We analyze the functioning of this complex structure of the brain.
Language, memory or learning, events that occur in our day to day occur here. But it also has the objective of maintaining control that the rest of the organs work correctly. That is why it is possibly the most important system for the maintenance of life.
One of the organs that make up the CNS is the brain, which is divided into many regions. If we talk about which can have a great relevance in functions, surely when mentioning the thalamus we are not mistaken . From the Greek thalamos , which means internal chamber, it indicates its privileged place in the organs, since it is located in the center of it, which allows it to communicate with all the regions.
thalamus anatomy
The thalamus is two oval and symmetrical structures, composed of gray matter, that is, neuron bodies . These nuclei are not completely separated, since they are linked by interthalamic adhesion, which allows communication between them.
For its part, the thalamus is part of the diencephalon , specifically occupies 80% of this region, along with the hypothalamus and other nuclei . It is the lower part of the cerebral cortex and it is above the brainstem. Due to its position, it is perfect to act as a relay station for nerve impulses before reaching the brain.
thalamus structure
There are many criteria to divide this region into different nuclei, either due to their anatomical position, their functions, or their evolutionary perspective. Very difficult to have a consensus for which is the best way to separate the neuron bodies, since about 50 different nuclei have been found, for which I will mention their anatomical-functional position:
- Anterior nuclear group : connects with the hypothalamus and the limbic system. It is involved in emotions, alarm state regulation and memory.
- Dorsomedial nucleus : connects with the cerebral cortex, the limbic system, and the basal ganglia. It acts on emotions, learning, memory, the degree of consciousness and cognition.
- Lateral nuclear group : communicates with the superior quadrigeminal tubercle, limbic system, and cerebral cortex. Participates in the expression of emotions and sensory integration.
- Posterior nuclear group – connects the cerebellum and the cerebral cortex. Involved in motor functions and sensory information.
- Midline nuclei : Communicate with the cerebellum, basal ganglia, and cerebral cortex. It acts on pain, motor and sensory function and awakening.
- Intralaminar nuclei : Form a thin lamina near the third ventricle. It is presumed that it participates in memory and olfaction.
- Reticular nuclei : surround the lateral part of the thalamus. Its function is to integrate and control the other nuclei of the region.
As can be seen, this region connects with many other areas of the brain and participates in many functions. It is no coincidence that his position in this body is specifically the center.
The neurons of the thalamus
Although the thalamus, as we have seen before, is made up of different nuclear groups that are involved in different functions and communicate with different regions, but all of them are neurons and glial cells. If we look from a functional point of view, we can distinguish between two types of neurons:
- Projection neurons : They are the neurons in charge of transmitting information out of the thalamus and represent 75% of it.
- Local interneurons : They are responsible for the information received to be processed and transmitted to the projection neurons. Interneurons are only connected with others that are involved in the same process. It represents only the remaining 25%.
Functions performed
Initially, the thalamus had been assigned the function of a simple relay point for nerve signals arriving from other parts and transmitting them to the cerebral cortex. This traditional vision is no longer valid, since it has been observed that the thalamus actively participates in many processes, proof of this is that it not only sends information to the cortex, but also receives it. Now we will see some of its functions .
1. Senses
One of the most studied and detailed functions of the thalamus is possibly its role in the transmission of the senses. Except for the olfactory, which goes directly to the temporal cortex, the others go through the thalamus.
Although at first it was thought that the thalamus was simply a point of passage for sensory signals, in reality it does much more and performs an integration and “filtering” of this information. In other words, prioritize the information that is of interest at that moment. An example is when you listen to your favorite music, it focuses on the auditory sense, and the rest of the senses go into the background, so we relax.
2. Pain
The sensation of pain perceived by the nociceptors (sensory neurons) is sent to the CNS passing through several stations, one of which is the thalamus. In addition to processing the information received, it also modulates the intensity of the pain. This is visible in thalamic syndrome, which occurs when the thalamus is damaged, producing spontaneous attacks of great intensity.
3. Sleep-wake cycle
The sleep period is another important phenomenon in which many regions of the brain participate, including the thalamus. Specifically, it has a role in establishing the NREM phase or deep sleep. In severe familial insomnia, a prion disease (that is, caused by a prion), which makes it impossible to start the NREM phase, along with difficulties in the REM phase, where the most affected region is the thalamus. For this reason, this region began to be observed as it acts in the conciliation of slow sleep.
4. Spotlight
The thalamus, thanks to the multitude of connections it presents and the information it receives, actively participates in where to focus attention. In short, as happens with the senses, you can prioritize the sensory information that you see as key to reaching the goal and minimize the others that could act as a distraction, as well as direct which regions of the cortex are activated and which are not, all with the purpose to fulfill the task that the being has proposed.
Giving a drastic example, in the case of an explosion in the distance, our attention will be focused on the noise that has occurred (prioritizes the auditory and visual sense), and possibly by understanding the situation, we will look for a place to hide or get away from the point that we consider dangerous at that moment (mechanism of locomotion).
5. Memory
It is not surprising that with the information that reaches the thalamus, it was not involved in any way in it. It has been seen that damage to this region generates problems in retaining long-term memory and temporary disorganization of events. But it is a field that continues to be studied how this region participates.
6. Language
Language is a complex process that occurs in the brain, involving a large number of regions (such as Broca’s or Wernicke’s area), including the thalamus. There is strong evidence that this area is involved in the motor aspects of speech (breathing rhythms for example), in symbolic thought and in the very use of words (coding and decoding).
7. Emotions
Although the hypothalamus and the amygdala mainly act in this phenomenon , they send their information to the thalamus, which in turn transfers it to the prefrontal lobe, so it is involved in the integration of emotional information.
conclusion
Due to its privileged position and being part of the diencephalon, the thalamus is the center through which almost all the information received by the brain passes .
At first it was thought that it simply acted by amplifying the signal, as if it were a relay station, but over time the idea that it interacts and participates in how this signal is transmitted has been expanding.
It is logical that it participates in many phenomena that occur in the brain, such as memory, encoding of the senses or sleep, due to the amount of information that passes through it. The thalamus could be said to be the “centre of the brain.”
Bibliographic references
- G. Tortora and B. Derrickson (2011) “Principles of Anatomy and Physiology” (11th ed.). Pan American Publisher.
- MV Perea and V. Ladera (2004) “The thalamus: neurofunctional aspects” https://www.researchgate.net/publication/8606530_Neurofunctional_aspects_of_the_thalamus
- MS Nadal and Y. Amarillo (2018) “The thalamus in the center of attention” https://www.researchgate.net/publication/332971067_El_talamo_en_el_centro_de_la_atencion
- FJ Cudeiro-Mazaira and C. Rivadulla (2002) “The thalamo: a dynamic door to perception”. https://www.researchgate.net/publication/267939017_El_talamo_una_puerta_dinamica_a_la_percepcion
- J.Mª. Pedrajas Navas and AM Molino González (2008) “Neuromedical bases of pain”. http://scielo.isciii.es/scielo.php?script=sci_arttext&pid=S1130-52742008000300002
- JL Velayos, FJ Moleres, AM Irujo, D. Yllanes, B. Paternain (2007) “Anatomical Bases of Sleep”.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.