memory‐Concentration Test (BIMCT), 12‐item Brief Smell Identification Test (BSIT), brain magnetic resonance imaging (MRI), and Positron Emission Tomography (PET) amyloid imaging with 11C‐Pittsburgh compound B (11C‐PiB). A subsample (n=556) also had 18F‐fluorodeoxyglucose (18F‐FDG) PET scans. The utility of these baseline measures to predict cognitive decline (cognitively unimpaired to mild cognitive impairment [MCI] or dementia, or MCI to dementia) was examined during follow‐up (mean 8.1 SD 3.4 years). Transition to dementia was a secondary outcome.ResultAmong 647 participants without dementia (mean age 74.0 SD 8.1 years; 54.4% male) at baseline, 102 participants manifested cognitive decline and 34 participants transitioned to dementia. In Cox regression survival analyses for cognitive decline, PiB PET showed the strongest predictive utility (hazard ratio HR 5.05, 95% CI = 3.32‐7.69, p&lt;.001). Impaired BSIT (HR 3.46, 95% CI = 2.34‐5.11, p&lt;.001), impaired BIMCT (HR 3.63, 95% CI 2.46‐5.36, p&lt;.001), MRI and FDG measures were also significant predictors. After adjusting for age, sex and education, these predictors remained significant with attenuated effects (PiB HR 3.89, 95% CI 2.54‐5.95, p&lt;.001; BSIT HR 2.77, 95% CI 1.85‐4.14, p&lt;.001; BIMCT HR 3.3, 95% CI 2.21‐4.95, p&lt;.001). After adding these demographic variables in the model, the combination of BSIT and BIMCT showed strong predictive utility (C‐index=0.85), similar to PiB PET (C‐index=0.84). Combining all predictors showed a C‐index of 0.89. These measures showed similar but stronger results for dementia transition.ConclusionTests of global cognition and odor identification provide a brief, non‐invasive, inexpensive method comparable to PET amyloid imaging for identifying community‐dwelling persons likely to decline cognitively or transition to dementia. Other potential uses for this combination include identification of persons likely to benefit from disease‐modifying medications and determination of eligibility for prevention trials.

Associations of load and progression of imaging markers of microvascular lesions and neurodegeneration with odor identification decline: a population‐based study

AbstractBackgroundOlfactory deficits are predictive of cognitive decline and dementia. Previous studies have linked brain magnetic resonance imaging markers of neurodegeneration to olfactory deficits in aging; however, these studies analyzed cross‐sectional data for markers, olfaction, or both. Furthermore, potential cerebrovascular contributions to understanding why olfactory deficits predict dementia remain unexplored. We aimed to examine whether markers of microvascular lesions and neurodegeneration and their progression are associated with the rate of olfactory decline in community‐dwelling older adults.MethodParticipants were 405 individuals (mean age=70.2 years; 60% females) from the Swedish National study on Aging and Care in Kungsholmen (SNAC‐K) who were free from dementia at baseline. We analyzed microvascular lesions (presence of lacunes, white matter hyperintensities volume, global perivascular spaces [PVS] count) and neurodegeneration (lateral ventricular, hippocampal, and total gray matter volumes) markers, available up to 6 years and an olfactory measure (Sniffin’ Sticks odor identification task), available up to 15 years. Additionally, we assessed summary scores for microvascular lesions and neurodegeneration load (range 0–3), accounting for all markers of each category (1 point for its presence or for being in the worst quartile, as appropriate). Data were analyzed with linear mixed‐effects models.ResultAfter adjustment for sociodemographic (age, sex, and education) and extra covariates (smoking status and semantic memory), a higher global PVS count (β =‐0.041; 95% CI, ‐0.077 to ‐0.005) and a high load (≥2 points) of neurodegeneration (β=‐0.112; 95% CI, ‐0.221 to ‐0.002) at baseline were associated with a faster olfactory decline. Longitudinally (n=228), faster accumulation of PVS (β=‐1.812; 95% CI, ‐3.474 to ‐0.150), faster hippocampal atrophy (β=1.348; 95% CI, 0.413 to 2.283), and an increment from low (≤1 point) to high load for microvascular lesions (β=‐0.167; 95% CI, ‐0.327 to ‐0.007) and neurodegeneration (β=‐0.206; 95% CI, ‐0.321 to ‐0.092) were associated with an accelerated olfactory decline.ConclusionBoth microvascular lesions and neurodegeneration are longitudinally associated with olfactory decline in aging. This relationship supports the notion that olfactory deficits could be valuable as an early marker for dementia. More longitudinal studies are needed to untangle the mechanisms in play between cerebral vascular burden, atrophy, and olfaction.

Associations of load and progression of imaging markers of microvascular lesions and neurodegeneration with odor identification decline: a population‐based study

Associations of load and progression of imaging markers of microvascular lesions and neurodegeneration with odor identification decline: a population‐based study

Reduced Bitter Taste and Enhanced Appetitive Odor Identification in Individuals at Risk for Alcohol Use Disorder: National Health and Nutrition Examination Survey (NHANES) 2013-2014.

