Corpus: Striatum

The striatum is an important core area of the forebrain that belongs to the basal ganglia. It fulfils a variety of tasks in the context of cognition, motivation and the planning of movement sequences.

The striatum is the largest single structure of the basal ganglia. Functionally and on the basis of its connections, it can be differentiated into a ventral and a dorsal part.

The ventral striatum consists of the nucleus accumbens and the olfactory tubercle. Together with the nucleus basalis and the centromedial amygdala, it is also summarised as the substantia innominata. This part is associated with the limbic system.

The dorsal striatum is made up of the caudate nucleus and the putamen. They form a unit in early embryonic development. In the further course of brain development, they are then separated by the ingrowth of the projection pathways of the internal capsule.

Phylogenetically, the striatum is divided into an older and a younger part:

• Palaeostriatum: developmentally older part
• Neostriatum: developmentally younger part

Histologically - especially in the dorsal striatum - an organisation of the tissue into striosomes and matrisomes can be traced using immunological staining techniques.

The most common cell type (approx. 95%) of the striatum are the medium-sized spine-bearing projection neurones (MSNs).

The striatum receives excitatory (glutamatergic) fibres mainly from the cortex. Dopaminergic fibres of the substantia nigra (pars compacta) act both excitatory (D1) and inhibitory (D2) via various dopamine receptors. Via the efferent fibres, the striatum inhibits the globus pallidus via the neurotransmitter GABA and the substantia nigra via a negative feedback connection.

The exact function of the striatum has so far (2023) only been partially clarified. The ventral striatum, especially the nucleus accumbens, fulfils a variety of tasks in the context of cognition, motivational processes and the reward system. The dorsal striatum, on the other hand, plays a major role in the planning and inhibition of movement sequences and in executive functions.

The interaction between the striatum and the prefrontal cortex is particularly relevant for behaviour control in the maturing brain.

Degeneration or atrophy of the striatum leads to movement disorders such as hyperkinesis, e.g. in Huntington's disease. In Parkinson's disease, the dopaminergic innervation of the dorsal striatum is lost, which leads to dyskinesia.