What Is The Globus Pallidus?
The globus pallidus is a nucleus located within the basal ganglia, a group of structures deep within the brain involved in motor control and movement coordination. It is located between the putamen and the internal capsule.
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The globus pallidus can be further divided into two segments: the external segment (GPe) and the internal segment (GPi). The GPe is located more centrally within the basal ganglia circuitry, while the GPi is positioned more medially.
It plays a critical role in regulating movement and is affected in various movement disorders, such as Parkinson's disease.
The globus pallidus receives input from other structures in the basal ganglia, such as the striatum, and sends output to the thalamus, which then relays information to the cortex.
Dysfunction of the globus pallidus can lead to motor abnormalities and movement disorders [1, 2, 3].
Structure of the Globus Pallidus
Globus Pallidus Internal
The globus pallidus internal (GPi) is a component of the basal ganglia, a network of subcortical nuclei involved in motor, associative, and limbic functions.
Studies have shown that GPi neurons in humans carry non-motor information and respond to reward-related stimuli and visual stimuli.
GPi is targeted in neurosurgical procedures for the treatment of movement disorders like Parkinson's disease and dystonia. It plays a role in the modulation of motor symptoms and the generation of dyskinesias. GPi also sends reward-related signals to the lateral habenula, which is associated with the limbic system [4,5].
Globus Pallidus External
The globus pallidus external (GPe) is a nucleus within the basal ganglia that plays a crucial role in motor control and movement regulation. It receives inputs from the striatum and the subthalamic nucleus, and sends outputs to various other structures within the basal ganglia.
Recent studies have revealed the heterogeneity of GPe neurons and their distinct roles in motor and nonmotor behaviors. Interestingly, optogenetic interventions targeting specific cell populations in the GPe have shown promising results in restoring movement in animal models of dopamine depletion [6, 7].
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Damage and Diseases Affecting Globus Pallidus
Damage
Damage to the globus pallidus can occur due to various causes, including cerebral palsy, carbon monoxide toxicity, opiate drug abuse, liver cirrhosis, and neurodegenerative disorders.
Studies have shown that damage to the globus pallidus is often associated with other basal ganglia structures and can lead to motor and cognitive impairments [8].
In particular, lesions of the globus pallidus (GP) can lead to various clinical features. In some cases, patients with unilateral GP lesions presented with contralateral dystonia, affecting one arm or one leg. In other cases, GP lesions resulted in parkinsonian features such as micrographia and mild dystonia in one arm [9].
Diseases
Several diseases result in changes in the globus pallidus. These include:
- Huntington's disease is a neurodegenerative disorder that affects the basal ganglia, including the globus pallidus. It is characterized by progressive movement abnormalities, such as chorea (involuntary jerking movements), as well as cognitive and psychiatric symptoms [10].
- Parkinson's disease is another neurodegenerative disorder that affects the basal ganglia, including the globus pallidus. It is characterized by motor symptoms such as tremors, rigidity, and brady kinesia (slowness of movement) [11]. Interestingly, the globus pallidus internal has been recognized as an effective therapeutic target for Parkinson's disease. Deep brain stimulation of the GPi has been shown to improve motor symptoms and reduce medication requirements in PD patients [12].
- Wilson's disease is a genetic disorder that leads to the accumulation of copper in the body, including the brain. Copper buildup in the globus pallidus can cause movement disorders, such as dystonia and tremors [13].
- Kernicterus is a condition that occurs in newborns with severe jaundice. It can lead to bilirubin deposition in the globus pallidus, resulting in movement abnormalities [14].
These are just a few examples of diseases that involve the globus pallidus and its effect on movement. Each disease has its specific features and manifestations, but it is clear that the function of the globus pallidus is in movement. It's important to consult with a healthcare professional for an accurate diagnosis and appropriate management.
Conclusion
In conclusion, the globus pallidus plays a crucial role in our motor functions, sitting at the heart of the basal ganglia's complex network. Its structure, divided into internal and external segments, helps regulate both our movements and certain non-motor processes.
As we've seen, disorders like Parkinson's and Huntington's disease, along with conditions like Wilson's disease and Kernicterus, underscore the globus pallidus's vital importance in movement coordination. Advances in medical treatments, particularly deep brain stimulation, offer hope in managing the symptoms related to its dysfunction.
This deeper understanding of the globus pallidus not only sheds light on these conditions but also opens up new avenues for exploring the intricate mechanisms of our brain.