Lentiform nucleus

The lentiform nucleus is a lens-shaped mass of grey matter forming part of the basal nuclei (basal ganglia). It lies lateral to the internal capsule and consists of two main components:

• Putamen – the larger, lateral component.

• Globus pallidus – the medial component, divided into external (GPe) and internal (GPi) segments.

Medially, the lentiform nucleus is related to the internal capsule, which separates it from the caudate nucleus and thalamus.

Laterally, it is separated from the claustrum by the external capsule; farther laterally lie the extreme capsule and insular cortex.

Striatum

Functionally, the lentiform nucleus is not a single homogeneous nucleus. The putamen is closely associated with the caudate nucleus and together they form the striatum, the major input region of the basal ganglia.

Pallidal circuitry

The globus pallidus part of the lentiform nucleus, forms a major part of the pallidal circuitry, with the GPi serving as an important output component. Through interconnected basal ganglia circuits, these structures contribute to the selection, initiation and scaling of voluntary movements and suppression of unwanted motor activity.

Clinical correlates

Dysfunction of circuits involving the putamen and globus pallidus contributes to movement disorders. In Parkinson disease, loss of nigrostriatal dopaminergic input alters basal ganglia activity and produces bradykinesia and rigidity, whereas degeneration of striatal neurons in Huntington disease contributes to excessive involuntary movements such as chorea.