Theexternal globus pallidus(GPeorlateral globus pallidus) combines with theinternal globus pallidus(GPi) to form theglobus pallidus,an anatomical subset of thebasal ganglia.Globus pallidusmeans "pale globe" in Latin, indicating its appearance. The external globus pallidus is the segment of theglobus pallidusthat is relatively further (lateral) from the midline of the brain.
| External globus pallidus | |
|---|---|
 External globus pallidus (GPe) seen in 2nd image from the left | |
| Details | |
| Part of | Globus pallidus |
| Identifiers | |
| Latin | globus pallidus externus, globus pallidus lateralis |
| Acronym(s) | GPe |
| NeuroNames | 232 |
| NeuroLexID | birnlex_1610 |
| TA98 | A14.1.09.509 |
| TA2 | 5570 |
| FMA | 61839 |
| Anatomical terms of neuroanatomy | |
The GPeGABAergicneurons, allow for its inhibitory function and projectsaxonsto thesubthalamic nucleus(in thediencephalon), thestriatum,internal globus pallidus (GPi) andsubstantia nigra pars reticulata.[1]
The 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 fordeep brain stimulationas a treatment forParkinson's disease.
Function
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Indirect pathway
editThebasal gangliafunctions to tonically inhibit movement, mainly in the absence ofmotor cortexcommand, viaGABAergicinhibition of theventral lateral nucleusandventral anterior nucleusof thethalamus,as well as thesuperior colliculusandmesopontine tegmentumof the brain stem. When movement is required, thecerebral cortexsends commands to thestriatum,which directly inhibits themedial globus pallidusandsubstantia nigra pars reticulata,decreasing thalamus and brainstem inhibition.[1]As the pathway from thestriatumto themedial globus pallidusis monosynaptic (containing onesynapse), it is called thedirect pathway.
Theindirect pathway,which contains the GPe and thesubthalamic nucleus,functions to modulate the effects of the direct pathway. The GPe acts as an inhibitory "control device", adjusting subthalamic nucleus neuronal activity via GABAergic output.[2]
When movement adjustment is required, striatal inhibitoryGABAergicaxons are sent to the GPe, decreasing inhibition of thesubthalamic nucleus.Thesubthalamic nucleus'glutamatergicneurons then stimulate the GPi andsubstantia nigra pars reticulata.
Thismultisynapticindirect striatopallidal pathway allows for regulated excitatory input from the subthalamic nucleus to the GPi andsubstantia nigra pars reticulata.This combines with direct pathway inhibition in the GPi, allowing for fine tuned basal ganglia output, and more controlled movement.
Related pathology
editLateral globus pallidus dysfunction has been observed in the following conditions:
References
edit- ^abParent, 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.PMID7711769.S2CID28252990.
- ^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.PMID7711765.S2CID20808851.
- ^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.ISSN1460-9568.PMC4874844.PMID26841063.
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