1. BASAL NUCLEI
(Basal Ganglia)

2. Basal Nuclei Components
Substantia nigra (within the midbrain)
Subthalamic nuclei (diencephalon)
Corpus striatum
Red nucleus (?)
Claustrum (?)
Nucleus accumbens (?)

3. Corpus Striatum Composed of caudate nucleus + lentiform nucleus:
Striatum = caudate nucleus + putamen.
Pallidum = globus pallidus.
Putamen + globus pallidus = lentiform nucleus.
Controls large subconscious movements of the skeletal muscles.
The globus pallidus regulates muscle tone.

4. Corpus Striatum

5. Substantia Nigra Subdivisions
Dorsal pars compacta:
Has melanin containing neurons and dopaminergic neurons.
Ventral pars reticularis:
Has iron-containing glial cells.
Has serotonin and GABA (no melanin).

6. Substantial Nigra

7. Input Nuclei Striatum Receive widespread input from: Caudate nucleus
Putamen
Nucleus accumbens
Receive widespread input from:
Neocortex
Intralaminar nuclei
Substantia nigra
Dorsal raphe nucleus

8. Input Nuclei Striatum projects to:
Globus pallidus
Substantia nigra
Pars reticularis
Via gabaminergic fibers
Motor and sensory cortices project to putamen.
Association areas of all lobes project to caudate nucleus.

9. Output Nuclei Globus pallidus (medial part) Substantia nigra:
Pars reticularis
Ventral pallidum
Fibers project to:
VA/VL nuclei
Mostly inhibitory

10. General Core Circuit Cerebral cortex to: Striatum to:
Globus pallidus to:
Thalamus to:
Portions of motor cortex to:
Upper motor neurons

11. Basal Ganglia Connections Red = excitatory; Black = Inhibitory
Motor areas of cerebral cortex
Ventrolateral
thalamus
Putamen
Globus pallidus
externus
Output
nuclei
Subthalamic
nuclei
Pedunculo-
Pontine
nuclei
Lateral
Activation
pathways
Reticulospinal and
Vestibulospinal
pathways
Substantia nigra
compacta

12. Thalamic Fasciculi Ansa lenticularis:
Consists of fibers from dorsal portion of globus pallidus.
Loops under internal capsule.
To VA/VL complex.

13. Thalamic Fasciculi Lenticular fasciculus:
Consists of fibers from ventral portion of globus pallidus.
Passes across the internal capsule.
To VA/VL complex.

14. Functions
Basal nuclei set organism’s level of responsiveness to stimuli.
Extrapyramidal disorders are associated with basal nuclei pathology:
Negative symptoms of underresponsiveness:
Akinesias
i.e. Parkinson disease
Positive symptoms of over-responsiveness:
Choreas, athetoses, ballisms
i.e. Huntington’s chorea

15. Dopamine Neuronal System
Consists of nigrostriatal fibers
From pars compacta of substantia nigra
To striatum
Dopaminergic