Anatomical Parts of the Caudate Nucleus
The nucleus has a curved shape that mirrors the contour of the lateral ventricle, resulting from the rotation of the telencephalon during embryogenesis. Due to this C-shape, coronal sections display the structure in two distinct, widely separated areas.
Anatomically, it is divided into three parts:
- Head (caput): The rostral portion, which forms the lateral wall of the anterior horn of the lateral ventricle. Rostrally, the head is covered externally by the putamen (putamen).
- Body (corpus): Extends along the body of the lateral ventricle, contributing to its lateral wall.
- Tail (cauda): Descends into the temporal lobe, forming the roof over the inferior horn of the lateral ventricle. It extends anteriorly to reach the amygdala (corpus amygdaloideum), which lies in the anterior pole of the inferior horn.
Topography and Embryonic Development
During embryogenesis, the caudate nucleus develops from the ganglionic eminence, a derivative of the ventral telencephalon. Together with the putamen, it forms the phylogenetically newer structure known as the neostriatum. Through the evolution and expansion of the cerebral cortex, the neostriatum enlarged significantly, reaching its peak development in higher mammals and humans. <div></div>
The caudate nucleus and globus pallidus (globus pallidus) are interconnected by numerous fine bridges of gray matter. On anatomical sections, these appear as stripes, grouping these nuclei under the collective term corpus striatum (corpus striatum). This striated appearance forms during embryogenesis when fibers of the internal capsule (capsula interna) grow through the initially homogeneous basal ganglia. <div></div>
Topographically, the nucleus arches around the thalamus and the lentiform nucleus. The terminal stria (stria terminalis), which originates from the amygdala and carries its efferent fibers, runs within the sulcus between the thalamus and the caudate nucleus.
Functions and Motor Hierarchy
The caudate nucleus is an integral component of the motor system. The basal ganglia form complex feedback regulatory loops with the motor areas of the cerebral cortex.
- Motor Control: The basal ganglia exert inhibitory or disinhibitory influences on the thalamus, which acts as a relay station between the basal ganglia and the cortex. This mechanism "permits" or "prohibits" the execution of specific motor programs in the cortex.
- Tone Regulation: The basal ganglia participate in initiating and coordinating complex motor patterns and regulating baseline muscle tone.
- Protective Function: Along with the subthalamic nucleus and parts of the pons, the caudate nucleus helps shield the brain from excessive neural excitation.
During evolution, the cortex developed a new motor (pyramidal) system that progressively exerted control over older centers, including the neostriatum. In humans, motor function relies entirely on the integrity of the pyramidal system; older subcortical centers cannot fully compensate for damage to newer cortical-spinal pathways.
Blood Supply
The striate branches of the middle cerebral artery (a. cerebri media) supply the basal ganglia, including the caudate nucleus. These deep perforating branches ascend vertically to nourish the major portion of the striatum. The anterior regions of the basal ganglia also receive blood from the anterior cerebral artery territory.
Clinical Significance
Damage to the basal ganglia results in an excess or deficit of motor output, as well as pathological alterations in muscle tone.
- Parkinson's Disease: The most common pathology affecting the basal ganglia, characterized by the classic clinical triad: rigidity, akinesia (or bradykinesia), and resting tremor.
- Synkinesias: In cases of spastic paralysis, involuntary associated movements known as synkinesias may appear in the paralyzed limbs, generated by phylogenetically older motor centers.
- Epilepsy: Certain types of epileptic activity are hypothesized to involve dysfunction of the brain's protective gating structures, including the caudate nucleus.