An inability to correctly perceive chemosensory stimuli can lead to a poor quality of life. Such defects can be concomitant with excess alcohol consumption, but a large-scale cohort study linking these effects is lacking. This study aimed to investigate the impact of chronic alcohol consumption on chemosensory function by analyzing data from the NHANES 2013-2014, involving 395 participants categorized by alcohol intake behavior: 219 no-intake, 136 light-intake, and 40 risky-intake groups. Chemosensory function was assessed using a self-reported Chemosensory Questionnaire along with objective tests for taste (quinine solution) and smell (appetitive and hazardous odors). Adjusted regression analyses were conducted, controlling for age, gender, smoking status, and multiple pairwise comparisons. Weighted regression analyses were also performed. Risky drinkers had significantly lower odds of identifying quinine (bitter taste) compared to light drinkers (OR = 0.37, p-adjusted = 0.04). Risky drinkers also had higher odds of identifying appetitive odors like strawberry (OR = 5.44, p-adjusted = 0.03) but lower odds for detecting hazardous odors like natural gas (OR = 0.11, p-adjusted = 0.001) compared to light drinkers. Additionally, light drinkers identified the leather scent more effectively than no drinkers (OR = 2.54, p = 0.02). Chronic alcohol consumption, particularly at risky levels, is associated with altered chemosensory function. These findings emphasize the importance of assessing chemosensory symptoms in individuals with alcohol-related behaviors.

Innovative Features in Odor Identification Device

Innovative Features in Odor Identification Device

Clinical efficacy of olfactory training using aromatic traditional Chinese medicine in managing olfactory dysfunction induced by SARS-CoV-2.

The aim of this study is to assess the clinical efficacy of olfactory training using aromatic traditional Chinese medicine (TCM) for addressing severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2)-induced olfactory dysfunction, while also exploring the factors that influence the observed efficacy. 172 outpatients with SARS-CoV-2-related olfactory dysfunction were randomized into two groups. The experimental group received olfactory training with TCM aromatics (ginger, Pericarpium Citri Reticulatae, Santali Albi Lignum, Styrax), while the control group used non-TCM aromatics (phenyl ethanol-rose, menthol-mint, citronellal-lemon, eugenol-clove) for 24 weeks. Olfactory function was assessed using the Sniffin' Sticks test and TDI (threshold-discrimination-identification) scores at baseline, 1, 3, and 6 months post-treatment. Response rates at 1, 3, and 6 months post-treatment were 3.66%, 25.61%, and 43.90% in the experimental group, and 4.94%, 23.46%, and 43.21% in the control group. The TDI scores of the experimental group and the control group were statistically different before and after treatment. At 3 and 6 months post-treatment, TDI scores increased significantly, with enhanced odor discrimination and identification capabilities in both groups compared to pre-treatment, while the odor detection threshold was not improved compared with that before treatment. At the 3- and 6-month follow-ups, experimental group showed significantly higher self-rated sleep and anxiety scores than controls, indicating notable improvement in both after treatment. Olfactory training with aromatic TCM offers an effective treatment for SARS-CoV-2-induced olfactory dysfunction, improving odor discrimination, identification without significant differences compared to conventional aromatics, besides, it may also improve anxiety and sleep quality.

Comparison of brief olfactory and cognitive assessments to neuroimaging biomarkers in the prediction of cognitive decline and dementia in the MCSA cohort.

We evaluated impaired odor identification and global cognition as simple, cost-effective alternatives to neuroimaging biomarkers to predict cognitive decline and dementia in the Mayo Clinic Study of Aging. Six hundred forty-seven participants (mean 8.1, standard deviation 3.4 years' follow-up) had the following baseline procedures: modified Blessed Information Memory Concentration Test (BIMCT), 12-item Brief Smell Identification Test (BSIT), structural brain magnetic resonance imaging (MRI), and positron emission tomography (PET) imaging with 11C-Pittsburgh compound B (11C-PiB) and fluorodeoxyglucose (FDG; subset). Cognitive decline developed in 102 participants and dementia in 34 participants. In survival analyses, PiB PET showed robust prediction for cognitive decline. Impaired BSIT, impaired BIMCT, MRI, and FDG measures were also significant predictors. The combination of demographics + BSIT + BIMCT showed strong predictive utility (C-index 0.81), similar to demographics + PiB PET (C-index 0.80). Similar but stronger results were obtained for prediction of dementia. Impairment in both odor identification test and global cognition was comparable to PiB PET for predicting cognitive decline and dementia. In 647 participants in the population-based Mayo Clinic Study of Aging, several clinical markers and biomarkers each predicted cognitive decline or dementia during an average 8 years of follow-up. The combination of the demographic variables of age, sex, and education with a brief odor identification test (BSIT) and a global cognitive test (Blessed Information Memory Concentration Test) showed strong predictive utility (C-index 0.81) for cognitive decline that was similar to the demographic variables combined with Pittsburgh Compound B amyloid imaging (C-index 0.80). Combining a brief odor identification test with a brief cognitive test needs consideration as a simple, cost-effective option in the clinical assessment of individuals at risk of cognitive decline and dementia, as well as a potential tool to identify individuals who may benefit from disease-modifying treatments and to screen participants for prevention trials.

