Forebrain

Synonym

ProsencephalonThe forebrain is a part of the brain and thus belongs to the central nervous system. It includes the diencephalon (diencephalon) and the cerebrum (telencephalon). These emerge from the forebrain vesicle during the embryonic development phase of the brain. The forebrain has a multitude of functions, the cerebrum is essential for numerous processes such as motor functions, vision, hearing and many others. The diencephalon, which contains the hypothalamus and pituitary gland, plays a central role in the hormone regulatory circuit, among other things.

Interbrain

Synonym: Diencephalon The diencephalon is the lower (caudal) border of the midbrain (mesencephalon), which is part of the brain stem. On the top it borders on the cerebrum, although an exact demarcation is difficult to make here. The diencephalon consists of thalamus, epithalamus, subthalamus and hypothalamus.

Thalamus

Anatomy & Function: The thalamus is present in pairs, i.e. on both sides, and its inner wall (medial) delimits the third ventricle, one of several cavities of the brain filled with cerebrospinal fluid (liquor). The outer wall (lateral) of the thalamus borders the internal capsule, through which numerous nerve fiber bundles run on their way to the cerebrum or from the cerebrum to the periphery. The thalamus is composed of numerous nerve cell nuclei, which are connected to each other by nerve fibers.

There are also numerous nerve fiber connections between the thalamus nuclei and the cerebrum. Almost all sensory or sensitive pathways that run from the periphery into the cerebrum first project into the thalamus and from there into the cerebrum. This is why the thalamus is sometimes referred to as the “gateway to the cerebral cortex”.

Many of the human sensory impressions, such as seeing (via the Corpus geniculatum laterale) and hearing (via the Corpus geniculatum mediale), are integrated and pre-sorted in the thalamus in order to avoid sensory overload of the cerebrum. If they are processed in the thalamus, they reach the cerebrum and are only then consciously perceived. The thalamus also plays its part in the processing of motor impulses.

It receives information from the cerebellum and the basal ganglia, among others, which play a decisive role in the coordination of movements. Furthermore, the thalamus plays an important role in the state of activity, i.e. tiredness or sleep as well as alertness and excitement and directed attention. Clinical reason: Damage to the thalamus can result in various symptoms.

Usually, a lesion of the thalamus on one side affects the other half of the body. This is due to the fact that almost all the fibers that run from the periphery to the center or vice versa cross over to the opposite side. Thus, a touch of the right hemisphere of the body projects into the left hemisphere of the brain. A movement that is planned in the left cortex ends up in the right hemisphere. Depending on the extent and localization of the damage to the thalamus, hemiplegia, sensitivity disorders, hemiplegia, movement restlessness, pain without recognizable pain stimulus and disturbances of consciousness can occur.