功能性神經解剖學 Chapter 19. Basal Ganglia 林 永 煬 國立陽明大學 腦科學研究所

1. 功能性神經解剖學 Chapter 19. Basal Ganglia 林 永 煬 國立陽明大學 腦科學研究所

2. “An Essay on the Shaking Palsy” by James Parkinson (1817) Extrapyramidal vs. Pyramidal disorders

4. Basal ganglia and surrounding structures, as seen in an axial section

5. Basal ganglia and surrounding structures, as seen in coronal sections

6. Terminology associated with the basal ganglia

7. Parasagittal section showing how the striatum got its name

8. Striopallidal fibers: from putamen to globuspallidus (pallidum) Corticostriate fibers: from cerebral cortex to putamen, caudate nucleus, or nucleus accumbens Pallidothalamic fibers: from globuspallidus to thalamus Nigrostriatal fibers: from substantianigra to striatum Nigroreticular fibers: from substantianigra to reticular formation Thalamostriate fibers: from intralaminar nuclei to striatum

9. Three-dimensional reconstruction of the striatum and globuspallidus inside a translucent CNS

10. The compact (SNc) and reticular (SNr) parts of the substantianigra

11. Basal ganglia circuitry Corticostriate inputs: Afferents from cortex to striatum and subthalamic nucleus Excitatory (glutamate) connections Output projections: Efferents leaving from globuspallidus (GPi) and substantianigra (SNr) to thalamus Inhibitory (r-aminobutyric acid [GABA]) connections Thalamocortical projections: Excitatory (glutamate) connections

12. Principal inputs to and outputs from the basal ganglia

13. Cortical functions related to basal ganglia circuitry Movement Cognition Emotion Motivation

14. Parallel loops through the basal ganglia

15. Cortical functions related to basal ganglia circuitry Motor functions: sensorimotor cortex  putamen  GP  thalamus  motor/premotor/supplementary motor areas Cognitive functions: association cortex  caudate nucleus  GPi-SNr  thalamus  prefrontal areas Emotion/motivation: amygdala/hippocampus/limbic cortex  ventral striatum (nucleus accumbens)  ventral pallidum  thalamus (dorsomedial nucleus)  temporal/ hippocampus/limbic cortex

16. Major connections of the striatum

17. Medial (A) and lateral (B) views of the left striatum showing the somatotopic representation of body parts

18. Chemical compartmentalization of the striatum * * CN IC P A P=putamen, CN=caudate nucleus, IC=internal capsule, A=nucleus accumbens Acetylcholinesterase (AChE)-rich background (matrix) with embedded AChE-poor regions (striosomes*) Caudate nucleus stained for enkephalin Caudate nucleus stained for AChE High enkephalin levels are found in the peripheries of striosomes.

19. Case presentation A 25-year-old woman with dramatic change in cognition, motivation, and self-care.

20. Contrast-enhanced computed tomography scans of a 25-year-old woman with dramatic change in cognition, motivation, and self-care. Acute stage 8 months later

21. Major connections of the external segment of the globuspallidus (GPe)

22. Afferents to GPiand SNr Efferents from GPiand SNr GPi and SNr receive inhibitory inputs from striatum, and excitatory inputs from STN. GPi and SNr provide output from basal ganglia.

23. Subthalamic fasciculus interconnecting STN and GPi

24. Major connections of STN STN provides a powerful excitatory input to GPi and SNr. Major inputs to STN arise not only from GP but also from cerebral cortex. Different sectors of STN deal with motor, cognitive, affective functions.

25. Abnormalities of movement due to basal ganglia disorders Hyperkinetic disorders: tremor, chorea, athetosis, ballismus, hemiballismus Disturbance of muscle tone: dystonia Huntington’s disease Parkinson’s disease

26. Hemiballismus Video show s/s: wild flailing movements of one arm and leg Lesion location in contralateral STN Most often seen in older people with a stroke involving a ganglionic branch of posterior cerebral artery

27. Contrast-enhanced mass in left STN of a 65 y/o male HIV-positive patient with unintentional, forceful flinging movements of right limbs. Longitudinal slice of a normal brain

28. Huntington’s disease s/s: involuntary choreiform movements, alterations of mood or cognitive function dementia and personality change Symptom onset at age of 30 – 50 years Inherited in an autosomal dominant pattern, with a defective gene at short arm of chromosome 4 Pathomechanism: striatal (esp. caudate nucleus) and cortical degeneration Video show

29. MRI scan in a 29 y/o man with Huntington's disease MRI scan in a normal individual Dorsal-ventral degeneration gradient (red > blue)

30. Parkinson’s disease s/s: tremor rigidity (increased muscle tone) slow movements (bradykinesia, hypokinesia) stooped posture Pathomechanism: degeneration of substantianigra (esp. SNc, pigmented nigral cells)

31. The midbrain of a patient with Parkinson's disease, showing loss of pigmentation in the compact part of the substantianigra (*)

32. A model for movement control by basal ganglia (through excitatory (green) and inhibitory (red) interactions) Indirect pathway Direct pathway Loss of dopamine neurons from SNc causes a reduced thalamic and cortical output. (e.g. PD) Loss of excitatory STN projections (e.g. hemiballismus) Dopamine excites direct pathway, but inhibits indirect pathway.

33. Increased blood flow in the supplementary motor area (S) and premotor cortex (P) of Parkinson's disease patients during movement following treatment with levo-dopa

34. Improvement in motor system function of Parkinson's disease patients following unilateral pallidotomy