Anatomy Basal Ganglia

Question 1

What are basal nuclei

Answer 1

Large clumps of nuclei that function the same

Get the majority of their afferent signals from the cerebral cortex

Question 2

What higher CNS system does the basal nuclei inhibit?

Answer 2

The thalamus.

Work to regulate the thalamus excitation to the cerebral cortex

Question 3

What components make up the basal nuclei?

Answer 3

Sub thalamic nuclei

Substantial Nigra

Putamen

Caudate nucleus

Amygdala (sometimes)

Nucleus accumbens

Substantia Innominata

Question 4

Neostritaum

Answer 4

A basal ganglia that composes the caudate nucleus and the putamen
- receives all input into the basal nuclei

Question 5

Ventral striatum (nucleus accumbens)

Answer 5

Includes

• nucleus accumbens
• head of the caudate nucleus
• olfactory tubercle

Primary function is in connecting limbic circuitry

Question 6

Striosomes

Answer 6

Patches within the caudate nucleus and putamen (most dense in the head of the caudate)

Are acetylcholinesterase poor

Contain large amounts of one or more neuropeptides and opiate receptors

Receive input from the limbic regions and send projections to the substantia Nigra

Question 7

Matrix of the putamen and caudate

Answer 7

Areas that surround the striosomes

Acetylcholinesterase rich

Receive inputs from sensory and motor cortex and project to the globus pallidus

Question 8

Pallidus complex of the basal ganglia

Answer 8

Composed of:

• globus pallidus
• ventral pallidus
• contains primary GABAergic neurons with high rate of activity
• in Alzheimer’s, ventral pallidus cells collectively called the nucleus of meynert are destroyed

Question 9

What parts make up the striata complex?

Answer 9

Neostriatum

Ventral striatum

Question 10

Sub thalamic nucleus

Answer 10

Lens shaped cell group that use excitatory signals (glutamate)

• Are usually inhibited by the globus pallidus constantly, however in Parkinson’s disease, this inhibition is negated.
• results in spastic, uncontrolled motor defects

Question 11

Nigra complex

Answer 11

Composed of the substantia Nigra and the ventral tegmental area

Substantia Nigra:

• pars compacts = project dopamine to the caudate nucleus and putamen
• pars reticulate = project GABA to the superior colliculus, thalamus and pons
• in Parkinson’s, the pars compacta cells are destroyed

Ventral tegmental area:

• medial to the substantia Nigra
• releases dopamine to the amygdala and limbic system
• plays an important role in the reward/motivation complex as well as addiction

Question 12

Anterior choroidal artery

Answer 12

Comes off the internal carotid at the level of the optic chiasm

Supplies:

• hippocampus
• internal capsule
• globus pallidus
• lateral portions of the thalamus

Question 13

Medial striate artery (recurrent artery of heubner)

Answer 13

Arises from the anterior cerebral artery at the level of the optic chiasm

Supplies:

• internal capsule
• putamen
• septal nuclei
• anteriomedial part of th head of the caudate nucleus

Question 14

Lenticulostriate arteries

Answer 14

Branches off the middle cerebral artery

Supply:

• putamen
• caudate nucleus
• anterior limb of the internal capsule

Question 15

How does all input get to th basal nuclei?

Answer 15

Via the striatum (caudate nucleus and putamen)

Question 16

Areas of the cerebral cortex that project afferents to the putamen

Answer 16

Primary motor

Secondary motor

Primary somatosensory

Question 17

Areas of the cerebral cortex that project to the caudate

Answer 17

Cortical association areas

Frontal eye fields

Limbic regions

Question 18

How does the thalamus and substantia Nigra provide afferent fibers to the striatum?

Answer 18

Thalamostriate and nigrostriatal fibers respectively

Question 19

Direct pathway of the intrinsic basal nuclear connections

Answer 19

Facilitates flow of information through the thalamus to the internal globus pallidus by releasing the thalamus from its pallidus inhibition

Goes cortex -> putamen -> internal globus pallidus -> thalamus

Question 20

Indirect pathway intrinsic basal nuclear connections

Answer 20

Inhibits flow to the globus pallidus directly via releasing the sub thalamic nucleus from inhibition
- goes cortex -> putamen -> external globus pallidus -> subthalamic nuclei -> internal globus pallidus -> thalamus

Question 21

Globus pallidus Outputs from the basal nuclei

Answer 21

Arise form the internal segment of the globus pallidus

Uses two bundles of fibers:

• ansa
• lenticular fasciculus (H2 field)
• both join at the prerubral field (H field) and turn into the thalamic fasciculus (H1 field)

Thalamic fasciculus projects to the VL/VA nuclei of the thalamus and then to the entire frontal lobe

Question 22

Substantia Nigra outputs from the basal nuclei

Answer 22

Arise from pars reticulata

2 pathways

• VA/VL nuclei of the thalamus -> motor areas of the cerebral cortex
• superior colliculus -> tectospinal pathway

Question 23

What are the 4 parallel circuits (functional loops) of the basal ganglia?

Answer 23

Motor channel (loop)

Prefrontal channel (executive loop)

Oculomotor channel (visuomotor loop)

Limbic channel (motivational loop) 
* ventral striatum pathway 

*dorsal striatum pathway is motor, prefrontal and Oculomotor channels combined

Question 24

Motor loop

Answer 24

Initiation and control of motor responses

Promotor cortex and supplementary motor cortex -> putamen -> ventral globus pallodus and dorsal substantia Nigra -> VL/VA thalamus -> back to cortex

Question 25

Prefrontal loop

Answer 25

Cognitive functions and executive planning functions

Dorsolateral prefrotnal cortex -> head of the caudate nucleus -> dorsal globus pallidus and rostral substantia Nigra -> VA/MD thalamic nuclei -> back to cortex

Question 26

Limbic channel

Answer 26

Involved in emotions and motivational drives, also psychiatric disorders

Orbital medial and prefrontal cortex -> ventral striatum -> ventral pallidus and rostral substantia Nigra -> mediodorsal (MD) thalamic nucleus -> back to cortex

Question 27

Oculomotor loop

Answer 27

Modulates visual functions and eye movements

Frontal lobe and eye fields -> body of the caudate nucleus -> dorsal pallidus and ventral substantia Nigra -> VA/MD thalamic nuclei