Lateral globus pallidus
|Lateral globus pallidus|
Lateral globus pallidus (GPE) seen in 2nd image from the left
|Latin||Globus pallidus lateralis,
globus pallidus externus
|NeuroLex ID||Globus pallidus external segment|
|Anatomical terms of neuroanatomy|
The lateral globus pallidus (or external globus pallidus, GPe) combines with the medial globus pallidus to form the globus pallidus, an anatomical subset of the basal ganglia. Globus pallidus means "pale globe" in Latin, indicating its appearance. The lateral globus pallidus is the segment of the globus pallidus that is relatively further (lateral) from the midline of the brain.
The lateral globus pallidus contains GABAergic neurons, which allow for its inhibitory function. The lateral globus pallidus' GABAergic neurons extend axons to the subthalamic nucleus (in the dicencephalon), the striatum, medial globus pallidus and substantia nigra pars reticulata.
GPe is particular in comparison to the other elements of the set by the fact that it does not work as an output base of the basal ganglia (not sending axons to the thalamus) but as the main regulator of the basal ganglia system. It is sometimes used as a target for deep brain stimulation as a treatment for Parkinson's disease.
Indirect Striatopallidal Pathway
The basal ganglia functions to tonically inhibit movement, mainly in the absence of motor cortex command, via GABAergic inhibition of the ventral lateral nucleus and ventral anterior nucleus of the thalamus, as well as the superior colliculus and mesopontine tegmentum of the brain stem. When movement is required, the cerebral cortex sends commands to the striatum, which directly inhibits the medial globus pallidus and substantia nigra pars reticulata, decreasing thalamus and brainstem inhibition. As the pathway from the striatum to the medial globus pallidus is monosynaptic (containing one synapse), it is called the Direct Striatopallidal Pathway.
The Indirect Striatopallidal Pathway, which contains the lateral globus pallidus and the subthalamic nucleus, functions to modulate the effects of the Direct Striatopallidal Pathway. The lateral globus pallidus acts as an inhibitory "control device", adjusting subthalamic nucleus neuronal activity via GABAergic output.
When movement adjustment is required, striatal inhibitory GABAergic axons are sent to the lateral globus pallidus, decreasing inhibition of the subthalamic nucleus. The subthalamic nucleus' glutamatergic neurons then stimulate the Medial globus pallidus and substantia nigra pars reticulata.
This multisynaptic indirect striatopallidal pathway allows for regulated excitatory input from the subthalamic nucleus to the Medial globus pallidus and substantia nigra pars reticulata. This combines with Direct Striatopallidal Pathway inhibition in the medial globus pallidus, allowing for fine tuned basal ganglia output, and more controlled movement.
Lateral globus pallidus dysfunction has been observed in the following conditions:
- Parent, André; Hazrati, Lili-Naz (1995-01-01). "Functional anatomy of the basal ganglia. I. The cortico-basal ganglia-thalamo-cortical loop". Brain Research Reviews. 20 (1): 91–127. doi:10.1016/0165-0173(94)00007-C.
- Parent, André; Hazrati, Lili-Naz (1995-01-01). "Functional anatomy of the basal ganglia. II. The place of subthalamic nucleus and external pallidium in basal ganglia circuitry". Brain Research Reviews. 20 (1): 128–154. doi:10.1016/0165-0173(94)00008-D.
- Hegeman, Daniel J.; Hong, Ellie S.; Hernández, Vivian M.; Chan, C. Savio (2016-05-01). "The external globus pallidus: progress and perspectives". European Journal of Neuroscience. 43 (10): 1239–1265. doi:10.1111/ejn.13196. ISSN 1460-9568. PMC . PMID 26841063.
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