Recent anecdotal and scientific reports have provided evidence of a link between COVID-19 and chemosensory impairments, such as anosmia. However, these reports have downplayed or failed to distinguish potential effects on taste, ignored chemesthesis, and generally lacked quantitative measurements. Here, we report the development, implementation, and initial results of a multilingual, international questionnaire to assess self-reported quantity and quality of perception in 3 distinct chemosensory modalities (smell, taste, and chemesthesis) before and during COVID-19. In the first 11 days after questionnaire launch, 4039 participants (2913 women, 1118 men, and 8 others, aged 19–79) reported a COVID-19 diagnosis either via laboratory tests or clinical assessment. Importantly, smell, taste, and chemesthetic function were each significantly reduced compared to their status before the disease. Difference scores (maximum possible change ±100) revealed a mean reduction of smell (−79.7 ± 28.7, mean ± standard deviation), taste (−69.0 ± 32.6), and chemesthetic (−37.3 ± 36.2) function during COVID-19. Qualitative changes in olfactory ability (parosmia and phantosmia) were relatively rare and correlated with smell loss. Importantly, perceived nasal obstruction did not account for smell loss. Furthermore, chemosensory impairments were similar between participants in the laboratory test and clinical assessment groups. These results show that COVID-19-associated chemosensory impairment is not limited to smell but also affects taste and chemesthesis. The multimodal impact of COVID-19 and the lack of perceived nasal obstruction suggest that severe acute respiratory syndrome coronavirus strain 2 (SARS-CoV-2) infection may disrupt sensory-neural mechanisms.

In recent years, considerable progress has been achieved in the comprehension of the profound effects of pheromones on reproductive physiology and behavior. Pheromones have been classified as molecules released by individuals and responsible for the elicitation of specific behavioral expressions in members of the same species. These signaling molecules, often chemically unrelated, are contained in body fluids like urine, sweat, specialized exocrine glands, and mucous secretions of genitals. The standard view of pheromone sensing was based on the assumption that most mammals have two separated olfactory systems with different functional roles: the main olfactory system for recognizing conventional odorant molecules and the vomeronasal system specifically dedicated to the detection of pheromones. However, recent studies have reexamined this traditional interpretation showing that both the main olfactory and the vomeronasal systems are actively involved in pheromonal communication. The current knowledge on the behavioral, physiological, and molecular aspects of pheromone detection in mammals is discussed in this review.

Sensory transduction shares common features in widely different sensory modalities. The purpose of this article is to examine the similarities and differences in the underlying mechanisms of transduction in the sensory receptor cells for vision, olfaction, and hearing. One of the major differences between the systems relates to the nature of the stimulus. In both the visual and olfactory systems a quantal mechanism of detection is possible, because the absorption of a photon or the binding of an odorant molecule provides an energy change significantly greater than the thermal noise in the receptor molecule. In hearing, on the other hand, the energy of a phonon is far lower, and detection occurs by a “classical” mechanism. For vertebrate photoreceptors and olfactory receptor cells, sensory transduction employs a G protein cascade that is remarkably similar in the two cases, and that is closely homologous to other G protein signaling cascades. For auditory and vestibular hair cells, transduction operates via a mechanism of direct coupling of the stimulus to ion channels, in a manner reminiscent of the direct gating of post-synaptic ion channels in various synaptic mechanisms. The three classes of sensory receptor cell share similarities in their mechanisms of adaptation, and it appears in each case that cytoplasmic calcium concentration plays a major role in adaptation.