SwePub - search: WFRF:(Lundström Johan N.)

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1.	Hsieh, Julien W., et al. (author) Can MRI predict olfactory loss and improvement in posttraumatic olfactory dysfunction? 2024 In: Rhinology. - 0300-0729 .- 1996-8604. ; 62:2, s. 172-182 Journal article (peer-reviewed)abstract BACKGROUND: Although most patients with post-traumatic olfactory dysfunction (PTOD) undergo MRI, there is no consensus about its diagnostic or prognostic value.The aims were: 1) to classify the extent of post-traumatic neurodegeneration; 2) todetermine its relationship with chemosensory dysfunction (smell, taste, trigeminal); and 3) to establish whether MRI can predict olfactory improvement. METHODOLOGY: We conducted a retrospective cohort study based on a series of 56 patients with PTOD. All patients underwent validated psychophysical tests of their smell, taste, and trigeminal functions, otorhinolaryngologic evaluation, and MRI. An experiencedradiologist blinded to patient data evaluated 40 chemosensory-relevant brain regions according to a four-point scale (0=no lesion to 3=large lesion). Follow up data after 4 years (on average) were available in 46 patients. RESULTS:The cluster analysis showed 4 brain lesion patterns that differed in lesion localization and severity. They are associatedwith diagnostic categories: anosmia, hyposmia and normosmia. Two clusters were highly specific for anosmia (100% specificity)and could accurately predict this condition (100% positive predictive value). No clusters were associated with trigeminal or tastedysfunction. Regarding improvement, 72.7% of patients in the cluster with mild lesions experienced subjective and measurable olfactory improvement whereas this was only the case in 21.7-37.5% of patients with larger lesions. The odds of subjective smellimprovement were 5.9 times higher in patients within the milder cluster compared to larger ones. CONCLUSIONS: The analysis of brain lesions in PTOD allows corroboration of smell test results and prediction of subjective and measurable improvement.
2.	Schriever, Valentin A., et al. (author) Development of an International Odor Identification Test for Children : The Universal Sniff Test 2018 In: The Journal of Pediatrics. - : Elsevier BV. - 0022-3476 .- 1097-6833. ; 198, s. 265-272 Journal article (peer-reviewed)abstract ObjectiveTo assess olfactory function in children and to create and validate an odor identification test to diagnose olfactory dysfunction in children, which we called the Universal Sniff (U-Sniff) test.Study designThis is a multicenter study involving 19 countries. The U-Sniff test was developed in 3 phases including 1760 children age 5-7 years. Phase 1: identification of potentially recognizable odors; phase 2: selection of odorants for the odor identification test; and phase 3: evaluation of the test and acquisition of normative data. Test-retest reliability was evaluated in a subgroup of children (n = 27), and the test was validated using children with congenital anosmia (n = 14). Results Twelve odors were familiar to children and, therefore, included in the U-Sniff test. Children scored a mean +/- SD of 9.88 +/- 1.80 points out of 12. Normative data was obtained and reported for each country. The U-Sniff test demonstrated a high test-retest reliability (r(27) = 0.83, P < .001) and enabled discrimination between normosmia and children with congenital anosmia with a sensitivity of 100% and specificity of 86%.ConclusionsThe U-Sniff is a valid and reliable method of testing olfaction in children and can be used internationally.
