Neurobiology of the gustatory sense
Taste is the perception produced or when a substance in the mouth is detected by chemoreceptors on the tongue and the inside of the mouth. Taste, along with smell (olfaction) and trigeminal nerve (part of the somatosensory system) stimulation, which detects texture, pain, and temperature, determines flavour.
The tongue and mouth
The human tongue and inside of the mouth is covered with thousands of small bumps called papillae, which are visible to the naked eye. Within each papilla are hundreds of taste buds, apart from some called filiform papillae that do not contain taste buds. There are between 2000 and 5000 taste buds that are located on the back and front of the tongue. Others are located on the roof, sides and back of the mouth, and in the throat. Each taste bud contains 50 to 100 taste receptor cells.
These receptors in the mouth sense the five taste submodalities when digestive enzymes in saliva begin to dissolve food into base chemicals, and are washed over the taste buds. The five submodalities of taste are: sweet, sour, salt, bitter and savoury (sometimes called umami).
The gustatory sense in the brain
The primary gustatory cortex is the brain structure responsible for the perception of taste. It consists of two substructures: the anterior insula on the insular lobe and the frontal operculum on the inferior frontal gyrus of the frontal lobe.
Research shows that the perception of taste plays an essential role in food identification (for safety among other things), selection and for food control. In research with monkeys, cortical response to tase stimulus was reduced when the monkey near satiety.
Function of the gustatory sense
Taste and texture contribute to the perception of flavour, providing information that allows humans to distinguish between safe and harmful food, and to select foods that they need by gauging their nutritional makeup. It is also thought that taste and particularly texture can influence satiety.
As the gustatory system senses both harmful and beneficial things, all basic taste modalities are classified as either aversive or appetitive, depending upon the effect the things they sense have on our bodies. Sweetness helps to identify energy-rich foods, while bitterness serves as a warning sign of poisons.
Regulation of the gustatory sense
The gustatory and olfactory systems are the most highly subjective in terms of perception. Humans perceive tastes and smells in highly individual ways, and both are closely linked to memory and pleasure, leading to the regulation of taste and texture being highly emotive, and often linked with mental health, as well as neurodiversity.
Gustatory sense sensitivity
People who are highly sensitive to tastes and textures of food can be left with a severely restrictive diet, and therefore poor energy, and nutrition.
Supertasters
Research suggests that some people are genetically more sensitive to bitter tastes, through general increased sensitivity, and potentially having more taste receptors. These people are commonly avoidant of certain types of vegetables, and seek sweet foods even more than usual.
Oral hypersensitive characteristics
- Gags easily, sometimes at the mere thought of certain foods
- Prefer not to mix food textures
- Refuse many types of food
- Has aversion to certain textures, tastes or temperatures of food
- Appear to be fussy eaters (diet often referred to as beige)
- Struggles to brush teeth due to aversion of items in their mouth
- Refuse to lick items such as stamps or envelopes
- Need to control mealtime experience, such as when, where and what they eat with.
Oral hyposensitive characteristics
- Constantly put objects, fingers, or food in their mouth
- Chews items such as pens, clothing, fingers or hair
- Overstuffs their mouths at mealtimes
- Prefers more extreme tasting foods
- Adds high levels of condiments or seasoning to food
- Licks, tastes or smells things that others wouldn’t
- Enjoys trips to the dentist.
