Taste: Physiology, roles and dysfunction

The sense of taste involves multimodal sensory activation to detect and identify many flavors. Today, five primary tastes have been identified (sweet, salt, sour, bitter and umami). These are often combined to form complex tastes. The physiology of gustatory pathways is complex. The activation of gustatory receptors located in the mouth leads to an ascendant pathway through the neurons of the solitary nucleus in the brainstem and the neurons located in the thalamus. After the thalamus, the gustative signal modulates the ipsilateral primary taste cortex and then the secondary taste area. The secondary taste cortex, which combines representations of taste and smell, allows cortical processing and the convergence of the different sensory pathways. The other sensory modalities, such as somatosensory, olfactory, visual and hearing modalities, also interact with gustation at different stages of gustative integration. The sense of taste has three main roles: to detect and identify foods that can be eaten, to provide information in the decision to ingest or reject the food, and to trigger the digestion, absorption and storage of food. Taste problems are frequent and not diagnosed often enough. If physicians do not take them into account, they can worsen the underlying disease by causing malnutrition. Many drugs and diseases can cause gustatory loss. The underlying mechanisms are various and often unknown. Increasing our knowledge of taste physiology could improve our understanding of taste pathology. The main aim is to treat taste problems in order to avoid malnutrition and aggravation of the underlying disease. (C) 2013 Elsevier Masson SAS. All rights reserved.