Putamen

At a glance

English

Putamen

Latin (TA2)

Putamen

System

Brain and spinal cord

Region

Head

Side

Paired, left and right

About the putamen

The putamen, whose Latin name refers to a nut shell, is a mass of grey matter low in the forebrain, deep to the insula. It is the most lateral of the basal nuclei. On its outer side the thin external capsule separates it from the claustrum and, beyond that, the insula; on its inner side lies the globus pallidus, and together the two form the lens-shaped lentiform nucleus. The internal capsule runs along the medial side of the lentiform nucleus and divides it from the caudate nucleus and thalamus.

Although the internal capsule separates them, the putamen and the caudate nucleus are built of the same cells and circuits and together make up the dorsal striatum. Grey bridges of tissue cross the internal capsule between them, giving the striped look that names the striatum. Most of its neurons are medium spiny cells that use GABA, with enkephalin or substance P; scattered large interneurons use acetylcholine.

The striatum is the main entrance to the basal ganglia. The putamen receives excitatory fibres from wide areas of cortex, especially the motor, premotor and somatosensory areas, arranged as a body map, and from the centromedian and parafascicular thalamic nuclei. Dopamine-containing fibres from the pars compacta of the substantia nigra modulate its activity. Its output passes to both segments of the globus pallidus and to the substantia nigra, forming the direct and indirect pathways that loop back through the thalamus to the cortex. Through these loops it helps prepare and execute movements, set their size and sequence, and learn habits and skills by reinforcement.

In Parkinson's disease the loss of nigral dopamine is greatest in the putamen, and this underlies slowness and stiffness of movement. Huntington's disease, Wilson's disease and kernicterus also affect the striatum. The lenticulostriate arteries that supply the putamen are a common site of hypertensive haemorrhage, which can spread into the internal capsule and cause a dense hemiplegia.

Function and supply

Function

Takes in motor and sensory cortical signals and, through basal ganglia loops back to the cortex, helps prepare, scale and sequence movements and form learned motor habits.

Blood supply

Lateral lenticulostriate branches of the middle cerebral artery; its front part also from the medial striate (recurrent) artery of the anterior cerebral artery.