How Does Taste Work in the Brain?

The part of the brain responsible for taste (gustation) is known as the gustatory cortex or primary gustatory cortex. It is involved in the perception and differentiation between different types of taste [1].

However, there are several steps before taste information reaches the gustatory cortex for processing:

• When a food is consumed, its breakdown in the mouth liberates chemical substances that interact with the tongue surface that contains raised bumps known as papillae.

The papillae contain taste buds that are specialized in detecting the types of taste through receptors known as gustatory receptors.

The gustatory receptors release neurotransmitters that activate sensory neurons (neurons involved in sensation) in proximity.

• The activation of the sensory neurons transmits (neurotransmission) the taste information (gustatory information) to facial and glossopharyngeal cranial nerves.

• Upon reception of the taste information, the nerves transmit it to a part of the brain known as the gustatory nucleus found in the medulla oblongata located in the lower part of the brainstem.

The medulla oblongata is responsible for several functions in the autonomous nervous system (involuntary nervous system), including swallowing, vomiting, sneezing, and coughing, ventilation, heartbeat, blood pressure.

• The gustatory nucleus in the medulla oblongata will then transmit the taste information to the thalamus which relays the information to the gustatory cortex for processing.

The thalamus is a part of the forebrain involved in the regulation of alertness, sleep, and consciousness.

It is also important to add that gustation (taste) is strongly linked to olfaction (smell) as the flavor of any type of food requires a combination of the two senses.

1. What Are the 5 Types of Taste?

The chemical substances that are generated during the breakdown can be classified as sweet, salty, sour, bitter, and umami [2]. However, some foods may have a mixture of more than 2 types of taste.

Sweet

A sweet taste is due to the presence of sugars such as glucose, fructose, or artificial sweeteners including aspartame, sucralose, or saccharine.

Salty

A salty taste is due to the presence of sodium chloride and other salts.

Sour

A sour taste is due to the presence of acids such as citric acid (orange juice)

Bitter

A bitter taste is the opposite taste to the acidic taste and is due to the presence of alkaloids that are mostly found in plants such as tea, coffee, aspirin, and tannins.

Umami

Umami taste is due to the presence of amino acids that form proteins found in meaty products.

Fatty taste is another type that has been proposed as a specific receptor for the omega 3 fatty acid, linoleic acid, was identified. Linoleic acid is mainly found in plant oils.

In addition, hot or spicy are not considered as tastes as they are pain signals associated with touch and temperature.

Taste qualities are also associated with the ability to distinguish between pleasant and unpleasant tastes but also between poison from food.

For example, most people tend to prefer sweet and umami tastes, while sour and bitter tastes are less preferred.

2. How Many Taste Buds Do Humans Have?

Humans have between 2000 to 4000 buds in total and are found in the papillae of the tongue but also in the back of the throat, nasal cavity, epiglottis, and the upper part of the esophagus. They are renewed every week [1].

Each taste bud contains between 10-40 gustatory receptors (sensory cells).

Papillae are divided into fungiform papillae (200-400 papillae), circumvallate papillae (7-12 papillae), and foliate papillae (about 20 papillae).

3. What Is a Flavor?

A flavor is a perception of food that combines taste and smell. It is mediated by the trigeminal nerve responsible for facial sensations, biting, and chewing.

4. What Are the Main Components of Flavor?

The main components of flavor include:

• Tastes (Sweet, bitter, acid, umami, and salty)
• Aroma (Pleasant smell from consumed food)
• Trigeminal Sensations (Facial sensations mediated by the trigeminal nerve)

6. What Part of the Brain Controls the Tongue?

The muscles monitoring the movement of the tongue are controlled by the medulla oblongata through the hypoglossal nerve.

7. What Causes a Person to Lose Taste?

The loss of taste is known as ageusia that can be due to several causes [3]:

• Head injury
• Middle ears or upper respiratory infections
• Dental problems or inadequate oral hygiene
• Environmental exposure to chemicals
• Medications
• Head and neck cancer radiotherapy
• Some surgical procedures involving the nose, ear, or the throat.

Disorders of taste can manifest in the following forms:

• Ageusia is disorder characterized by the complete absence of taste.
• Hypogeusia is adiminished taste.
• Hypergeusia is characterized by an enhanced perception of taste.
• Dysgeusia or parageusia is a distortion of tastemainly associated with an unpleasant perception of taste.

8- What are the symptoms of Taste Disorders?

• Changes in the taste of food and beverages that are usually consumed
• Changes in the intensity of taste of consumed food and beverages
• Absence or loss of taste
• Loss of weight associated with a loss of appetite

8- How are Taste Disorders Diagnosed

The otolaryngologist can assess the taste disorder by measuring the capacity of the affected individual to taste different types of tastes [3].

As taste disorders can be associated with middle ear and upper respiratory infections, the otolaryngologist will also examine potential problems with the ears and the throat.

For potential causes associated with poor dental hygiene, a dental examination is also performed.

8. How Can I Improve My Sense of Taste?

Treatment and improvement of the sense of taste depend on the cause of the taste disorder.

 however, some of these disorders can be prevented by ensuring good oral hygiene, consuming a variety of foods with different flavors, and staying patient when affected by cold.

Conclusion

Taste is very important for our everyday life. Not being able to taste a good dish of food or a beverage can be extremely stressful, and in some cases, can lead to a loss of appetite, weight loss, and depression. Unfortunately, it is only when we are having issues with our taste that we remember how important it is in our everyday life.