3.	Thunell, Evelina, et al. (author) Effects of COVID-19 on the Human Central Olfactory System : A Natural Pre-Post Experiment 2022 In: American Journal of Neuroradiology. - 0195-6108 .- 1936-959X. ; 43:12, s. 1777-1783 Journal article (peer-reviewed)abstract BACKGROUND AND PURPOSE: Reduced olfactory function is the symptom with the highest prevalence in coronavirus disease 2019 (COVID-19) with nearly 70% of infected individuals experiencing partial or total loss of their sense of smell at some point during the disease. The exact cause is not known, but beyond peripheral damage, studies have demonstrated insults to both the olfactory bulb and central olfactory brain areas. However, these studies often lack both baseline pre-COVID-19 assessments and control groups, and the effects could, therefore, simply reflect pre-existing risk factors.MATERIALS AND METHODS: Shortly before the COVID-19 outbreak, we completed an olfactory-focused study, which included structural MR brain images and a full clinical olfactory test. Opportunistically, we invited participants back 1 year later, including 9 participants who had experienced mild-to-moderate COVID-19 (C19+) and 12 who had not (C19−), creating a natural pre-post experiment with a control group.RESULTS: Despite C19+ participants reporting subjective olfactory dysfunction, few showed signs of objectively altered function. Critically, all except 1 individual in the C19+ group had reduced olfactory bulb volume (average reduction, 14.3%), but this did not amount to a significant statistical difference compared with the control group (2.3%) using inference statistics. We found no morphologic differences in olfactory brain areas but stronger functional connectivity between olfactory brain areas in the C19+ group at the postmeasure.CONCLUSIONS: Our data suggest that COVID-19 might cause long-term reduction in olfactory bulb volume and altered functional connectivity but with no discernible morphologic differences in cerebral olfactory regions.
4.	Arshamian, Artin, et al. (author) A mammalian blood odor component serves as an approach-avoidance cue across phylum border - from flies to humans 2017 In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7 Journal article (peer-reviewed)abstract Chemosignals are used by predators to localize prey and by prey to avoid predators. These cues vary between species, but the odor of blood seems to be an exception and suggests the presence of an evolutionarily conserved chemosensory cue within the blood odor mixture. A blood odor component, E2D, has been shown to trigger approach responses identical to those triggered by the full blood odor in mammalian carnivores and as such, is a key candidate as a food/alarm cue in blood. Using a multidisciplinary approach, we demonstrate that E2D holds the dual function of affecting both approach and avoidance behavior in a predator-prey predicted manner. E2D evokes approach responses in two taxonomically distant blood-seeking predators, Stable fly and Wolf, while evoking avoidance responses in the prey species Mouse. We extend this by demonstrating that this chemical cue is preserved in humans as well; E2D induces postural avoidance, increases physiological arousal, and enhances visual perception of affective stimuli. This is the first demonstration of a single chemical cue with the dual function of guiding both approach and avoidance in a predator-prey predicted manner across taxonomically distant species, as well as the first known chemosignal that affects both human and non-human animals alike.
5.	Arshamian, Artin, et al. (author) Respiration Modulates Olfactory Memory Consolidation in Humans 2018 In: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 38:48, s. 10286-10294 Journal article (peer-reviewed)abstract In mammals respiratory-locked hippocampal rhythms are implicated in the scaffolding and transfer of information between sensory and memory networks. These oscillations are entrained by nasal respiration and driven by the olfactory bulb. They then travel to the piriform cortex where they propagate further downstream to the hippocampus and modulate neural processes critical for memory formation. In humans, bypassing nasal airflow through mouth-breathing abolishes these rhythms and impacts encoding as well as recognition processes thereby reducing memory performance. It has been hypothesized that similar behavior should be observed for the consolidation process, the stage between encoding and recognition, were memory is reactivated and strengthened. However, direct evidence for such an effect is lacking in human and nonhuman animals. Here we tested this hypothesis by examining the effect of respiration on consolidation of episodic odor memory. In two separate sessions, female and male participants encoded odors followed by a 1 h awake resting consolidation phase where they either breathed solely through their nose or mouth. Immediately after the consolidation phase, memory for odors was tested. Recognition memory significantly increased during nasal respiration compared with mouth respiration during consolidation. These results provide the first evidence that respiration directly impacts consolidation of episodic events, and lends further support to the notion that core cognitive functions are modulated by the respiratory cycle.
