Tuberculum Olfactorium: Structure, Function & Diseases

The olfactory tubercle is a small bump in the skull that contains the human brain. It is a part of the olfactory pathway. It is through it that olfactory perception enters the human consciousness.

What is the olfactory tubercle?

The olfactory tubercle is also known as the olfactory bulb. Information or stimuli picked up from the air are transported from the olfactory mucosa of the nose to the further centers of the brain for evaluation. The olfactory bulb is significantly involved in this process. It has a strong influence on whether a person continues to turn toward or away from a perceived stimulus from the air. However, this does not so much imply odors of danger. Rather, it is about emotionally triggered odors. This can influence various areas of life. The choice of a partner, for example. Smells associated with pleasure, such as food, are also evaluated by the olfactory tubercle. If the odor is perceived as pleasant, a behavior such as affection is triggered. If the odor is perceived as negative, the tuberculum olfactorium causes motivational behavior that results in turning away. From an evolutionary point of view, the olfactory tubercle belongs to the oldest part of the human cerebrum. It is assigned to the paleocortex and represents a small area in the cerebrum.

Anatomy and structure

The paleocortex and its structures make up the human olfactory brain. It consists of the bulbus as well as tractus olfactorius, the tuberculum olfactorium , the septum with the stria diagonalis, the prepiriform cortex and parts of the amygdala, the corpus amydgaloideum. The olfactory nucleus is located in the olfactory tract. In it, impulses from the bulbus olfactorius are interconnected and transmitted to the opposite side of the olfactory cortex. Projection targets are located in the stria olfactoria lateralis. Their task is to transport the perception via smell into the consciousness of the person. They include the prepiriform cortex, the enorhinal cortex, and the corpus amygdaloideum. The stria olfactoria medialis contains the tuberculum olfactorium as well as the septal region. The tuberculum olfactorium is closely associated with the nucleus accumbens. In the region around the olfactory tubercle, there are numerous vascular entrances on its surface. Therefore, this area is also called substantia perforata anterior. Opposite to this is the substantia perforata posterior. It is located between the two crura cerebri.

Function and tasks

The function of the olfactory tubercle is the process of becoming aware of the recorded odor. It processes the olfactory stimuli that are received and transmitted through the nose. The olfactory tubercle has no influence on perception itself. However, it is involved in modulating the behavior triggered by an odor. In most cases, stimuli are received multisensory. This means that information is received via the various sensory organs that can be causally assigned to a source. Food, for example, has a certain appearance, smells in a certain way, and has a certain taste. All of these together are processed in the brain and result in other components of a served meal being picked up or leaned upon. The olfactory tubercle is associated with the emotional and motivational areas of the olfactory system. The information received through the olfactory mucosa flows through the tractus olfactorius, the stria olfactoria medialis and the tuberculum olfactorium and on to the septum. This is located in the medial hemisphere, that is, in the middle area of the brain. In the tuberculum olfactorium there are dopaminergic neurons. Dopamine has an important influence in the human organism on functions such as reward. This means that the tuberculum olfactorium has the task of valuing odors perceived as pleasant more highly. At the same time, it is involved in reinforcing or implementing the motivation of turning away in the presence of a negative odor.

Diseases

Impairments of the olfactory tubercle lead to an influence on the reward center in the human organism. This means that a change in behavior can be expected when there is a dysfunction of the tuberculum olfactorium. Odors that were previously considered pleasant are perceived as neutral when lesions are present. This has implications for social behavior and in processes associated with a sense of pleasure.Odors such as perfume, the intrinsic odor of another person, the environment or food are perceived as no longer pleasant or less unpleasant. In particular, the intake of food is tied to a multisensory processing of the different stimuli. The smell of coffee already triggers certain associations. They may be associated with alertness or heightened attention. The smell of a main meal already triggers salivation in the mouth. The same happens with sweet foods. As soon as the tuberculum olfactorium is no longer fully functional, a corresponding restriction occurs. In addition, a person’s smell is important in the choice of a partner. A partner with a genetically identical material is not chosen evolutionarily to produce offspring. Rather, the choice falls on a partner with whom the offspring will produce the highest chances of survival as well as the most stable immune system. As soon as the olfactory sensation is limited, the assessment changes. A partner’s odor that was previously considered pleasant can no longer be adequately perceived. Automatically, in certain nuances, the social behavior towards this person changes. The proverbial “I can’t smell this person” is based on true evolutionary causes and finds one of its origins in the tuberculum olfactorium.