Striatum

How is the corpus striatum formed and what does it consist of?

• Caudate nucleus (nucleus caudatus) and globus pallidus (globus pallidus) are the basic components, interconnected by numerous thin "bridges" of gray matter. On an anatomical specimen, they appear as stripes, which gave the entire structure its name.
• Internal capsule (capsula interna) — during embryogenesis, its fibers grow through the initially homogeneous basal ganglia, forming the striated appearance.
• Nucleus accumbens (nucleus accumbens) — this is the name of the ventral segments of the striatum.
• Cellular composition: the most common cell type in the striatum is GABAergic medium spiny neurons.

Where does the striatum receive information from (afferent pathways)?

The striatum receives signals from several brain structures:

• From the cerebral cortex — it receives extensive information, mainly from the motor areas of the frontal lobe (areas 4, 6aα, and 6aβ). The fibers originate from the pyramidal cells of layer V of the cortex, descend on their own (ipsilateral) side, and have a strict somatotopic organization. These pathways are glutamatergic.
• From the substantia nigra (substantia nigra) — dopaminergic fibers of the nigrostriatal pathway arrive, exerting a modulating influence.
• From the centromedian nucleus of the thalamus — excitatory pathways arrive, conducting impulses from the cerebellum and the reticular formation of the midbrain.
• From the raphe nuclei (nuclei raphes) — serotonergic fibers arrive.

Where do the signals go (efferent pathways)?

The sources of efferentation are GABAergic medium spiny neurons, which are the most common cell type in the striatum.

• To the globus pallidus (globus pallidus) — the main pathways heading to the external and internal segments are directed here. The globus pallidus receives the bulk of its afferent information specifically from the striatum.
• To the substantia nigra — additional pathways go to the pars compacta and pars reticulata.

Important: fibers running in the opposite direction — from the striatum to the cerebral cortex — presumably do not exist.

Blood supply

The blood supply to the deep brain structures has a territorial distribution:

• Middle cerebral artery (a. cerebri media) gives off deep striate branches (rami striati, or lenticulostriate arteries). They ascend vertically and supply the basal ganglia, including the putamen, globus pallidus, and caudate nucleus.
• Anterior cerebral artery supplies blood to the anterior parts of the basal ganglia.

Functions and clinical significance

The striatum, as a component of the basal ganglia, participates in motor processes, emotional expression, and the integration of sensory and motor impulses into cognitive processes.

• Parkinson's disease: the pathogenesis of the disease is associated with the death of dopaminergic neurons in the substantia nigra, which normally send fibers to the striatum. The loss of this influence leads to an increase in the inhibitory effect of the striatum on the external globus pallidus (GPe). This triggers a cascade of reactions: hyperactivity of the subthalamic nucleus and internal globus pallidus, excessive inhibition of the thalamus and a decrease in its excitatory influence on the cortex, causing hypokinesia.
• Psychiatry: dysfunction of the neural networks connecting the striatum, thalamus, limbic system, and prefrontal cortex is associated with emotional and behavioral disorders, including anxiety, depression, apathy, and hallucinations.
• Infectious lesions: in epidemic typhus, typhus granulomas — Popov-Fraenkel-Davydovsky nodules — form in the striatum, along with the medulla oblongata and cortex. Central nervous system involvement is accompanied by the development of serous meningoencephalitis, edema, swelling of brain tissue, and hemorrhages.

Class and exam questions

What else to study on this topic

• Basal ganglia and their connections
• Substantia nigra
• Globus pallidus
• Internal capsule (Capsula interna)
• CNS neurotransmitters: GABA and glutamate

Other topics in the "Anatomical Structures" section

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