6.	Arshamian, Artin, et al. (author) The perception of odor pleasantness is shared across cultures 2022 In: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 32:9, s. 2061-2066, e1-e3 Journal article (peer-reviewed)abstract Humans share sensory systems with a common anatomical blueprint, but individual sensory experience nevertheless varies. In olfaction, it is not known to what degree sensory perception, particularly the perception of odor pleasantness, is founded on universal principles dictated by culture or merely a matter of personal taste. To address this, we asked 225 individuals from 9 diverse nonwestern cultures—hunter-gatherer to urban dwelling—to rank the monomolecular odorants from most to least pleasant. Contrary to expectations, culture explained only 6% of the variance in pleasantness rankings, whereas individual variability or personal taste explained 54%. Importantly, there was substantial global consistency, with molecular identity explaining 41% of the variance in odor pleasantness rankings. Critically, these universal rankings were predicted by the physicochemical properties of out-of-sample molecules and out-of-sample pleasantness ratings given by a tenth group of western urban participants. Taken together, this shows human olfactory perception is strongly constrained by universal principles.
7.	Boyle, Julie A., et al. (author) The Human Brain Distinguishes between Single Odorants and Binary Mixtures 2009 In: Cerebral Cortex. - : Oxford University Press (OUP). - 1047-3211 .- 1460-2199. ; 19:1, s. 66-71 Journal article (peer-reviewed)abstract Single odors are processed differently from odor mixtures in the cortex of rodents. We investigated whether single and binary odor mixtures activate different regions also in the human brain. We analyzed data from positron emission tomography scans using pyridine, citral, and 5 mixtures of pyridine and citral in proportions varying from 10/90 to 90/10, with 50/50 being the most impure. Comparing mixtures with single odorants gave activation in the left cingulate and right parietal and superior frontal cortices and bilateral activation in the anterior and lateral orbitofrontal cortices. We also found that brain activity in the lateral orbitofrontal cortex (OFC) increased with odorant impurity, whereas the anterior OFC was activated for binary odor mixtures and deactivated for single components. We conclude that binary odor mixtures and their individual components are processed differently by the human brain. The lateral portion of the OFC responds to mixture impurity in a graded fashion, whereas the anterior portion acts like an on-off detector of odor mixtures.
8.	Fondberg, Robin, et al. (author) Multisensory flavor perception : The relationship between congruency, pleasantness, and odor referral to the mouth 2018 In: Appetite. - : Elsevier BV. - 0195-6663 .- 1095-8304. ; 125, s. 244-252 Journal article (peer-reviewed)abstract Our hedonic response to a food is determined by its flavor, an inherently multisensory experience that extends beyond the mere addition of its odor and taste. While congruency is known to be important for multisensory processes in general, little is known about its specific role in flavor processing. The aim of the present study was to delineate the effects of odor-taste congruency on two central aspects of flavor: odor referral (or mislocalization) to the mouth, and pleasantness. We further aimed to test whether an eventual effect on pleasantness was mediated by odor referral. Aqueous solutions containing odors and tastes were prepared to create food-like stimuli with varying degrees of congruency, ranging from maximally incongruent to maximally congruent in nine steps. Thirty participants reported where they perceived the odors, and how much they liked the solutions. Congruency had a positive linear effect both on odor referral to the oral cavity and on pleasantness. However, the effect of congruency on pleasantness was not mediated by odor referral. These results indicate that as an odor-taste mixture approximates a mental representation of a familiar food, its components are increasingly merged into one perceptual object sensed in the mouth. In parallel, the mixture is evaluated as increasingly pleasant, which promotes consumption of familiar foods that have been determined through experience to be non-toxic. While the modulatory role of congruency on pleasantness and odor referral was confirmed, our results also indicate that these effects arise through distinct perceptual mechanisms.
