Habenula: What It Is, Characteristics And Functions In The Brain
In this article we will learn what the habenula is and we will see what its parts are, what functions it performs, where it is located and what its implications are for human behavior.
The habenular nucleus, also called habenula or habenular commissure, turns out to be a relatively unknown brain structure for the general population and even for various health professionals; however, even though it may be very small, it fulfills very important functions. In short, it is a tiny (half the size of a pea) structure of nerve fibers The habenula is a tiny (half the size of a pea) region of the brain and is involved in afferents and efferents.
On the one hand, it receives input from the brain through the thalamic stria medullaris and output to many areas of the midbrain. Its main functions consist of interconnecting and communicating different nuclei, allowing the passage of information through the components of the thalamus. Therefore, it meets an important role for the communication of the various parts of the brain
The term habenula is in reference to the elongated shape it presents. From the beginning it was thought that the functions it fulfilled were linked to the regulation of the pineal gland, however, the most current evidence shows that the habenula plays the role of a neuroanatomical center that regulates and connects the most important brain regions for that motivational states and cognitions (decision making) are configured.
In the habenula or habenular nuclei it has two parts: the lateral habenular nucleus and the medial habenular nucleus. The habenula turns out to be quite unknown to many people; However, the main function it performs is to modulate the different brain structures.
Likewise, it is linked, considering the neurotransmitters it regulates, with gratification, pleasure, cognition and reinforcement The most relevant and important function performed by the habenula is to communicate synaptic information, which involves the release of neurological modulators (serotonin, dopamine and norepinephrine). The habenula is located in the epithalamus, specifically inside the diencephalon.
Specifically, it is located in the forebrain with structures such as the thalamus, the pineal gland and the hypothalamus (structures that stand out for their connection with the limbic system). It is important to highlight that the habenular nuclei or habenula are connected to the pineal gland and facilitate the connection between the reticular formation and the limbic system.
The processes carried out by the habenula
The habenula has been linked to the following processes: sleep and wakefulness, reward responses due to its links with the limbic system, sexual behavior, behavioral responses to pain, decision making (it causes us to take risks in events in which we express fear) and the evocation of emotions based on smells since it has olfactory afferents.
Effects of alterations in the habenula
The various dysfunctions, conditions and alterations of the habenula reveal the following symptoms: Excessive focus on negative aspects, tendency to show little interest and pleasure in things that are ordinarily pleasurable for any person, hyperactivation in those individuals who present a picture of major depression, signs or symptoms similar to those presented by people with ADHD (Attention deficit disorder and hyperactivity). It is important to identify the various negative effects that conditions due to alterations in the habenula can produce in the body.
The habenula as a protector against nicotine consumption
Currently, it has been possible to discover the implications that the habenula has on nicotine consumption. Specifically, the medial habenula circuit protects animals and presumably also humans from the consumption of high amounts of nicotine
The neurons of the medial habenula contain a special type of nicotinic cholinergic receptor. The nerve cells that express these receptors send their axons to the interpeduncular nucleus, located in the intermediate line of the midbrain. This pathway appears to inhibit the reinforcing effects of nicotine.
Processes in which the habenula is involved
The habenula presents two types of processes, normal and non-normal. Within the first presents functions related to sleep, sexual behavior, response to reward (due to its links with the limbic system), behavioral response to pain and among other functions, having a modulating function on various brain structures.
On the other hand, within non-normal processes it is related to an altered and hyperactive response in people with major depression, lower volume in people oriented to show little interest and pleasure in ordinarily pleasant things. Besides, favors excessive focus on negative aspects is related to behaviors that occur in schizophrenia, and its injury at an early age can generate symptoms and signs similar to ADHD (Attention Deficit Hyperactivity Disorder) in the individual.
Related article: “Types of ADHD (characteristics, causes and symptoms)”
Habenula and its relationships with depression
The habenula gives us clues about unpleasant events, according to research carried out by University College London in the United Kingdom. The study was published in “Proceedings of the National Academy of Sciences” and shows us for the first time that the habenula helps predict unfavorable or negative events such as painful electric shocks, suggesting a role in learning from bad or unfavorable experiences.
The research results demonstrate the link between the habenula and motivated behavior and also show how it could be related to the cause of symptoms such as low motivation, pessimism and focusing on negative experiences. Finally, understanding the habenula would help us develop better treatments to deal with depressive symptoms that are often resistant to psychological and medical treatment.
Current studies of the habenula
Nowadays, more in-depth studies are being carried out on the habenula, especially in its possible relationship with drug addiction and the persistence of aversive memories. Likewise, there are works related to depression as stated above; However, it is still important to continue expanding research to be able to know with greater precision and magnitude the effects that the habenula can have on the integral functioning of our body. That is why it would be highly recommended to promote research directed towards this field of neurosciences and biological sciences.
