Basal ganglia nuclei lateral view

The basal ganglia, from the point of view of strict neu-roanatomy, consist of three major nuclei in each of the hemispheres. (The reader is reminded that this illustration has been enlarged from the previous figure, and that these structures are located within the forebrain.)

• The globus pallidus

• The caudate nucleus is anatomically associated with the lateral ventricle and follows its curvature. It is described as having three portions (see Figure 25):

• The head, located deep within the frontal lobe

• The body, located deep in the parietal lobe

• The tail, which goes in to the temporal lobe

The basal ganglia are shown in this illustration from the lateral perspective, as well as from above, allowing a view of the caudate nucleus of both sides. The various parts of the caudate nucleus are easily recognized — head, body, and tail. The head of the caudate nucleus is large and actually intrudes into the space of the anterior horn of the lateral ventricle (see Figure 27 and Figure 28A). The body of the caudate nucleus tapers and becomes considerably smaller and is found beside the body of the lateral ventricle (see Figure 29 and Figure 76). The tail follows the inferior horn of the lateral ventricle into the temporal lobe (see Figure 76). As the name implies, this is a slender extended group of neurons, even more difficult to identify in sections of the temporal lobe (see Figure 74).

The lentiform or lenticular nucleus, so named because it is lens-shaped, in fact is composed of two nuclei (see next illustration) — the putamen and the globus pallidus.

The lentiform nucleus is situated laterally and deep in the hemispheres, within the central white matter. Sections of the brain in the horizontal plane (see Figure 27) and in the coronal (frontal) plane (see Figure 29) show the location of the lentiform nucleus in the depths of the hemispheres, and this can be visualized with brain imaging (see Figure 28A and Figure 28B).

The lentiform (lenticular) nucleus is only a descriptive name, which means lens-shaped. The nucleus is in fact composed of two functionally distinct parts — the putamen laterally, and the globus pallidus medially (see Figure OA, Figure 27, and Figure 52). When viewing the basal ganglia from the lateral perspective, one sees only the putamen part (see Figure OL and Figure 73).

The caudate and the putamen contain the same types of neurons and have similar connections; often they are collectively called the neostriatum. Strands of neuronal tissue are often seen connecting the caudate nucleus with the putamen. A very distinct and important fiber bundle, the internal capsule, separates the head of the caudate nucleus from the lentiform nucleus (see next illustration). These fiber bundles "fill the spaces" in between the cellular strands.

Additional Detail

The inferior or ventral portions of the putamen and globus pallidus are found at the level of the anterior commissure. Both have a limbic connection (discussed with Figure 80B). The amygdala, though part of the basal ganglia by definition, has its functional connections with the limbic system and will be discussed at that time (see Figure 75A and Figure 75B).

NOTE on terminology: Many of the names of structures in the neuroanatomical literature are based upon earlier understandings of the brain, with terminology that is often descriptive and borrowed from other languages. As we learn more about the connections and functions of brain areas, this terminology often seems awkward if not obsolete, yet it persists.

The term ganglia, in the strict use of the term, refers to a collection of neurons in the peripheral nervous system. Therefore, the anatomically correct name for the neurons in the forebrain should be the basal nuclei. Few texts use this term. Most clinicians would be hard-pressed to change the name from basal ganglia to something else, so the traditional name remains.

Caudate n. (body)

Caudate n. (head)

Lentiform n. (putamen & globus pallidus)

Caudate n. (body)

Caudate n. (head)

Lentiform n. (putamen & globus pallidus)

Lentiform Body

Gray matter connecting caudate with putamen

Caudate n. (tail)

Anterior commissure

Gray matter connecting caudate with putamen

Caudate n. (tail)

Anterior commissure

Amygdala

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