1. Basal Ganglia
Dr. G.R. Leichnetz

2. Basal Ganglia
The group of subcortical nuclei collectively known as the “basal ganglia” are involved in orchestrating automated patterns of movement, such as walking, driving a car, riding a bicycle.
The term includes: caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra.

3. The basal ganglia include: Caudate Putamen Globus pallidus
Caudate nucleus
The basal ganglia include:
Caudate Putamen
Globus pallidus
Subthalamic nucleus
Substantia nigra
Striatum
Subthalamic nucleus
Putamen
Globus pallidus
Burt
Substantia nigra

4. Striatum: caudate + putamen Lentiform nucleus: putamen + globus pallidus
Caudate Nucleus
Putamen
Caudate
Putamen
Globus Pallidus
Globus Pallidus

5. (which is involved in the planning and programming of movements).
Supplementary Motor Cortex
These structures have extensive interconnections, but ultimately their major output flows from the internal segment of the globus pallidus to the motor thalamus (VA/VL), and then is conveyed to the supplementary motor cortex (M-II)
(which is involved in the planning and programming of movements).
Motor thalamus
Globus pallidus, GPi
Subthalamic nucleus
Striatum
Substantia nigra
From Kandel, et al.

6. Striatum

7. Striatum: Caudate and Putamen
Caudate Nucleus
Putamen
Putamen GP
Globus Pallidus
In a Nissl-stained section the caudate and putamen are seen as histologically the same structure, separated by the anterior limb of the internal capsule.

8. The striatum consists of two populations of neurons:
Spiny neurons
are the principal cell type, are GABA-ergic, and give rise to all striatal efferents (striatopallidals & striatonigrals).
Aspiny neurons
are cholinergic, short-axon neurons which have intrinsic striatal circuitry (short axons which do not leave the striatum).
From Parent, Carpenter’s Human Neuroanatomy

9. Striatum: Caudate and Putamen
The striatum is organized into subsectors, the striosomes and matrix, that have differential connections.
Caudate Nucleus
Striosomes
Matrix
Putamen
Haines, Fundamental Neuroscience
D1 Dopaminergic receptors predominate in the striosomes; D2 receptors in the matrix
From Parent, Carpenter’s Human Neuroanatomy

10. Corticostriates (glutamatergic, excitatory)
Striatal Afferents
Cortex
There are three principal sources of afferents to the striatum (green):
Corticostriates (glutamatergic, excitatory)
Thalamostriates (glutamatergic, excitatory)
Nigrostriates (dopaminergic)
CM/Pf
Intralaminar complex, thalamus
Substantia nigra
From Haines, Fundamental Neuroscience

11. Corticostriates
Prefrontal Cortex
Corticostriates originate from broad areas of frontal and parietal cortex.
Those from association cortex (prefrontal & parietal) go to the caudate nucleus.
Those from the sensorimotor cortex (pre- and post-central gyri) go to the putamen.
Striatum

12. Thalamostriates originate from the centromedian (CM) and parafascicular (Pf) nuclei of the intralaminar complex of the thalamus CM projects to the putamen Pf projects to the caudate nucleus.
Pulvinar
Pineal
Intralaminar Complex CM
VPL Pf
VPM
Modified from Kandel

13. Nigrostriates
Nigrostriate projections originate from the pars compacta of the substantia nigra.
They are dopaminergic. SN
Pars reticulata SNr
Pars compacta SNc DA

14. Striatal Efferents
The principal efferents of the striatum (red) are:
Striatopallidals “striosomes” to internal segment of the globus pallidus (GPi) & “matrix” to external segment (GPe)
Striatonigrals “striosomes” to pars compacta (SNc) & “matrix” to pars reticulata (SNr) of substantia nigra
All of the efferents of the caudate and putamen are GABA-ergic (inhibitory).
From Haines, Fundamental Neuroscience

15. The direct pathway facilitates movement, while the indirect pathway inhibits movement.
D1 receptors predominate in striosomes (patches) and project directly to the GPi (direct pathway).
D2 receptors predominate in the matrix and project to the GPe (indirect pathway).

16. Huntington’s Chorea is an inherited disease with onset in middle age.
Atrophy of the striatum
Choreiform (dance-like) movements, rigidity (hyperkinetic movement disorder)
Post-mortem coronal section of the brain of a patient with Huntington’s disease. Note atrophy of caudate and putamen and enlarged lateral ventricles.

