The relationship between taste and smell in the human body

The ability to taste substances and detect odors are related abilities.

Taste and smell are two senses that, although important, have always been overshadowed by others such as sight or hearing. This means that they have been little studied. However, we do know that there is a relationship between taste and smell..

In this article we will learn about this link between the two senses. Have you ever had a dish smell so good that you thought, "If it tastes like it smells, it must be delicious! Here we will discover if there really is as much of a link between these two senses as we had always thought.

How do these senses work?

Until we perceive a smell, a series of steps are taken: first odorants enter the nasal cavity and are detected by metabotropic receptors.. Transduction then occurs, that is, the process by which a cell converts a specific signal or external stimulus into another signal or specific response. A second messenger system is then activated, which causes depolarization of the sensory neuron and the action potential.

In addition, olfaction is the only sensory system whose information does not relay to the thalamus before reaching the primary cortex. In addition, cortical processing is ipsilateralThis means that information does not change sides in the brain, i.e., information entering through the left nostril is processed in the left hemisphere, and the same with the right side.

Olfactory cells are bipolarThe sensitive axons synapse with the dendrites of the olfactory bulb, in units called glomeruli.

The olfactory system is divided into two:

• Main system
• Accessory or vomeronasal system

Regarding the ability to perceive flavors, there are 4 submodalities of taste (types of taste): salty, sweet, sour and bitter (although a new one, umami, has recently been discovered). At the brain level, the receptors for sour and salty taste are ionotropic, and the receptors for sweet taste are metabotropic; for bitter taste both types of receptors act.

Here the sequence that occurs at the cerebral level to end up appreciating the flavors is the following: taste information is carried by the cranial nerves Facial (VII), Glossopharyngeal (IX) and Vagus (X)..

Unlike what happens with the olfactory information, the gustatory information does relay in the brain; the first relay is in the Nucleus of the Solitary Tract (bulb). Then this information goes to the protuberancial gustatory area, and from there to the Posteromedial Ventral Nucleus of the Thalamus (mostly ipsilateral pathways). Finally, the neurons project to the primary gustatory cortex..

The relationship between taste and smell

But what is the relationship between taste and smell? Let's know it in detail.

A group of scientists from the Institute of Neurosciences of Castilla y León (INCYL) of the University of Salamanca are developing several studies on the relationship between taste and smell. One of their researchers, Eduardo Weruaga, states that people often confuse concepts such as taste, flavor and smell, but that they are quite different things.

When we taste something, the olfactory component is actually much more important than the gustatory component, although we tend to think otherwise.although we tend to think otherwise. That is why when we have a cold we stop noticing flavors ("everything tastes like nothing"), due to our nasal congestion (our sense of smell is "overridden").

In line with these statements, it is also known that many people who start to lose the taste of food and think they are losing their taste, what they are actually losing is their sense of smell, the main component of that sensation.

Results to studies

To explain the relationship between taste and smell, the group of scientists from the Institute of Neurosciences of Castilla y León (INCYL) of the University of Salamanca, together with the Spanish Olfactory Network, carried out five years ago a series of workshops where they presented these two senses, and experimented with substances that stimulated them.

This group affirms that not all people smell and taste the sameand that some have greater potential than others. They also argue that in some cases there is a genetic component that would explain why there are some people who are "supertasters" and others who are just the opposite. As for smell, this is more unknown.

Differences and similarities between taste and smell

Continuing with the relationship between taste and smell, we know that the only neurological relationship between these senses is that they are both "chemical senses" in that they identify chemicals in the environment.

Eduardo Weruaga, the researcher, points out that "smell detects volatile chemicals that are dissolved in the air, which cannot be done by the taste buds in the mouth, and taste detects substances dissolved in water". These are two media in the environment that do not mix in nature, and which therefore make us detect the different substances by different ways..

On the other hand, the relationship between taste and smell is present for example in different foods, or in the fact that we perceive that "taste and smell" are linked (although at brain level they are not really linked). To illustrate the latter, let's think for example when we say "this dish tastes like it smells", or "if it tastes like it smells, it will be delicious".

In short, according to these studies, the neural pathways of taste and smell have nothing to do with each other, although their perception occurs together once they reach the brain.

Pathologies with loss of smell

Humans give more importance to vision or hearing than to taste and smell (unlike other animals). This is why taste and smell are so little studied, although there are about 300 pathologies that include loss of smell among their symptoms. Total loss of smell is called anosmia, and partial loss is called hyposmia..

For example, Parkinson's disease or Alzheimer's disease are associated with certain neurological losses that affect the sense of smell. However, experts say that smell is often lost due to non-neurological causes, such as clogging of the nasal passages by polyps (pieces of extra tissue that grow inside the body).

In colds or catarrhs we can also lose our sense of smell; even, although less frequently, permanently.

Emotional memory associated with smells

On the other hand, smell, unlike the other senses (including taste), is a very emotional type of perception or sense, as it is connected to brain areas responsible for the perception of smells. is connected with brain areas responsible for the management of emotions..

It is said that the olfactory memory is the most powerful, and that olfactory memories (certain smells or scenes associated with a specific smell), if they are also emotionally charged, are remembered much more.

Bibliographic references:

• Ibero-American Agency for the dissemination of science and technology. (2014). Taste and smell are "chemical senses", but they are not related in the brain. Cultura España.
• Carlson, N.R. (2005). Physiology of behavior. Madrid: Pearson Educación.
• Netter, F. (1989). Nervous system. Anatomy and physiology. Barcelona: Salvat.