Basal Ganglia

Finally, we now cut the cerebrum not with the length of the interhemispheric cleft, but rather in the middle of it transversely parallel to the forehead (frontal cut). In this incision, too, it is noticeable that some grey matter is embedded in the white matter of the cerebrum, which therefore does not belong to the cortex. The old anatomists called some of these nuclei “basal ganglia” and in the course of time this term was always extended for functional reasons.

Today, the striatum with nucleus (Ncl.) caudatus and putamen, the pallidum, the Ncl. subthalamicus and the substantia nigra are mostly counted among them.

Striatum and pallidum are located laterally of the thalamus of the diencephalon, the ncl. subthalamicus (as the name suggests) is located below the thalamus, while the substantia nigra is located far away in the midbrain. The exact interconnections of these areas and their integration into the rest of the brain fill entire textbooks; we reduce here to a practical level.

In their entirety, the basal ganglia control the extent, force, direction and speed of a movement that is still in the planning stage. What is special about this, however, is that they simultaneously evaluate the action, i.e. whether or not it could be useful in the overall context or whether it is socially acceptable at all. One could say that they are also an extended arm of their own value concepts, which can put the brakes on inappropriate behavior.

Based on these considerations, it is not surprising that some parts of the basal ganglia are important members of the motivation circuit. As such, they are constantly informed of any rewards that may be forthcoming or unwillingness in the absence of rewards, which they take into account in their processing of a movement. Especially when it comes to addiction as an extreme form of reward, they play a major role. In the planning of a movement, the basal ganglia are one of the three main paths of information flow, which begins with the will of an arbitrary movement in the limbic. Typical diseases that are associated with a disturbance of the Basal Ganglia are Parkinson’s disease and choreatic diseases such as Huntington’s disease.