9.	Fondberg, Robin, et al. (author) Odor-Taste Interactions in Food Perception : Exposure Protocol Shows No Effects of Associative Learning 2021 In: Chemical Senses. - : Oxford University Press (OUP). - 0379-864X .- 1464-3553. ; 46, s. 1-14 Journal article (peer-reviewed)abstract Repeated exposure can change the perceptual and hedonic features of flavor. Associative learning during which a flavor's odor component is affected by co-exposure with taste is thought to be central in this process. However, changes can also arise due to exposure to the odor in itself. The aim of this study was to dissociate effects of associative learning from effects of exposure without taste by repeatedly presenting one odor together with sucrose and a second odor alone. Sixty individuals attended two testing sessions separated by a 5-day Exposure Phase during which the stimuli were presented as flavorants in chewing gums that were chewed three times daily. Ratings of odor sweetness, odor pleasantness, odor intensity enhancement by taste, and odor referral to the mouth were collected at both sessions. Consistent with the notion that food preferences are modulated by exposure, odor pleasantness increased between the sessions independently of whether the odor (basil or orange flower) had been presented with or without sucrose. However, we found no evidence of associative learning in any of the tasks. In addition, exploratory equivalence tests suggested that these effects were either absent or insignificant in magnitude. Taken together, our results suggest that the hypothesized effects of associative learning are either smaller than previously thought or highly dependent on the experimental setting. Future studies are needed to evaluate the relative support for these explanations and, if experimental conditions can be identified that reliably produce such effects, to identify factors that regulate the formation of new odor-taste associations.
10.	Gerhardsson, Andreas, et al. (author) Does insufficient sleep affect how you learn from reward or punishment? Reinforcement learning after 2 nights of sleep restriction 2021 In: Journal of Sleep Research. - : Wiley. - 0962-1105 .- 1365-2869. ; 30:4 Journal article (peer-reviewed)abstract To learn from feedback (trial and error) is essential for all species. Insufficient sleep has been found to reduce the sensitivity to feedback as well as increase reward sensitivity. To determine whether insufficient sleep alters learning from positive and negative feedback, healthy participants (n = 32, mean age 29.0 years, 18 women) were tested once after normal sleep (8 hr time in bed for 2 nights) and once after 2 nights of sleep restriction (4 hr/night) on a probabilistic selection task where learning behaviour was evaluated in three ways: as generalised learning, short-term win-stay/lose-shift learning strategies, and trial-by-trial learning rate. Sleep restriction did not alter the sensitivity to either positive or negative feedback on generalised learning. Also, short-term win-stay/lose-shift strategies were not affected by sleep restriction. Similarly, results from computational models that assess the trial-by-trial update of stimuli value demonstrated no difference between sleep conditions after the first block. However, a slower learning rate from negative feedback when evaluating all learning blocks was found after sleep restriction. Despite a marked increase in sleepiness and slowed learning rate for negative feedback, sleep restriction did not appear to alter strategies and generalisation of learning from positive or negative feedback.
11.	Gordon, Amy R., et al. (author) Detection of Inflammation via Volatile Cues in Human Urine 2018 In: Chemical Senses. - : Oxford University Press (OUP). - 0379-864X .- 1464-3553. ; 43:9, s. 711-719 Journal article (peer-reviewed)abstract Contagious disease is a major threat to survival, and the cost of relying on the immune system to defeat pathogens is high; therefore, behavioral avoidance of contagious individuals is arguably an adaptive strategy. Animal findings demonstrate the ability to detect and avoid sick individuals by the aid of olfactory cues, and a recent study indicated that human axillary odor also becomes more aversive as a function of immune activation. By injecting healthy human participants with lipopolysaccharide (0.6 ng/kg body weight) to experimentally induce inflammation, this study demonstrates that natural daily rhythms of urine odor-its perceived dimensions and volatile profile-are altered within hours of inflammation onset. Whereas healthy human urine decreases in averseness over the course of a single day, inflammation interrupts this process and results in an increased urine odor averseness and an altered volatile composition. These results support the notion that subtle and early cues of sickness may be detected and avoided, thereby complementing the immune system in its role of keeping us alive and healthy.
12.	Gordon, Amy R., et al. (author) Human scent as a first-line defense against disease 2023 In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1 Journal article (peer-reviewed)abstract Individuals may have a different body odor, when they are sick compared to healthy. In the non-human animal literature, olfactory cues have been shown to predict avoidance of sick individuals. We tested whether the mere experimental activation of the innate immune system in healthy human individuals can make an individuals' body odor be perceived as more aversive (intense, unpleasant, and disgusting). Following an endotoxin injection (lipopolysaccharide; 0.6 ng/kg) that creates a transient systemic inflammation, individuals smelled more unpleasant compared to a placebo group (saline injection). Behavioral and chemical analyses of the body odor samples suggest that the volatile components of samples from sick individuals changed qualitatively rather than quantitatively. Our findings support the hypothesis that odor cues of inflammation in axillary sweat are detectable just a few hours after experimental activation of the innate immune system. As such, they may trigger behavioral avoidance, hence constituting a first line of defense against pathogens of infected conspecifics.