Single-neuron representations of odours in the human brain

Olfaction is a fundamental sensory modality that guides animal and human behaviour1,2. However, the underlying neural processes of human olfaction are still poorly understood at the fundamental—that is, the single-neuron—level. Here we report recordings of single-neuron activity in the piriform cortex and medial temporal lobe in awake humans performing an odour rating and identification task. We identified odour-modulated neurons within the piriform cortex, amygdala, entorhinal cortex and hippocampus. In each of these regions, neuronal firing accurately encodes odour identity. Notably, repeated odour presentations reduce response firing rates, demonstrating central repetition suppression and habituation. Different medial temporal lobe regions have distinct roles in odour processing, with amygdala neurons encoding subjective odour valence, and hippocampal neurons predicting behavioural odour identification performance. Whereas piriform neurons preferably encode chemical odour identity, hippocampal activity reflects subjective odour perception. Critically, we identify that piriform cortex neurons reliably encode odour-related images, supporting a multimodal role of the human piriform cortex. We also observe marked cross-modal coding of both odours and images, especially in the amygdala and piriform cortex. Moreover, we identify neurons that respond to semantically coherent odour and image information, demonstrating conceptual coding schemes in olfaction. Our results bridge the long-standing gap between animal models and non-invasive human studies and advance our understanding of odour processing in the human brain by identifying neuronal odour-coding principles, regional functional differences and cross-modal integration.

Comparative analyses of post-infectious olfactory dysfunction between COVID-19 and non-COVID-19 cases

To identify the differences between COVID-19-associated and non-COVID-19-associated olfactory dysfunction (OD), we analyzed demographic and clinical characteristics based on the causative virus (COVID versus non-COVID groups) in patients with post-infectious olfactory dysfunction (PIOD) who underwent the olfactory questionnaire and olfactory function test. Out of 169 patients with PIOD, 99 were diagnosed with COVID-19 (COVID group), while 70 were not (non-COVID group). The COVID group was younger and had a higher percentage of male patients as well as patients with parosmia than the non-COVID group. In the initial olfactory function tests, the TDI, discrimination and identification scores were significantly higher in the COVID group than in the non-COVID group. TDI scores were significantly increased in patients with PIOD after treatment, regardless of the group. The threshold score was significantly increased by 1.38 in the COVID group while the identification score was significantly increased by 2.67 in the non-COVID group. Patients with COVID-19-associated OD were younger in age, tended to be male, had a higher incidence of parosmia, and had better initial olfactory function test results compared to those with non-COVID-19-associated OD. Following treatment, odor detection threshold improved in the COVID group, whereas odor identification improved in the non-COVID group.

Taste and smell are associated with dietary intake, eating behavior, nutritional status, and health-related quality of life in children with cancer

Background & aimsSmell and taste changes are frequently reported bothersome treatment symptoms during treatment for childhood cancer and assumed to influence outcomes such as food intake. Since nutritional status of children with cancer is already vulnerable, any detrimental effects on food intake should be prevented. Therefore, understanding the exact relationship between chemosensory changes and dietary intake, eating behavior, and other domains such as health-related quality of life (HRQoL), is important for improving outcomes. MethodsIn this longitudinal study, we followed 87 childhood cancer patients treated for hematological, solid, or brain malignancies. Smell (odor threshold and odor identification) and taste function (total taste score) were objectively investigated using commercial Sniffin’ Sticks and Taste Strips respectively, and by self-report. Dietary intake was measured using a 3-day food dairy. For nutritional status, BMI expressed as standard deviation scores was derived from medical records. Eating behavior and HRQoL were assessed by the Behavioral Pediatrics Feeding Assessment Scale (BPFAS) and PedsQL 4.0 Generic Core Scales, respectively. Measurements were taken approximately 6 weeks (T0), 3 months (T1), 6 months after starting chemotherapy (T2), and 3 months after termination of chemotherapy or maintenance phase for children with acute lymphoblastic leukemia (ALL) (T3). Dietary intake, eating behavior, nutritional status, and HRQoL were modelled over time using mixed model analysis. Associations between smell and taste (objective and self-report), as well as patient characteries were studied. ResultsEnergy intake significantly increased during the study period, with a higher age, BMI, and total taste scores associated to this increase. Boys had higher energy intake compared to girls. Eating behavior scores significantly declined, indicating less eating problems. Age, pre-diagnosis eating behavior, self-reported smell changes, and tube feeding were associated to eating behavior. BMI significantly increased, with a higher BMI at diagnosis to be related to a higher BMI during the study period. A lower BMI was found in children receiving tube feeding and self-reported taste changes. HRQoL improved during the study period, with lower HRQoL in children receiving tube feeding and self-reported taste changes. ConclusionBoth objective and subjective measures of taste and smell influence dietary intake, eating behavior, nutritional status, and HRQoL. Individual dietary advice and coping strategies are warranted to prevent detrimental effects of chemosensory changes on food intake and clinical outcomes in children with cancer.