Taste pathway is taught in medical schools for students to learn about the taste sensation and its perception. It is important for students to know about the taste modalities, the receptors involved, the pathway, applied aspects and differential diagnosis. Though taste disorders do not directly affect one’s life, it has an impact specifically on the quality of life. Taste disturbances can be present in those with: Bell's palsy, lesions of tegmentum in midbrain and/or pons, thalamic lesion, radiation treatment of head and neck, trauma or lesion to the taste pathway and some uncommon cause such as Sjogren’s syndrome [1]. As teachers, we have encountered questions from undergraduate students regarding the varied viewpoints in the taste pathway as given in neuroanatomy and neurophysiology text books. Recent studies about the taste pathway also support these contradicting viewpoints.
The taste buds present on the anterior 2/3rd of the tongue are innervated by the facial nerve, posterior 1/3rd by the glossopharyngeal and epiglottis by vagus. These afferent fibers relay in the nucleus of tractus solitarius (NTS). Fibers from the NTS synapse in the thalamus, which pass to the somatosensory cortex [2]. The various viewpoints put forth by fMRI studies, clinical examinations of the cranial nerves and lesions of the taste pathway shows that, the variation lies between the NTS and thalamus, which are:(a)The second order neurons from NTS synapse at thalamus and the fibers project to the ipsilateral cerebral cortex; (b) The second order neurons arising from NTS, cross to opposite side and synapse at the thalamus, which projects to the contralateral cerebral cortex; (c)‘Few’ fibers from NTS decussate and terminate at the contralateral somatosensory cortex, whereas majority of the fibres continuing on ipsilateral side, project to the ipsilateral cerebral cortex (i.e., a bilateral representation) [2–5].
In view of the various viewpoints of the taste pathway mentioned above (a, b & c), we wish to emphasize that the students need to be taught about the bilateral representation of the taste pathway. This would help the students to obtain an integrated approach of the information about the pathway given in anatomy and physiology textbooks. However, the students should also be sensitized about current concepts and research where there is a lack of evidence in regard to the taste pathway.
We wish to point out that further clinical studies are required to reaffirm this bilateral representation.
Notes
Financial or Other Competing Interests
None.
References
[1] Bromley SM. Smell and taste disorders: a primary care approach. American Family Physician. 2000;61(2):427–36. [PubMed] [Google Scholar]
[2] Kandel ER, Jessell TM, Siegelbaum SA, Hudspeth AJ, editors. Principles of neural science. 5th ed. New York: McGraw-Hill; 2013. [Google Scholar]
[3] Standring S. Gray's Anatomy. The Anatomical Basis of Clinical Practice. 40th ed. UK: Churchill Livingstone/Elsevier; 2008. [Google Scholar]
[4] Small DM. Taste and smell: An update. Basel: Karger Medical and Scientific Publishers; 2006. Central Gustatory Processing in Humans. In: Hummel T, Welge-Lüssen A, editors; pp. 191–220. (Advances in oto-rhino-laryngology; vol 63) [PubMed] [Google Scholar]
[5] Bahuleyan B. A.K.U. Gustatory pathway: A revelation based on clinical studies. Int J Cur Res Rev. 2013;5(14):24–29. [Google Scholar]
FAQs
Taste pathway is taught in medical schools for students to learn about the taste sensation and its perception. It is important for students to know about the taste modalities, the receptors involved, the pathway, applied aspects and differential diagnosis.
What is the gustatory pathway summary? ›
The gustatory pathway involves taste messages traveling to the gustatory nucleus found in the medulla. Then, the information goes to the thalamus, reaching the limbic system (processing feelings brought about by the taste sensation) and the gustatory cortex (central area of taste information).
What brain structures are part of the taste pathway? ›
The brain has a dedicated area chiefly responsible for perceiving and distinguishing different tastes called the gustatory cortex. Its location in the anterior insula in the temporal lobe and frontal opercular region is the terminal connection serving taste perception.