13.	Gordon, Amy R., et al. (author) Partner’s body odor lowers stress symptoms 2016 Conference paper (other academic/artistic)
14.	Gordon, Amy R., et al. (author) The scent of disease 2015 In: Chemical Senses. - : Oxford University Press (OUP). - 0379-864X .- 1464-3553. ; 40:3, s. 254-254 Journal article (peer-reviewed)abstract Ability to detect diseases in conspecifics would be advantageous for the individual. In line with this, rodents avoid body odors of infected individuals. Two studies (Olsson et al. 20014; in prep.) indicated that this is possible by way of human smell and human observers. T-shirts from donors (worn for 4 hours) that had received an injection of endotoxin [0.8ng lipopolysaccharide (LPS) / kg body weight], which causes systemic inflammation, smelled more unpleasant, intense, and sick than shirts from donors that had received a placebo (Saline) injection. GC/MS analysis of the shirts suggested that the change of body odor was not due to a general increase of odorous compounds in the “sick shirts” compared to “placebo shirts” but rather to a qualitative change. Study 2 (ongoing) further investigated the nature of this perception. In a first experiment, we compared the body odor of 30 endotoxin (0.6ng LPS / kg body weight) and 21 placebo (Saline) donors. Again, body odors were sampled during 4 hours using T-shirts. Observers then smelled the shirts and rated intensity, pleasantness, and disgust. In a second experiment, urine from these donors were collected and was investigated in the same way with subjective ratings. Altogether the data suggest that systemic inflammation makes body odors more aversive within a few hours.
15.	Granqvist, Pehr, et al. (author) The scent of security : Odor of romantic partner alters subjective discomfort and autonomic stress responses in an adult attachment-dependent manner 2019 In: Physiology and Behavior. - : Elsevier BV. - 0031-9384 .- 1873-507X. ; 198, s. 144-150 Journal article (peer-reviewed)abstract When in a stressful situation, access to adult attachment figures (e.g., romantic partners) is an important means by which adults regulate stress responses. The practice of smelling a partner's worn garment is reported as a self-treatment against stress. Here, we experimentally determined whether exposure to a partner's body odor attenuates adults' subjective discomfort and psychophysiological responses, and whether such effects are qualified by adult attachment security. In a blocked design, participants (N = 34) were presented with their partner's body odor, their own body odor, the odor of a clean t-shirt and rose odor, while exposed to weak electric shocks to induce discomfort and stress responses. Results showed that partner body odor reduces subjective discomfort during a stressful event, as compared with the odor of oneself. Also, highly secure participants had attenuated skin conductance when exposed to partner odor. We conclude that partner odor is a scent of security, especially for attachment-secure adults.
16.	Hedblom, Marcus, et al. (author) Reduction of physiological stress by urban green space in a multisensory virtual experiment 2019 In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9 Journal article (peer-reviewed)abstract Although stress is an increasing global health problem in cities, urban green spaces can provide health benefits. There is, however, a lack of understanding of the link between physiological mechanisms and qualities of urban green spaces. Here, we compare the effects of visual stimuli (360 degree virtual photos of an urban environment, forest, and park) to the effects of congruent olfactory stimuli (nature and city odours) and auditory stimuli (bird songs and noise) on physiological stress recovery. Participants (N = 154) were pseudo-randomised into participating in one of the three environments and subsequently exposed to stress (operationalised by skin conductance levels). The park and forest, but not the urban area, provided significant stress reduction. High pleasantness ratings of the environment were linked to low physiological stress responses for olfactory and to some extent for auditory, but not for visual stimuli. This result indicates that olfactory stimuli may be better at facilitating stress reduction than visual stimuli. Currently, urban planners prioritise visual stimuli when planning open green spaces, but urban planners should also consider multisensory qualities.
