Basal ganglia and cerebellar circuits in motor control
The direct and indirect basal ganglia pathways, how dopamine loss gives parkinsonism and striatal loss gives chorea, the subthalamic lesion behind hemiballismus, the logic of deep brain stimulation, and how cerebellar anatomy explains ipsilateral ataxia and the midline versus hemispheric split.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- The basal ganglia choose and scale movements. They act on the motor thalamus by releasing a brake: the output nuclei (GPi and SNr) tonically inhibit the thalamus.
- The direct pathway lifts the brake (more movement). The indirect pathway strengthens it (less movement). Dopamine favours the direct route.
- Too little output gives hyperkinesia (chorea, ballism). Too much gives hypokinesia (parkinsonism).
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Sources
- Principles of Neural Science (6th ed.)McGraw Hill (Kandel, Koester, Mack, Siegelbaum, 2021), 2021
- Localization in Clinical Neurology (8th ed.)Wolters Kluwer (Brazis, Masdeu and Biller), 2022
- DeLong MR, Wichmann T. Circuits and circuit disorders of the basal ganglia. Arch Neurol 2007;64:20-4Archives of Neurology, 2007
- Postuma RB, Lang AE. Hemiballism: revisiting a classic disorder. Lancet Neurol 2003;2:661-8Lancet Neurology, 2003
- Kordower JH, Olanow CW, Dodiya HB, et al. Disease duration and the integrity of the nigrostriatal system in Parkinson's disease. Brain 2013;136:2419-31Brain, 2013
- Last updated
- 14 November 2026
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