Biology of Olfactory Disorders

Dear Colleagues,

The study of the olfactory system, and related chemical senses, is probably the most intriguing because of its ancestral biological role. In fact, the mechanism of reproduction is based on a chemoreceptive process in which sperm, with the same olfactory receptors present in the nose, 'smell' the egg and follow its released chemical trail. This suggests its importance in all aspects of life, from food preference to the choice of environment and partner. Consequently, the impairment of the sense of smell and related chemical senses is of dramatic importance for health. Recently, we have realised that smell is often an early marker of infection, as in the case of COVID-19, or pathology, as in neurodegenerative diseases such as Parkinson's and Alzheimer's. In addition, in endocrine dysfunctions such as genetic Kallmann syndrome, characterised by hypogonadotropic hypogonadism, anosmia or dysosmia is a hallmark. Similarly, in emerging environmental diseases, such as multiple chemical sensitivity, hyperosmia is a signature symptom. Furthermore, in courtship, volatile chemosignals prevent inbreeding in humans (human leukocyte antigen, HLA). Other phenomena are presbyosmia, i.e., the change in olfactory phenotype from young to mature or old with age; phantosmia or olfactory hallucination and cacosmia or unpleasant perception. Scientific advances in the sense of smell research have progressed enormously in recent decades, but there are still many aspects to be investigated. For example, the mechanisms of olfactory perception are still being debated, and it is still unknown how we store memories of smells and tastes experienced many years ago, considering that olfactory neurons are regularly replaced throughout life. For that purpose, olfactometric techniques are of crucial importance ranging from psychophysical tests to objective tests such as electrophysiological measurements (olfactory event-related potential (OERP), olfactory electroencephalogram (OEEG), electro-olfactogram (EOG)); imaging techniques (olfactory functional magnetic resonance imaging (o-fMRI), olfactory positron emission tomography (o-PET)); and advanced techniques, such as the Volabolomic approach (olfactory real-time VOCs test (ORT-VOCs test)) have been introduced to obtain more information on olfactory function and the different aetiologies of sensory impairment. Hence, this Special Issue is open to the publication of interesting or innovative original work from clinical practice and research. This Special Issue aims to delve into various topics related to our chemical senses and to capture the most interesting developments in the field.

Dr. Andrea Mazzatenta
Guest Editor

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• smell impairment
• taste impairments
• olfactometry
• olfactory event-related potential
• anosmia–hyposmia–dysosmia
• presbiosmia–phantosmia–cacosmia
• COVID-19
• neurodegenerative disease
• Kallmann syndrome
• multiple chemical sensitivity