Introduction
In the past few decades, the field of neuroscience and research has made remarkable progress in defining and understanding the gustatory perceptions in humans. This journey has led to a profound understanding of how taste perceptions are experienced through the sensory intricacies of the taste buds located on the tongue. Furthermore, scientific inquiry has extended its reach to encompass the tactile and temperature-induced changes that individuals encounter within the oral mucosa and the oral cavity. This article discusses taste perception in humans, exploring whether the commonly held belief about the impact of aging on taste perceptions holds.
How Does Taste Perceptivity Work in Human Beings?
In a healthy person or group of people, taste perceptivity is guided by the central taste pathway. Many studies from around the world show that the ability to taste does not decline as people get old. Aging does not have much impact on the tiny taste buds on the tongue, according to the science of how the nerves work. Neurophysiological investigations have firmly established that aging exerts minimal influence on the intricate apparatus of taste buds. As an individual ages, the sense of taste does not change much. The biggest changes in taste buds happen when growing up, as kids and teenagers. The taste buds start forming when the fetus is just seven or eight weeks old inside the womb. They get more developed as they approach birth, but their development remains incomplete at the time of birth.
After childbirth, the taste sense gets stronger during infancy because more taste buds develop. Throughout their entire lives, the way of tasting food stays pretty consistent. This means the ability to enjoy food does not go down much as we get older.
What Are the Factors That Cause Loss of Taste Sensation?
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Loss of taste can result from various causes.
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Damage or insufficient production of saliva from salivary glands can affect the taste.
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COVID-19 infection can lead to temporary taste loss, typically recovering after other symptoms.
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Certain medications like antibiotics (Ampicillin, Azithromycin), cholesterol-lowering agents (statins), and blood pressure drugs (angiotensin-converting enzyme (ACE) inhibitors) can alter taste.
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Some medications cause dry mouth, affecting taste and swallowing.
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Seeking medical advice is crucial if the medication affects taste; alternatives might exist.
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Dental problems, like gum disease or denture issues, can distort taste.
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Maintaining good oral hygiene through brushing, flossing, and mouthwash can help.
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Alcohol consumption can change how food tastes; reducing or quitting may help.
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Smoking can reduce the sense of taste; quitting smoking may lead to improvement.
What Is the Role of the Central Taste Pathway in the Cranial Nerves?
The ability to taste is connected to three main cranial nerves. These nerves are like communication lines between our brains and the taste buds. They are named cranial nerve VII (facial nerve), cranial nerve IX (glossopharyngeal nerve), and cranial nerve X (vagus nerve). All of them lead to a special area in the brain called the nucleus tractus solitarius.
Each of these cranial nerves has a group of cells called ganglia that corresponds to it. These are the geniculate, petrosal, and nodose ganglia. Among them, the glossopharyngeal nerve is important because it sends more messages to the taste buds. The facial nerve does not send as many taste-related messages, and the vagus nerve takes care of the tongue and mouth, sending many signals about the taste of what we eat.
The special area in the brain, the nucleus tractus solitarius, is where the messages from these three nerves meet. It is like a central station for taste signals. But this area does not just help with taste but is also involved in important things like helping us swallow, breathe, cardiovascular reflexes, and gastric motility.
How Does the Process of Taste Perception Occur in Different Parts of the Human Brain?
The pathway of taste perception in different parts of the brain occurs in the following sequence :
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Nucleus Tractus Solitarius: Scientists and doctors have studied the gustatory neurons in a part of the brain called the nucleus tractus solitarius. They use recordings to understand how these neurons respond when the tongue tastes something. These neurons show certain patterns when stimulated, and other neurons react a lot when they sense taste. These second-order neurons are more responsive than the first ones in the nucleus tractus solitarius.
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Pontine Relay Neurons: After leaving the nucleus tractus solitarius, taste signals go to the pontine taste relay in non-primates. In primates, like humans, the taste signals go even further to a part of the brain called the thalamus. This means different species' processes taste a bit differently. In humans, the taste signals then move to the pons in the brain, where special neurons called pontine neurons are organized. These neurons respond even more strongly than the second-order neurons in the nucleus tractus solitarius. These studies also show that certain taste buds react to things like salt, acid, and sugar.
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Thalamus: Another part of the brain called the ventrobasal complex in the thalamus also plays a role in tasting. Neurons here respond to specific tastes, but they can also react to touch and temperature changes in the mouth.
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Cortex: The brain cortex also significantly contributes to the perception of gustation upon stimulation.
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Miscellaneous Termination or Projections of Gustatory Neurons: In the brain, the accessory projections of these gustatory neurons penetrate the lateral part of the hypothalamus, the amygdala central nucleus, as well as the nucleus bed of the stria terminalis of the brain. It is these projections into these different miscellaneous parts of the human brain that are responsible for motivation, emotions, as well as any behavioral reinforcement regarding the intake and perception of food.
Conclusion
The peripheral taste system remains well-functioning and unchanged throughout an individual's life, and it does not have much to do with the process of getting older. The main pathway for taste signals, including the gustatory neurons in the nucleus tractus solitarius and the connections to the brain's cortex, stay the same as getting older. Interestingly, there is not much evidence to show that the way of taste sensation changes a lot as one gets older. The ability to taste things through the mouth is stronger than in most other species, and age does not affect how one experiences taste all that much.
