Anatomy & Organs

Thalamus – structure, function & diseases

Thalamus

The thalamus is part of the midbrain . It is made up of different core areas.

What is the thalamus

The dorsal thalamus is a part of the diencephalon . Other parts are the hypothalamus including the pituitary gland , the subthalamus and the epithalamus including the epiphysis. There is one thalamus in each hemisphere of the brain. It has a bean-shaped structure and is composed of several core areas.

These areas have a strong connection to the cortex of the cerebrum . Apart from the olfactory pathway, all of the ascending pathways important for sensory information require thalamic circuitry. For this reason, this area of ​​the brain is also called the “gateway to consciousness”.

Anatomy & Structure

Anatomically, the thalamus is located in the center of the midbrain. It is adjacent to the 3rd ventricle. The thalamus is made up of two halves. These reach the size of a pigeon egg. The area Adhaesio interthalamica usually provides a connection between the left and the right thalamus.

The thalamus consists of over one hundred core areas, also known as nuclei. These areas are divided into two groups. These are the specific and non-specific thalamic nuclei. With the specific nuclei there is a connection to the areas of the cerebral cortex that can be clearly defined. After the nuclei have received sensory and sensitive impulses from the peripheral areas, they ensure that they are passed on to the cerebrum after switching.

The most important specific nuclei include the posterior ventricular nucleus , which serves as a switching point for sensory signals for touch and depth sensitivity, and the anterolary ventricular nucleus , which processes motor signals. The nucleus mediales thalami is important for higher cognitive abilities , while the nucleus anteriores thalami plays an important role in activities of the limbic system. Other specific nuclei are the corpus geniculatum mediale , which represents an important switching point for the auditory pathway, the corpus geniculatum laterale, which performs the same function for the visual pathway, and the pulvinar. This is important for memory, perception and language.

The unspecific nuclei have only a weak or even no connection with the cerebral cortex.

Information is conveyed to them by the reticular formation , the basal ganglia , and the cerebellum ( cerebellum ). There is also a connection to the specific nuclei of the thalamus. Nonspecific nuclei include the median nuclei and the interlaminar nuclei . While the median nuclei are intimately connected to the limbic and olfactory systems, the interlaminar nuclei are important in controlling the human state of consciousness.

The non-specific nuclei have the ability to take over different areas when activated. Certain connections are important for attention to cognitive processes. In contrast, others focus on external or emotional stimuli. Furthermore, special stimuli are also sensitized. A sleeping mother can be awakened by every movement of her baby, while she does not react to a passing truck.

Function & Tasks

The term thalamus comes from the Greek. Translated, it means “bedroom” or “chamber”. However, these designations do not have much to do with the functions of the diencephalon area. The thalamus is a filter upstream of the cerebral cortex.

All information that arrives in this area is pre-processed before being sent to the cerebrum. The decision as to which incoming information is important for the body lies with the thalamus. For this purpose, the afferent (supplying) nerve cells transmit information from the organism to the thalamus. There, in the specific thalamus nuclei, a switchover to subsequent nerve cells takes place, which leads to transmission to the cerebrum.

Switching occurs through a simple processing of information, with the thalamus acting as a filter, separating unimportant information from important data. The non-specific thalamus nuclei are responsible for controlling this function. These receive their input from other areas of the brain. In this way, the decisions of the thalamus about important information are coordinated in the context of the overall physical situation.

Diseases & Ailments

Pathological damage to the thalamus can have a significant impact on the organism. The lesions primarily affect the opposite (contralateral) side of the body. This often results in ataxia , which is a movement coordination disorder. Ataxia can occur even with normal muscle strength.

Another disorder is hemiparesis . This means the incomplete paralysis of one side of the body such as hemiplegia. Stroke is one of the most common causes of hemiparesis . Another possible consequence of thalamic damage is thalamic pain, also called central pain. For example, lesions in the thalamus often result in lesions in other areas of the central nervous system (CNS), which in turn results in pseudothalamic pain.

If the nucleus ventralis posterolateralis is affected, this leads to disturbances in depth and surface sensitivity. The disorder becomes noticeable through a feeling of heaviness in the limbs. However, extensive damage to the thalamus occurs only in rare cases. However, if they do occur, the people affected suffer from sensory and motor deficits. In addition, there are psychological problems .

Other conceivable consequences of damage to the thalamus are impaired attention, sensory disturbances , changes in personality and clouded consciousness.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.