17. Globus Pallidus

18. C
Globus Pallidus
The globus pallidus has two segments: external and internal P GP
External segment (GPe)
Internal segment (GPi) GP

19. Pallidal Afferents Striatopallidals
The principal source of afferents to the globus pallidus is GABA-ergic striatopallidal fibers from caudate and putamen, which project to both external and internal segments.
Striatopallidals to external segment affect the “indirect loop.”
GPe
GPi
Striatopallidals to the internal segment affect the “direct” loop.
Modified Burt, Textbook of Neuroanatomy

20. Pallidal Efferents: Pallidothalamics & Pallidosubthalamics
All of the efferents of the globus pallidus are GABA-ergic (inhibitory). The external segment projects to the subthalamic nucleus (“indirect loop”; in green) and the internal segment projects directly (“direct loop”) to the motor thalamus (primarily VA) and to intralaminar complex (CM/Pf). VA
Indirect Loop
CM/Pf
GPe
STN
GPi
Modified Burt, Textbook of Neuroanatomy

21. Modified from Kandel
The direct pathway facilitates movement, while the indirect pathway inhibits movement.
D1 receptors predominate in striosomes (patches) and project directly to the GPi (direct pathway).
D2 receptors predominate in the matrix and project to the GPe (indirect pathway).

22. Efferents of the globus pallidus primarily target the motor thalamus (pallidothalamics to VA). Some traverse the internal capsule (fasciculus lenticularis) and some loop around internal capsule (ansa lenticulus); join to form thalamic fasciculus.
Pallidothalamics follow two different routes to the motor thalamus (VA) VA
CM/Pf
Thalamic fasciculus
Fasciculus lenticularis
STN
Ansa lenticularis
Pallidal Efferents

23. Subthalamic Nucleus

24. Subthalamic Nucleus The subthalamic nucleus is part of the subthalamus.
Prerubral Fields H ZI H2
STN

25. Subthalamic Afferents
The subthalamic nucleus receives its principal input from the external segment of the globus pallidus (GPe), and projects to the internal segment of the globus pallidus (GPi); the “indirect loop.” VA
CM/Pf
GPe
STN

26. Modified from: Kandel
Subthalamic nucleus

27. A lesion of the subthalamic nucleus results in contralateral hemiballism.
Ballism- violent, large amplitude, proximal limb movements result from a lesion of the subthalamic nucleus.
Huntington’s disease and hemiballism are hyperkinetic disorders (excessive motor activity)

28. Substantia Nigra

29. SN Substantia Nigra The substantia nigra has two parts:
pars compacta (DA) and the pars reticulata (GABA). SN
Pars reticulata
Pars compacta

30. Substantia Nigra Afferents
Substantia Nigra Afferents Striatonigrals: from caudate & putamen, GABA-ergic
Striosomes- to pars compacta, SN (SNc) Matrix- to pars reticulata, SN (SNr)
Caudate
Putamen
SNr
SNc
From Haines, Fundamental Neuroscience

31. Nigrostriatals (DA)- from SNc to caudate and putamen
Nigral Efferents:
Nigrostriatals (DA)- from SNc to caudate and putamen
Nigrothalamics- from SNr to motor thalamus (VA/VL) (GABA-ergic)
Nigrotectals- from SNr to superior colliculus (GABA-ergic)
Modified from Haines, Fundamental Neuroscience

32. Substantia nigra: pars compacta (DA) to striatum, and pars reticulata (GABA)- to thalamus & superior colliculus
VA & CM/Pf SC
Striatum
Nigrothalamics & nigrotectals GABA
SNr
SNc
Nigrostriates DA

33. The nigrostriatal projection from the pars compacta of the SN to the caudate and putamen is dopaminergic.
Loss of dopaminergic neurons in the SNpc is associated with Parkinson’s disease.
L-dopa therapy is recommended to replace depleted DA (crosses blood brain barrier)
Post-mortem section of the midbrain from a patient with Parkinson’s disease shows loss of neuromelanin in the SN

34. Parkinson’s Disease Resting tremor Bradykinesia
Festinating Gait- baby steps
“Freezing”(inertia) difficulty initiating movements
Rigidity
Masked face
Parkinson’s disease is a hypokinetic disorder (deficient motor activity)

35. Basal Ganglia Loop With Ipsilateral Cortex

36. The basal ganglia are in a neural loop with the ipsilateral motor cortex.
Corticostriate projections originate from broad areas of the frontal and parietal cortex,
but thalamocortical projections from VA, carrying the influence of basal ganglia, project more narrowly to the supplemental motor area (M2 premotor cortex) involved with the planning and programming of movements.
From Kandel, et al.

37. Motor cortex
Therefore, if lesioned, the dysfunction affects the ipsilateral motor cortex, and deficits (thru the pyramidal system) are expressed on the contralateral side of the body.
The basal ganglia are connected in a loop with the ipsilateral motor cortex
From: Niewenhuys, The Human Nervous System