The relationship between taste and smell in the human body

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

In this article we will learn about this link between both senses. Has a dish ever smelled so good that you thought, "If it tastes like it smells it will be delicious!" Here we will discover if there really is such a relationship between these two senses, as had always been thought.

• Related article: "The 5 types of flavors, and where are their receptors on the tongue"

How do these senses work?

Until a smell is perceived, 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 certain signal or external stimulus into another specific signal or response. Then a second messenger system is activated that causes the depolarization of the sensory neuron and the action potential.

In addition, smell is the only sensory system whose information does not take over in the thalamus before reaching the primary cortex. What's more, cortical processing is ipsilateral; This means that the information does not change sides in the brain, that is, the information that enters through the left nostril it is processed in the left hemisphere, and the same with the part right.

Olfactory cells are bipolar; the axons sensitive synapts with 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, receptors for acid and salty are ionotropic, and receptors for sweet taste are metabotropic; both types of receptors act for bitter.

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

Unlike what happened with olfactory information, taste information does take over in the brain; the first relay is in the Nucleus of the Solitary Tract (bulb). This information then goes to the protuberant 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 get to 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 various studies on the relationship between taste and smell. One of its researchers, Eduardo Weruaga, affirms that many times people confuse concepts such as taste, taste and smell, but that they are very different things.

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

In line with these claims, it is also known that many people who begin to lose the taste of food and that believe they are losing taste, what they are actually losing is smell, the main component of that sensation.

Results to the 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 to the Spanish Olfactory Network, carried out five years ago a series of workshops where they presented these two senses, and experimented with substances that the they stimulated.

This group claims that not all people smell and taste the same, and 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 "super-tasters" and others who are precisely 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 both are "chemical senses", since identify chemicals in the environment.

Eduardo Weruaga, the researcher, points out that “the smell detects volatile chemical substances that are dissolved in the air, which cannot be done by the taste buds of the mouth, and the taste detects substances dissolved in water ”. These are two environmental media that do not mix in nature, and therefore cause us to detect different substances in 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 the brain level they are not Really). To illustrate the latter, let's think for example when we say "this dish tastes like how it smells", or "if it tastes like it smells, it will be great.

In short, according to these studies, the neural pathways of taste and smell have nothing to do with each other, although the perception of these occurs jointly once it reaches the brain.

Pathologies with loss of smell

Human beings give more importance to vision or hearing, compared to taste and smell (unlike what happens with other animals). This means that taste and smell are so little studied, although there are some 300 pathologies that include loss of smell among their symptoms. The total loss of smell is called anosmia, and the partial loss, hyposmia.

For example, Parkinson's or Alzheimer's have certain neurological losses that affect smell. However, experts say that smell is often lost due to causes other than neurology, such as For example, plugging of the nasal passages by polyps (parts of extra tissue that grow inside the Body).

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

The emotional memory associated with smells

On the other hand, smell, unlike the rest of the senses (including taste), is a very emotional type of perception or sense, since is connected with brain areas responsible for managing emotions.

Olfactory memory is said to be the most powerful, and olfactory memories (certain smells or scenes associated with a specific smell), if they are also emotionally charged, they are remembered a lot 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. Culture Spain.
• Carlson, N.R. (2005). Physiology of behavior. Madrid: Pearson Education.
• Netter, F. (1989). Nervous system. Anatomy and physiology. Barcelona: Salvat.