The midbrain is divided into thalamus, epithalamus, subthalamus, metathalamus and hypothalamus. Read more about it!


The diencephalon (Diencephalon), which lies between the cerebrum (brain) and the midbrain. It performs extremely diverse and important tasks: it is part of the brainstem, the diencephalon acts as a "gateway to consciousness," is important for endocrine and vegetative control, affects the sleep-wake cycle, and more. Read all important information about the diencephalon: function, distribution, disorders!

What is the diencephalon?

The diencephalon develops during embryonic development from a lower extension of the forebrain vesicle of the neural tube. The cavity, which surrounds the interbrain vesicles, then forms in the course of the inter-brain part of the third ventricle, which he encloses; the thickened sidewalls become the thalamus (visual hillock because it has a relation to the central visual pathway) and the pallidum of the lens nucleus (belongs to the basal ganglia).

The diencephalon is divided into five areas:


The thalamus is a ganglia mass that is the actual gateway to consciousness. Read more about this part of the diencephalon in the article Thalamus.


Below the thalamus lies the hypothalamus. Find out more about him in the article Hypothalamus.


The epithalamus is located in the posterior part of the diencephalon and above the thalamus. It is composed, among other things, of the pineal gland (epiphysis) and the habenulae (epiphyseal stems), which connect the epiphysis with the thalamus.

Another area of ​​the epithalamus contains numerous nuclei, of which seven nuclei on both sides receive afferents from the retina (retina of the eye).


The subthalamus consists primarily of the subthalamic nucleus and the pallidum - two basal ganglia that belong to the extrapyramidal motor system.


The metathalamus includes the two knees (corpus geniculatum mediale et lateral).

What is the function of the diencephalon?

The diencephalon fulfills a variety of tasks in its various areas:

The Thalamus 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. He decides which sensory impressions from the environment and the organism should penetrate consciousness.

The hypothalamus controls the endocrine functions and the production of neurohormones. Respiratory, circulatory, metabolic, food and fluid intake, body temperature, sexual behavior and sleep-wake rhythms are regulated in this interbrain region. All the emotions associated with these multiple functions are also anchored in this area of ​​the diencephalon.

The pineal gland as part of the epithalamus in the posterior part of the diencephalon produces the tissue hormone melatonin. The production is subject to a daily rhythm and controls the day-night rhythm and also a seasonal rhythm. Kernels in habenulae are switching stations for the olfactory system, which connects the olfactory brain to the brain stem.

The nucleus of the epithalamus receives afferents from the retina of the eye (retina). He ensures that the pupils narrow in the light of incidence reflector.

The subthalamus is primarily responsible for the control of gross motor skills. The subthalamic nucleus communicates with the pallidum and receives from it signals which have a movement-inhibiting function.

Neurons, coming from the cochlear dorsal nucleus, run across the rhomboid pit to the medial cleft of the knee, and the central auditory pathway moves from here to the auditory cortex. All visual and hearing impressions are switched in the two cusps of the interphalbum on the way to the visual cortex and auditory cortex. The function of these switching cores is, in particular, to modify the continuity of incoming excitations in such a way that - with concentrated attention - some sensory impressions are perceived more strongly and others less.

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Where is the diencephalon?

Between the two frontal lobes (frontal lobes) and the two temporal lobes (temporal lobes) of the cerebrum and the front edge of the bridge (pons) is the lower part of the diencephalon, which rests on the middle fossa. In front in the middle, between the two brain legs and at the base of the brainstem, there are two hemispheres, (Corpus mamillare).

The epithalamus, the posterior part of the diencephalon, lies directly on the thalamus.

What problems can the diencephalon cause?

A diencephal-autonomic crisis is characterized by atypical epileptic seizures caused by diseases of the hypothalamus.

Gliomas (emanating from the cell tissue of the nervous system tumors) in the diencephalon cause a strong mental slowing, loss of interest by a reduction of the emotions and an increased need for sleep.

Damage to the subthalamic nucleus in the subthalamus leads to the clinical picture of ballism. It is characterized by rapid, spontaneous, hurling movements of the extremities. The disorder usually occurs only on one side, on the opposite side of the injury (hemiballism). Dysphagia and speech disorders such as repetition of words and phrases, slurred speech also indicate a disturbance in this area.

The electrical stimulation of the subthalamic nucleus in the subthalamus is used therapeutically to alleviate the symptoms of Parkinson's disease.

A failure of the pallidum in the thalamus in diencephalon causes muscle stiffness and associated with a reduction in motor skills. Diseases that underlie such a disorder are Parkinson's disease, Littlesche's disease and Wilson's disease.

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