The lenticular nucleus, also known as the extraventricular nucleus of the striatum, is a brain structure that lies below and outside the caudate nucleus. This region is in the full oval center, that is, in the area of the brain that is formed by nerve fibers of white matter located between the cerebral cortex and the central gray nuclei.
This nucleus referring to the basal ganglia of the brain is characterized by originating through two other nuclei: the putamen and the globe pallidus. Thus, certain regions of these nuclei give rise to the lenticular nucleus due to the connection between them.
This article reviews the main characteristics of the lenticular nucleus. Its anatomical properties are discussed and the functions performed by this structure of the basal ganglia are explained.
characteristics
The lenticular nucleus is a structure that is part of the basal ganglia, which make up a series of nuclei or masses of gray matter.
This structure, as with the rest of the nuclei of the basal ganglia, are found at the base of the brain. Specifically, they occupy a central place in the brain, which is surrounded by ascending and descending pathways of white matter.
More specifically, the lenticular nucleus is characterized by not constituting a "proper region", but rather the conjunction of different nuclei of the basal ganglia.
In fact, the lenticular nucleus originates through the union of the globe pallidus with the putamen, so it is the physical and functional connection between these two structures that motivates the appreciation of the lenticular nucleus.
Beyond the connection between the putamen and the globus pallidus, these two structures are interconnected with the cerebral cortex, the thalamic nuclei, and the brain stem. That is, the lenticular nucleus is related to other regions of the brain.
The activities carried out by the lenticular nucleus are mainly associated with motor processes. In fact, this structure is key when it comes to starting and maintaining the body's movements.
However, the most recent research on its functioning has postulated that this nucleus of the basal ganglia could be associated with other types of activities.
Anatomy
The lenticular nucleus constitutes a structure that, visualized by a frontal cut, has a highly triangular shape. In fact, many researchers consider this nucleus as a triangular prism.
In the morphology of the nucleus, three main faces can be distinguished: a lower face, an internal face and an external face. Likewise, it has two extremities (one anterior and one posterior) and three edges.
The underside of the lenticular nucleus largely borders the oval center of the temporo-occipital lobe. Instead, in front it contacts the gray matter of the anterior perforated space and, in some regions, fuses with it.
This region of the lenticular nucleus is characterized by being obliquely crossed by the anterior white commissure. This commissure carves out a channel known as the white commissure channel.
The external face, on the other hand, is covered by a second white sheet, which separates the lenticular nucleus from the antemural and from Reil's insula.
As regards the posterior extremity of the nucleus, it constitutes a mass that becomes thinner and resolves itself into a number of longitudinal extensions. Said extensions are superimposed vertically.
The forelimb, on the other hand, stands out for being much more voluminous and presenting an irregularly rounded shape. This limb gradually fuses with the head of the caudate nucleus.
The union between the anterior extremity of the lenticular nucleus with the head of the caudate nucleus gives rise to a set in the shape of a stretched U, whose two branches are represented by the two nuclei and the middle part by the gray mass that unifies them at its anterior extremity.
Components
When the lenticular nucleus is observed from a frontal section, that is, from the front, it presents a gray mass that is crossed in its lower region by two white sheets: the internal medullary lamina and the external medullary lamina.
These two sheets are responsible for decomposing the gray mass that makes up the lenticular nucleus and constitutes three different segments. These are:
- External segment or putamen: it is characterized by presenting a more intense color and encompassing certain regions of the putamen nucleus.
- Internal segment: it differs from the external segment by presenting less coloration and constituting elements referring to the pale globe.
- Middle segment: the coloration of this component forms a middle term between that of the internal segment and that of the putamen and represents the union between the two other segments of the lenticular nucleus. This region also includes structures related to the globe pallidus.
Features
The functions of the lenticular nucleus are mainly associated with motor processes. In fact, this structure is one of the most important elements of the brain when it comes to developing movement.
This activity is carried out by all the segments that make up the lenticular nucleus, as well as by the two structures it encompasses: the putamen and the globe pallidus.
Putamen (light blue)
When it comes to performing motor processes, the lenticular nucleus is characterized by establishing a large number of connections both with the cerebral cortex and with the thalamic nuclei.
Pale balloon (light blue)
In fact, this structure establishes a bidirectional connection with the motor cortex. That is, it first receives information about the cortical regions and, later, sends these nervous stimuli back to the cortex.
In this sense, the lenticular nucleus plays a role in controlling and regulating movement. The passage of information through this structure allows adapting the information to the specific needs of each moment.
Finally, the thalamus acquires importance in these brain processes since, when the lenticular nucleus "returns" the information to the motor cortex, it does not do so directly, but sends the nerve stimuli in the first instance to the thalamic nuclei.
Subsequently, it is these subcortical structures that are responsible for transferring the information to the motor cortex and ending the process of motor activity.
References
- Anatomy diagram: 13048.000-2 ″.Roche Lexicon - illustrated navigator.
- Lanciego, José L.; Luquin, Natasha; Obeso, José A. (22 January 2017). »Functional Neuroanatomy of the Basal Ganglia». Cold Spring Harbor Perspectives in Medicine.
- Parent A (1986). Comparative Neurobiology of the Basal Ganglia.
- Percheron, G., Yelnik, J. and François. C. (1984) A Golgi analysis of the primate globus pallidus. III-Spatial organization of the striato-pallidal complex. J. Comp. 227: 214-227.
- Percheron, G; Fénelon, G; Leroux-Hugon, V; Fève, A (1994). «History of the basal ganglia system. Slow development of a major cerebral system ». Revue neurologique.