Taste and smell are two senses that, although important, have always been overshadowed by others such as sight and hearing. This implies 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 both directions. Have you ever smelled a dish so good that you thought, “If it tastes like it, it will be delicious! Here we will find out if there really is as much of a link between these two senses, as had always been thought.
How do these senses work?
Until an odor is perceived, a series of steps are taken: first the odorants enter the nasal cavity and are detected by the metabotropic receptors . Then transduction occurs, that is, the process by which a cell converts a certain signal or external stimulus into another specific signal or response. A system of second messengers is then activated, causing depolarization of the sensory neuron and action potential.
Furthermore, the sense of smell is the only sensory system whose information does not take over in the thalamus before it reaches the primary crust. Furthermore, cortical processing is ipsilateral ; this 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 goes for the right side.
The olfactory cells are bipolar ; the sensory 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
As for the ability to perceive flavors, there are 4 submodalities of taste (types of taste): salty, sweet, sour and bitter (although a new one has recently been discovered, umami). At the brain level, the receptors for acid and salt are ionotropic, and the receptors for sweet taste are metabotropic; for bitter, both types of receptors act.
Here the sequence that takes place at the brain level to end up appreciating the flavors is the following: the taste information is transported by the cranial nerves Facial (VII), Glossopharyngeal (IX) and Vagus (X) .
Unlike olfactory information, gustatory information does take over in the brain; the first relay is in the Lone Tract Nucleus (bulb). After that, this information goes to the pro-tuberancial gustatory area, and from there to the Posteromedial Ventral Nucleus of the Thalamus (mostly ipsilateral pathways). Finally the neurons project to the Primary Taste 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 Castilla y León Institute of Neurosciences (INCYL) of the University of Salamanca are developing various studies on the relationship between taste and smell. One of their researchers, Eduardo Weruaga, says that many times people confuse concepts such as taste, smell and flavor, but they are very different things.
When we taste something, in fact the olfactory component is much more important than the gustatory component , although we usually think otherwise. That’s why when we have a cold we stop noticing the flavours (“everything tastes like nothing”), due to our nasal congestion (our sense of smell is “annulled”).
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 the taste, what they are actually losing is the smell, the main component of that sensation.
Results to studies
To explain the relationship between taste and smell, the group of scientists from the Instituto de Neurociencias de Castilla y León (INCYL) of the University of Salamanca, together with the Red Olfativa Española, held a series of workshops five years ago where they presented these two senses, and experimented with substances that stimulate them.
This group states that not all people smell and taste the same , and that some have more potential than others. They also maintain that in some cases there is a genetic component that would explain why there are some people who are “supertaskers” and others who are precisely the opposite. As for smell, this is not known any more.
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 chemical substances 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 environmental media that do not mix in nature, and therefore make us detect different substances by different routes .
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 a cerebral level they are not really linked). To illustrate this last point, let’s think for example about when we say “this dish tastes like 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
Humans attach greater importance to vision or hearing, compared to taste and smell (unlike other animals). This means that taste and smell are so little studied, even though there are some 300 pathologies that include among their symptoms the loss of smell. 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 the sense of smell. However, experts say that smell is often lost due to non-neurological causes, such as blocked nostrils from polyps (extra tissue growing inside the body).
In the case of colds or flu, we can also lose our sense of smell; even if less frequently, permanently.
The emotional memory associated with odors
On the other hand, smell, unlike the rest of the senses (including taste), is a very emotional type of perception or sense, since it is connected to brain areas in charge of managing emotions .
It is said that the olfactory memory is the most powerful, and that olfactory memories (certain smells or scenes associated with a particular smell), if they are also emotionally charged, are remembered much more.
- 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). Behavioral physiology. Madrid: Pearson Educación.
- Netter, F. (1989). Nervous system. Anatomy and physiology. Barcelona: Salvat.