Thalamus

The thalamus is part of the diencephalon and acts as a "gateway to consciousness". Read more about thalamic function and anatomy!

Thalamus

Of the thalamus or Sehhügel is a core area of ​​the Zwischenhirns. He is the collection point for all sensory impressions with the exception of the sense of smell, which are switched here on the way to the cerebral cortex - so all impressions of seeing, hearing, feeling and the temperature and pain sensation. The thalamus is therefore also called the "gate to consciousness". Read all about the thalamus: function, anatomy and important disorders!

What is the thalamus?

The thalamus forms the posterior surface of the diencephalon. It consists of gray and white matter, the gray matter being divided by thin sheets of white matter into numerous nuclei (accumulations of nerve cell bodies) - the thalamic nuclei.

The thalamus has an anterior pole in the direction of the caudate nucleus (one of the basal ganglia), which houses the anterior main nucleus of the thalamus (anterior nucleus of the thalamus). The rear pole points down the back and forms the pad (Pulvinar thalami). On the lateral side of the pulvinar is an elevation, lateral geniculate body (lateral knee-bumps), and below the anterior edge of the corpus geniculatum mediale (the middle knee-bump).

The lateral surfaces of the thalamus border on the internal capsule. This is the inner capsule of the brain, an area of ​​white matter where projection fibers run up and down from the cerebral cortex to the bridge, medulla oblongata, and spinal cord. The anterior surface is fused with the hypothalamus.

The thalamus has a thalamic radiation (Radiationes thalamicae) radiating laterally and forward. This is also called staff wreath of the thalamus and consists of double-stranded fiber tracts through which the thalamus is connected to the cerebral cortex.

What is the function of the thalamus?

The thalamus is the gateway to consciousness. It acts as a filter and distributor of incoming information. Here it is decided which sensory impressions from the environment and the organism should penetrate into the consciousness and which are then also forwarded to the appropriate processing centers. All sensory impressions of feeling, seeing and hearing - but not of smell - are transmitted through the thalamus.

The thalamus nuclei in turn accommodate smaller nuclei and areas with different functions. In the middle and posterior core groups of the thalamic nuclei, all somatosensory and sensory pathways (with the exception of the olfactory tracts), which come from the periphery and move to the cerebral cortex, are switched over. All connections are double-barreled with the corresponding bark fields. This makes it possible through concentrated attention to perceive different sensory impressions to varying degrees: strong, low or almost nonexistent.

Visual and auditory impressions are switched over in cores of the metathalamus (lateral geniculate and medial) on their way to the visual cortex and auditory cortex.

The excitation of the anterior core groups of the thalamic nuclei does not occur (like those of the middle and posterior ones) over the periphery, but via the pallidum (a main ganglion), the cerebellum, and the midbrain. These thalamic nuclei communicate with the motor and premotor bark and can influence movements.

Affective and instinctual excitations, emotional feelings are switched over in the thalamic nuclei and forwarded to the corresponding bark areas.

Taste information is brought together via the taste kernel and passed on via the thalamus to the taste bark.

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Where is the thalamus?

The thalamus is located in the midbrain, which connects to the brain stem. Its nuclear mass lies on both sides of the third brain ventricle and is covered by the two cerebral hemispheres.

What problems can the thalamus cause?

The so-called thalamic syndrome (Déjerine-Roussy syndrome) arises because a blood clot obstructs an important vessel of the thalamus (such as the thalamostriata) (thrombosis). The result is a failure of the thalamus with visual and sensory disturbances, hemianopsia (half-side blindness), a strong excitability of the reflexes as well as a reduced sensitivity of the skin and a disturbance of the deep-sensibility.

Generally, sensory disorders with reduced sensitivity, hypersensitivity to all sensory stimuli (with an increased threshold), sensory disturbances, and severe central pains in the disorder side all point to disorders in this brain region. Also, motor disorders with rigid facial muscles and hyperkinesias (forcible movements of the hands and fingers) and mental disorders with decreased attention, irritability, impatience, and aggravation may be due to damage or disease in the area of thalamus point out.


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