17.	Hedblom, Marcus, et al. (author) Sounds of Nature in the City: No Evidence of Bird Song Improving Stress Recovery 2019 In: International Journal of Environmental Research and Public Health. - : MDPI AG. - 1660-4601 .- 1661-7827. ; 16:8 Journal article (peer-reviewed)abstract Noise from city traffic is one of the most significant environmental stressors. Natural soundscapes, such as bird songs, have been suggested to potentially mitigate or mask noise. All previous studies on masking noise use self-evaluation data rather than physiological data. In this study, while respondents (n = 117) watched a 360 degrees virtual reality (VR) photograph of a park, they were exposed to different soundscapes and mild electrical shocks. The soundscapesbird song, bird song and traffic noise, and traffic noisewere played during a 10 min recovery period while their skin conductance levels were assessed as a measure of arousal/stress. No significant difference in stress recovery was found between the soundscapes although a tendency for less stress in bird song and more stress in traffic noise was noted. All three soundscapes, however, significantly reduced stress. This result could be attributed to the stress-reducing effect of the visual VR environment, to the noise levels being higher than 47 dBA (a level known to make masking ineffective), or to the respondents finding bird songs stressful. Reduction of stress in cities using masking with natural sounds requires further studies with not only larger samples but also sufficient methods to detect potential sex differences.
18.	Iravani, Behzad, et al. (author) A non-invasive olfactory bulb measure dissociates Parkinson's patients from healthy controls and discloses disease duration 2021 In: npj Parkinson's Disease. - : Springer Science and Business Media LLC. - 2373-8057. ; 7:1 Journal article (peer-reviewed)abstract Olfactory dysfunction is a prevalent non-motor symptom of Parkinson’s disease (PD). This dysfunction is a result of neurodegeneration within the olfactory bulb (OB), the first processing area of the central olfactory system, and commonly precedes the characteristic motor symptoms in PD by several years. Functional measurements of the OB could therefore potentially be used as an early biomarker for PD. Here, we used a non-invasive method, so-called electrobulbogram (EBG), to measure OB function in PD and age-matched healthy controls to assess whether EBG measures can dissociate PDs from controls. We estimated the spectrogram of the EBG signal during exposure to odor in PD (n = 20) and age-matched controls (n = 18) as well as identified differentiating patterns of odor-related synchronization in the gamma, beta, and theta frequency bands. Moreover, we assessed if these PD-EBG components could dissociate PD from control as well as their relationship with PD characteristics. We identified six EBG components during the initial and later stages of odor processing which dissociated PD from controls with 90% sensitivity and 100% specificity with links to PD characteristics. These PD-EBG components were related to medication, disease duration, and severity, as well as clinical odor identification performance. These findings support using EBG as a tool to experimentally assess PD interventions, potentially aid diagnosis, and the potential development of EBG into an early biomarker for PD.
19.	Iravani, Behzad, et al. (author) Acquired olfactory loss alters functional connectivity and morphology 2021 In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1 Journal article (peer-reviewed)abstract Removing function from a developed and functional sensory system is known to alter both cerebral morphology and functional connections. To date, a majority of studies assessing sensory-dependent plasticity have focused on effects from either early onset or long-term sensory loss and little is known how the recent sensory loss affects the human brain. With the aim of determining how recent sensory loss affects cerebral morphology and functional connectivity, we assessed differences between individuals with acquired olfactory loss (duration 7-36 months) and matched healthy controls in their grey matter volume, using multivariate pattern analyses, and functional connectivity, using dynamic connectivity analyses, within and from the olfactory cortex. Our results demonstrate that acquired olfactory loss is associated with altered grey matter volume in, among others, posterior piriform cortex, a core olfactory processing area, as well as the inferior frontal gyrus and angular gyrus. In addition, compared to controls, individuals with acquired anosmia displayed significantly stronger dynamic functional connectivity from the posterior piriform cortex to, among others, the angular gyrus, a known multisensory integration area. When assessing differences in dynamic functional connectivity from the angular gyrus, individuals with acquired anosmia had stronger connectivity from the angular gyrus to areas primary responsible for basic visual processing. These results demonstrate that recently acquired sensory loss is associated with both changed cerebral morphology within core olfactory areas and increase dynamic functional connectivity from olfactory cortex to cerebral areas processing multisensory integration.
