The basal ganglia are a group of subcortical structures located at the base of the brain in each cerebral hemisphere. They are essentially composed of the caudate nucleus, putamen, and the globus pallidus. Many anatomists also include the substantia nigra as part of this group of grey masses. They receive myelinated axons from primary and secondary motor cortical areas of the cerebrum, sending fibers to other parts of the brain, such as hypothalamus. Blood supply: they receive oxygenated blood from the lenticulostriate arteries (also known as anterolateral central arteries), which are branches of the middle cerebral artery.
Function
They are grey nerve cell masses, whose main function is refinement or fine-tuning of cortical motor movement, especially control of the eyeball and hands. The basal ganglia also play an important role in motor learning and motivational behavior. Damage to these grey nuclei causes several movement disorders. Thus, they are involved mainly in motor control. Adequate functioning of these brain structures needs dopamine neurotransmitter at the input nuclei. Several movement disorders, such as Parkinson´s disease, chorea, and dystonia, are related to dopamine disruption or alteration.
Anatomical Description
The most conspicuous part of the basal ganglia is the caudate nucleus. It is an elongated, curved, nerve cell mass, which is in contact with the lateral ventricle. It consists of an enlarged rostral (frontal) portion, known as the head of the caudate nucleus, a short intermediate body, and a long tail, which runs backwards and then downwards into the temporal lobe, ending close to the amygdala.
The putamen is a large, round mass of neurons, which is connected to the caudate nucleus by narrow, bridging bands of grey substance. It is located medial to the insula, and it forms, together with the globus pallidus, the lentiform nucleus, which is a cone-shaped complex, with the apex pointing inwards. The putamen constitutes the outer portion, while the globus pallidus forms the inner part.
Below, location of basal ganglia in relation with the cerebral cortex. The globus pallidus is cylindrical and it lies at the center of putamen.
A transverse section of cerebrum (viewed from above) shows the three main structures that make up the basal ganglia.
