Human Olfaction without Apparent Olfactory Bulbs

Weiss, Tali; Soroka, Timna; Gorodisky, Lior; Shushan, Sagit; Snitz, Kobi; Weissgross, Reut; Furman‐Haran, Edna; Dhollander, Thijs; Sobel, Noam

doi:10.1016/j.neuron.2019.10.006

Cited by 48 publications

(45 citation statements)

References 68 publications

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“…Early olfactory deficits are consistent with the olfactory vector hypothesis for PD pathogenesis and the caudo-rostral spread of LB pathology (113)(114)(115). It is interesting however, that some individuals with normal olfaction lack olfactory bulbs (125). This suggests that the establishment and maintenance of olfactory circuits has considerable functional plasticity.…”

Section: How Is Od Related To Disease Onset and Progression?supporting

confidence: 66%

Olfactory Dysfunction in Familial and Sporadic Parkinson's Disease

Chase

Μarkopoulou

2020

Front. Neurol.

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This minireview discusses our current understanding of the olfactory dysfunction that is frequently observed in sporadic and familial forms of Parkinson's disease and parkinsonian syndromes. We review the salient characteristics of olfactory dysfunction in these conditions, discussing its prevalence and characteristics, how neuronal processes and circuits are altered in Parkinson's disease, and what is assessed by clinically used measures of olfactory function. We highlight how studies of monogenic Parkinson's disease and investigations in ethnically diverse populations have contributed to understanding the mechanisms underlying olfactory dysfunction. Furthermore, we discuss how imaging and system-level approaches have been used to understand the pathogenesis of olfactory dysfunction. We discuss the challenging, remaining gaps in understanding the basis of olfactory dysfunction in neurodegeneration. We propose that insights could be obtained by following longitudinal cohorts with familial forms of Parkinson's disease using a combination of approaches: a multifaceted longitudinal assessment of olfactory function during disease progression is essential to identify not only how dysfunction arises, but also to address its relationship to motor and non-motor Parkinson's disease symptoms. An assessment of cohorts having monogenic forms of Parkinson's disease, available within the Genetic Epidemiology of Parkinson's Disease (GEoPD), as well as other international consortia, will have heuristic value in addressing the complexity of olfactory dysfunction in the context of the neurodegenerative process. This will inform our understanding of Parkinson's disease as a multisystem disorder and facilitate the more effective use of olfactory dysfunction assessment in identifying prodromal Parkinson's disease and understanding disease progression.

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Section: How Is Od Related To Disease Onset and Progression?supporting

confidence: 66%

Olfactory Dysfunction in Familial and Sporadic Parkinson's Disease

Chase

Μarkopoulou

2020

Front. Neurol.

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“…Like the aetiologies of smell loss, both central and peripheral mechanisms have been proposed 21 and can broadly be thought of as the central theory, the ephaptic theory and the mis-wiring theory. Although there is now some doubt about the role of the bulb in olfactory identification 22 , these theories take the standard model of glomerular activation pattern within the olfactory bulb as the motif of recognition within the CNS.…”

Section: Discussionmentioning

confidence: 99%

Molecular Mechanism of Parosmia

Parker

Kelly²,

Gane

2021

Preprint

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The molecular stimuli that trigger parosmia have been identified. Parosmia is a debilitating disease in which familiar smells become distorted and unpleasant. Often a result of post infectious smell loss, incidences are increasing as the number of COVID-19 cases escalates worldwide. Little is understood of its pathophysiology, but the prevailing hypothesis for the underlying mechanism is a mis-wiring of olfactory sensory neurons. We identified 15 different molecular triggers in coffee using GC-Olfactometry as a relatively rapid screening tool for assessment of both quantitative olfactory loss and parosmia. This provides evidence for peripheral causation, but places constraints on the mis-wiring theory.

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“…Another, albeit highly speculative, possibility could be that smells might be differently processed in individuals with obesity. Following the observation of Weiss et al (2020) that people without apparent OBs can still smell, one can speculate that other structures in the brain might take over the processing of olfactory information by the formation of a glomerular space somewhere else in the cortex. In this respect, we assume that although the OB volume might be lower in our obese sample, the olfactory ability might be preserved by other structures.…”

Section: Discussionmentioning

confidence: 99%

Reduced Olfactory Bulb Volume in Obesity and Its Relation to Metabolic Health Status

Poessel

Breuer

Joshi³

et al. 2020

Front. Hum. Neurosci.

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Smell perception plays an important role in eating behavior and might be involved in body weight gain. Since a body of literature implies that olfactory perception and function is hampered in obesity, we here investigate neuroanatomical correlates of this phenomenon. We assessed olfactory bulb (OB) volume with magnetic resonance imaging in 67 healthy participants with a body mass index (BMI) from 18.9 to 45.4 kg/m2 (mean = 28.58 ± 6.64). Moreover, we obtained psychophysiological data on olfactory ability (Sniffin’ Sticks, Food associated odor test) and self-report measurements on eating behavior. Additionally, we collected parameters associated with metabolic health in obesity (waist-hip ratio, waist-height ratio, leptin levels, body fat percentage, fat mass index, insulin resistance) to investigate recently proposed mechanistic explanatory models of why olfaction may be altered in obesity. We showed that OB volume was significantly lower in participants with obesity when compared to those of normal weight. Moreover, we found weak to moderate negative correlations between OB volume and BMI and related measures of metabolic health, especially leptin, body fat percentage, waist-height ratio and insulin resistance. However, neither OB volume nor BMI were related to olfactory function in our young and healthy sample. Nevertheless, our results provide first indications that obesity is associated with brain anatomical changes in the OBs.

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Human Olfaction without Apparent Olfactory Bulbs

Abstract: Highlights d Humans can have normal olfaction without apparent olfactory bulbs d Olfaction without apparent bulbs is seen in 0.6% of women, but not in men d Olfaction without apparent bulbs is associated with lefthandedness

Cited by 48 publications

References 68 publications

Olfactory Dysfunction in Familial and Sporadic Parkinson's Disease

Olfactory Dysfunction in Familial and Sporadic Parkinson's Disease

Molecular Mechanism of Parosmia

Reduced Olfactory Bulb Volume in Obesity and Its Relation to Metabolic Health Status

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