20.	Iravani, Behzad, et al. (author) Loss of olfactory sensitivity is an early and reliable marker for COVID-19 2022 In: Chemical Senses. - : Oxford University Press (OUP). - 0379-864X .- 1464-3553. ; 47 Journal article (peer-reviewed)abstract Detection of early and reliable symptoms is important in relation to limiting the spread of an infectious disease. For COVID-19, the most specific symptom is either losing or experiencing reduced olfactory functions. Anecdotal evidence suggests that olfactory dysfunction is also one of the earlier symptoms of COVID-19, but objective measures supporting this notion are currently missing. To determine whether olfactory loss is an early sign of COVID-19, we assessed available longitudinal data from a web-based interface enabling individuals to test their sense of smell by rating the intensity of selected household odors. Individuals continuously used the interface to assess their olfactory functions and at each login, in addition to odor ratings, recorded their symptoms and results from potential COVID-19 test. A total of 205 COVID-19-positive individuals and 156 pseudo-randomly matched control individuals lacking positive test provided longitudinal data which enabled us to assess olfactory functions in relation to their test result date. We found that odor intensity ratings started to decline in the COVID-19 group as early as 6 days prior to the test result date (±1.4 days). Symptoms, such as sore throat, aches, and runny nose appear around the same point in time; however, with a lower predictability of a COVID-19 diagnosis. Our results suggest that olfactory sensitivity loss is an early symptom but does not appear before other related COVID-19 symptoms. Olfactory loss is, however, more predictive of a COVID-19 diagnosis than other early symptoms.
21.	Iravani, Behzad, et al. (author) Non-invasive recording from the human olfactory bulb 2020 In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11:1 Journal article (peer-reviewed)abstract Measures of neural processing can be obtained non-invasively from all areas of the human brain but one, the olfactory bulb. Here, the authors show that signals obtained from EEG electrodes at the nasal bridge represent responses from the human olfactory bulb, the so-called Electrobulbogram. Current non-invasive neuroimaging methods can assess neural activity in all areas of the human brain but the olfactory bulb (OB). The OB has been suggested to fulfill a role comparable to that of V1 and the thalamus in the visual system and have been closely linked to a wide range of olfactory tasks and neuropathologies. Here we present a method for non-invasive recording of signals from the human OB with millisecond precision. We demonstrate that signals obtained via recordings from EEG electrodes at the nasal bridge represent responses from the human olfactory bulb - recordings we term Electrobulbogram (EBG). The EBG will aid future olfactory-related translational work but can also potentially be implemented as an everyday clinical tool to detect pathology-related changes in human central olfactory processing in neurodegenerative diseases. In conclusion, the EBG is localized to the OB, is reliable, and follows response patterns demonstrated in non-human animal models.
22.	Iravani, Behzad, et al. (author) Odor identity can be extracted from the reciprocal connectivity between olfactory bulb and piriform cortex in humans 2021 In: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 237 Journal article (peer-reviewed)abstract Neuronal oscillations route external and internal information across brain regions. In the olfactory system, the two central nodes -the olfactory bulb (OB) and the piriform cortex (PC) -communicate with each other via neural oscillations to shape the olfactory percept. Communication between these nodes have been well characterized in non-human animals but less is known about their role in the human olfactory system. Using a recently developed and validated EEG-based method to extract signals from the OB and PC sources, we show in healthy human participants that there is a bottom-up information flow from the OB to the PC in the beta and gamma frequency bands, while top-down information from the PC to the OB is facilitated by delta and theta oscillations. Importantly, we demonstrate that there was enough information to decipher odor identity above chance from the low gamma in the OB-PC oscillatory circuit as early as 100 ms after odor onset. These data further our understanding of the critical role of bidirectional information flow in human sensory systems to produce perception. However, future studies are needed to determine what specific odor information is extracted and communicated in the information exchange.