How do we taste step by step? ›
When taste receptor cells are stimulated, they send signals through three cranial nerves to taste regions in the brainstem — the facial, glossopharyngeal, and vagus nerves. These impulses get routed through the thalamus, which relays sensory information to other brain regions.
What controls the sense of taste? ›
“Taste, the way you and I think of it, is ultimately in the brain,” Zuker says. “Dedicated taste receptors in the tongue detect sweet or bitter and so on, but it's the brain that affords meaning to these chemicals.”
What is the process of the sensation of taste? ›
The academic term for “taste sensation” is “gustation,” which is defined as the sensation caused by activation of taste cells in oral cavity and tongue. The tastants isolated from foods and beverages bind to the taste receptor and activate the taste cells.
What is the physiology of taste perception? ›
The chemical substance activates the nerve cell by changing specific proteins in the wall of the sensory cell. This change causes the sensory cell to release chemical messengers, which in turn activate further nerve cells. These nerve cells then pass the “taste” information on to the brain.
What is the purpose of the gustatory system? ›
The gustatory system contributes to the flavor of foods and beverages and communicates information about nutrients and poisons. This system has evolved to detect and ultimately respond to hydrophilic molecules dissolved in saliva.
Why is the gustatory sense important? ›
Gustation, better known as taste, is an important special sensation that affects diet and human pleasure. Loss of taste or altered taste can occur in many disorders of the peripheral or central nervous system, and gustatory testing allows us to better diagnose and manage these conditions.
How does taste work in psychology? ›
Taste molecules bind to receptors on this extension and cause chemical changes within the sensory cell that result in neural impulses being transmitted to the brain via different nerves, depending on where the receptor is located.
The taste system encodes information about the quantity as well as the identity of stimuli. In general, the higher the stimulus concentration, the greater the perceived intensity of taste. Threshold concentrations for most ingested tastants are quite high, however.
What is taste explained? ›
The word taste, or gustation, to give its full name, refers to what is detected by the taste cells, located on the front and back of the tongue and on the sides, back and roof of the mouth. These receptor cells, or taste buds, bind with molecules from the food or drink being consumed and send signals to the brain.
What is the taste pathway? ›
Three nerves carry taste signals to the brain stem: the chorda tympani nerve (from the front of the tongue), the glossopharyngeal nerve (from the back of the tongue) and the vagus nerve (from the throat area and palate).
What triggers taste? ›
Taste is the perception stimulated when a substance in the mouth reacts chemically with taste receptor cells located on taste buds in the oral cavity, mostly on the tongue.
What is the science behind taste buds? ›
Each human taste bud has anywhere from 10 to 50 sensory cells, which are called taste hairs and are connected to nerve fibers. As a person chews, proteins bind taste chemicals to the taste hairs for taste processing. An average adult has 2,000 to 4,000 total taste buds, and taste hairs renew themselves once a week.
What is the signaling pathway of taste cells? ›
All these taste GPCRs use a common transduction pathway that includes a Gβγ-activated phospholipase C (PLCβ2) and transient receptor potential cation channel subfamily M member 5 (TRPM5). The epithelial Na+ channel (ENaC) has three subunits and is thought to transduce salty taste in rodents.
What afferent pathway is taste? ›
Information about each taste quality is then transmitted by separate afferent pathways to the gustatory cortex via the medulla and the thalamus [25]. Thus, in the labeled-line model, the function of any one neuron in an afferent pathway is to signal its particular encoded taste quality.
What is the route that the sensation of taste follows? ›
Taste neurons project from taste cells in the tongue, esophagus, and palate to the medulla, in the brainstem. From the medulla, taste signals travel to the thalamus and then to the primary gustatory cortex. Information from different regions of the tongue is segregated in the medulla, thalamus, and cortex.
How does the sense of taste get processed? ›
The chemical substance activates the nerve cell by changing specific proteins in the wall of the sensory cell. This change causes the sensory cell to release chemical messengers, which in turn activate further nerve cells. These nerve cells then pass the “taste” information on to the brain.
