Retronasal Olfaction
Alan R. Hirsch in Nutrition and Sensation, 2023
Olfaction is the process by which chemical stimulants are processed into the sensation of smell. In this, aerosolized chemical stimulants traverse the nose, move into the olfactory cleft, and eventually contact the olfactory sensory neurons. With a sufficient stimulus, the sensory signal of smell is triggered. This is considered a chemosensory process, as the stimulus is a chemical that binds to a receptor. Most of the other human senses use different stimuli. Vision uses light; hearing uses sound waves; touch uses pressure. All of those sources are not from a chemical stimulus. Using chemicals to stimulate a response is known as chemosensation. Olfaction shares chemosensation with the sense of taste. Smell and taste are strongly linked in this regard. In fact, 90% of taste, or flavor, is actually smell (Hirsch 1992a). Despite the close association, there are significant differences between smell and taste.
Smell Perception/Anosmia/Parosmia
Charles Theisler in Adjuvant Medical Care, 2023
Anosmia is the complete loss of smell. Nasal congestion is a common cause of temporary anosmia. Loss of smell from nasal polyps, sinusitis, upper respiratory tract infection, or fractures is due to intranasal swelling or other obstruction that prevents odors from gaining access to the olfactory area. Neurologic causes include head trauma and viral infections, as well as aging or Alzheimer's. A number of other conditions can cause anosmia as well. Parosmia, or dysosmia, describes a distortion or perversion of the sense of smell. What typically happens is that natural and pleasant odors are perceived as offensive and disgusting. Additional causes can include Alzheimer's, Huntington's, or Parkinson's, and olfactory damage from head injury, bacterial or viral infection, toxic chemicals, radiation, or chemotherapy, etc. Neurologists have used sodium valproate, gabapentin, and pregabalin to treat parosmia for decades with good results.1
The Special Sense Organs and Their Disorders
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss in Understanding Medical Terms, 2020
Parosmia and parosphresia, from the Greek words osme and osphresis (meaning smell or smelling), refer to any disorder of the sense of smell, especially the subjective perception of odors that do not exist. Loss of the sense of smell is termed anosmia (also, olfactory anesthesia or smell blindness). The types of anosmia, according to their cause, are essential or true, due to lesion of the olfactory nerve; mechanical or respiratory, due to obstruction of the nasal fossae; reflex, due to disease in some other location; and functional, without any apparent cause. Nasal congestion ('"stuffy nose") caused by allergic rhinitis, bacterial or viral inflammation, or anatomical defects will also interfere with the sense of smell.
Individual Differences in Chemosensory Perception Amongst Cancer Patients Undergoing Chemotherapy: A Narrative Review
Published in Nutrition and Cancer, 2022
Alba Ruiz-Ceamanos, Charles Spence, Jordi Navarra
Future research on genetic individual differences related to taste and smell perception (93, 142) would probably help in the understanding of the different alterations in cancer patients taste, smell and flavor perception. Similarly, greater recognition of the role played by the composition of saliva and its capacity to modulate flavor perception may also prove important. Besides, and perhaps more importantly, future research that focuses on naturalistic flavor perception instead of merely the evaluation taste and smell thresholds separately may be able to solve the apparent contradictions seen earlier (143). One cannot ignore the need to clarify the numerous confusions between the terms smell, flavor, and taste (and even between basis taste descriptors such as bitter or sour) either, especially to participants in taste, smell and flavor perception studies.
Patients’ multifaceted views of dental fear in a diagnostic interview
Published in Acta Odontologica Scandinavica, 2021
Pirjo Kurki, Maija Korhonen, Kirsi Honkalampi, Anna Liisa Suominen
Nearly all participants were able to name/identify the most fearful aspect and we labelled the category, the fear of an extreme reaction, including fear of an allergenic reaction, fear of choking, fear of drowning, shortness of breath or fear of a panic attack: ˈSometimes I’ve had a feeling of drowning just thinking about having to go againˈ. Furthermore, most participants told about the fear of failure in a technical procedure, especially in local anaesthesia regarding the right location for the injection or pain during injection. Many mentioned the fear related to the dentist’s behaviour. All participants recognised objects of fear, which were described in three subcategories: fear of pain, fear of injections and distrust in their own ability to cope with the fear: ˈDuring a root canal treatment, I’m afraid of whether I can keep my mouth open ‒ what if it snaps shut while the spikes are in there? ˈ. Additionally, most participants felt uncertainty and they were worried about the dentist’s unclear language and about sounds/smells at the dentist’s office. Recollection of previous treatment situations during dental treatment was also typical, and the participants remembered fearful situations from the past: ˈ…that horrible memory of fleeing from there is all I can remember, and the stench used to be nauseating back in the day. These days, the smell isn’t that bad, even if they have all those chemicals thereˈ.
The incidence of anosmia after traumatic brain injury: the SHEFBIT cohort
Published in Brain Injury, 2018
Rajiv Singh, Thomas Humphries, Suzanne Mason, Fiona Lecky, Jeremy Dawson, Saurabh Sinha
Future work needs to establish the nature of the relationship between anosmia and depression with particular regards to the anatomical link and frontal lobe damage. Documentation of CT abnormality needs to describe the exact location of the lesions rather than the extent of lesions. In addition the relationship with other possible frontal lobe impairments such as executive function or verbal fluency may be conducted. It is important to distinguish between subtle changes in smell which are often unnoticed by the individual and more significant, clinically relevant anosmia which has been investigated in this study. Within constraints of busy clinical practice, assessment has to be reliable but practical and much of the established literature is impractical for busy clinicians.
Related Knowledge Centers
- Glomerulus
- Memory
- Olfactory Bulb
- Olfactory Receptor
- Olfactory System
- Pheromone
- Taste
- Nasal Cavity
- Special Senses
- Odor