23.	Iravani, Behzad, et al. (author) Relationship Between Odor Intensity Estimates and COVID-19 Prevalence Prediction in a Swedish Population 2020 In: Chemical Senses. - : Oxford University Press (OUP). - 0379-864X .- 1464-3553. ; 45:6, s. 449-456 Journal article (peer-reviewed)abstract In response to the coronavirus disease 2019 (COVID-19) pandemic, countries have implemented various strategies to reduce and slow the spread of the disease in the general population. For countries that have implemented restrictions on its population in a stepwise manner, monitoring of COVID-19 prevalence is of importance to guide the decision on when to impose new, or when to abolish old, restrictions. We are here determining whether measures of odor intensity in a large sample can serve as one such measure. Online measures of how intense common household odors are perceived and symptoms of COVID-19 were collected from 2440 Swedes. Average odor intensity ratings were then compared to predicted COVID-19 population prevalence over time in the Swedish population and were found to closely track each other (r = -0.83). Moreover, we found that there was a large difference in rated intensity between individuals with and without COVID-19 symptoms and the number of symptoms was related to odor intensity ratings. Finally, we found that individuals progressing from reporting no symptoms to subsequently reporting COVID-19 symptoms demonstrated a large drop in olfactory performance. These data suggest that measures of odor intensity, if obtained in a large and representative sample, can be used as an indicator of COVID-19 disease in the general population. Importantly, this simple measure could easily be implemented in countries without widespread access to COVID-19 testing or implemented as a fast early response before widespread testing can be facilitated.
24.	Iravani, Behzad, et al. (author) The human olfactory bulb processes odor valence representation and cues motor avoidance behavior 2021 In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 118:42 Journal article (peer-reviewed)abstract Determining the valence of an odor to guide rapid approach–avoidance behavior is thought to be one of the core tasks of the olfactory system, and yet little is known of the initial neural mechanisms supporting this process or of its subsequent behavioral manifestation in humans. In two experiments, we measured the functional processing of odor valence perception in the human olfactory bulb (OB)—the first processing stage of the olfactory system—using a noninvasive method as well as assessed the subsequent motor avoidance response. We demonstrate that odor valence perception is associated with both gamma and beta activity in the human OB. Moreover, we show that negative, but not positive, odors initiate an early beta response in the OB, a response that is linked to a preparatory neural motor response in the motor cortex. Finally, in a separate experiment, we show that negative odors trigger a full-body motor avoidance response, manifested as a rapid leaning away from the odor, within the time period predicted by the OB results. Taken together, these results demonstrate that the human OB processes odor valence in a sequential manner in both the gamma and beta frequency bands and suggest that rapid processing of unpleasant odors in the OB might underlie rapid approach–avoidance decisions.
25.	Juran, Stephanie Anja, et al. (author) Disgusting odors trigger the oral immune system 2023 In: Evolution, Medicine, and Public Health. - : Oxford University Press. - 2050-6201. ; 11:1, s. 8-17 Journal article (peer-reviewed)abstract Recent research has characterized the behavioral defense against disease. In particular the detection of sickness cues, the adaptive reactions (e.g. avoidance) to these cues and the mediating role of disgust have been the focus. A presumably important but less investigated part of a behavioral defense is the immune system response of the observer of sickness cues. Odors are intimately connected to disease and disgust, and research has shown how olfaction conveys sickness cues in both animals and humans. This study aims to test whether odorous sickness cues (i.e. disgusting odors) can trigger a preparatory immune response in humans. We show that subjective and objective disgust measures, as well as TNFα levels in saliva increased immediately after exposure to disgusting odors in a sample of 36 individuals. Altogether, these results suggest a collaboration between behavioral mechanisms of pathogen avoidance in olfaction, mediated by the emotion of disgust, and mechanisms of pathogen elimination facilitated by inflammatory mediators.Disgusting stimuli are associated with an increased risk of infection. We here test whether disgusting odors, can trigger an immune response in the oral cavity. The results indicate an increase level of TNFα in the saliva. This supports that disease cues can trigger a preparatory response in the oral cavity.

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