Basal Ganglia Anatomy and Function

Question 1

Frontal slide through the cerebrum showing both sides of the brain

White grey= grey matter; dark grey= white matter

Question 2

Where are the basal ganglia located?

Answer 2

deep within the cerebrum (or telencephalon), the front most part of the brain

Question 3

What are the basal ganglia?

Answer 3

Caudate

Putamen

Globus pallidus (internal and external)

Question 4

Why is the substantia nigra black?

Answer 4

because it contains nuclei that contain black melanin

Question 5

Close up of the basal ganglia. Where is the caudate nucleus located?

Answer 5

medial and along the lateral ventricles

IC= internal capsule

CC= corpus callosum

Question 6

The basal ganglia are primarily involved in what?

Answer 6

movement control (somatic basal ganglia mostly)

motivation, reward, and affect (limbic basal ganglia)

Question 7

The basal ganglia can be divided into what two categories of structure?

Answer 7

the somatic basal ganglia (dorsal) and the limbic basal ganglia (ventral)

Question 8

What is the limbic basal ganglia composed of?

Answer 8

the nucleus accumbens, olfactory tubercles, and the ventral pallidum

Note that the somatic BG include the caudate, putamen, and globus pallidus

Question 9

Left side view of the basal ganglia.

Note that the internal capsule seperates the caudate nucleus from the putamen in space

Question 10

The tail of the caudate wraps behind and then ventral underneath the putamen to end as what structure?

Answer 10

amygdaloid nucleus

Question 11

Note how the putamen and caudate nucleus are collectively called what?

Answer 11

the striatum

Question 12

Answer 12

Question 13

This image is a brain with a stain showing which nuclei make dopamine. Notice how the substantia nigra is the most dominant dopamine making nuclei

You can also see that the putamen, and the head and tail of the caudate are all brown. Why?

Answer 13

Because the substantia nigra ha axons that travel into the head of the caudate, the putamen, and tail of caudate, and form dopaminergic terminals there (the globus pallidus does not receive many dopamine terminals, so its pale)

Question 14

The _____ ______ is the midbrain continuation of the internal capsule

Answer 14

the cerebral peduncle

Question 15

Note the labels individual dopaminergic neurons of the substantia nigra. Where are they located?

Answer 15

in an upper part of the substantia nigra, called the pars compacta (because they are arranged in a compact layer)

Question 16

The region beow the pars compact is called what?

Answer 16

the pars reticulata (a reticulum is a net-like meshwork of fibers) - note that this area contains few dopaminergic neurons. Rather, its neurons commonly very much resemble those in the globus pallidus in their chemistry, shape and function.

Thus, while the pars compacta and the pars reticulata together make up the substantia nigra, only the pars compacta really contains melanin

Question 17

Question 18

What neuron types make up the striatum?

Answer 18

A (aspiny) neurons and SN (spiny) neurons

In the striatum, 5% are A neurons

Question 19

Describe A neurons

Answer 19

An aspiny neuron has dendrites that do not possess stubby protrusions on them (the stubby protrusions are called spines). About 95% of neurons in the striatum are SN neurons

Question 20

T or F. SN neurons are usually smaller than A neurons

Answer 20

T.

Question 21

Closeup of a SN neuron. Again, A neurons are larger than SN neurons

Neurons that need to integrate info from diverse sources possess dendritic spines

Question 22

One important point about spiny neurons is that they have what?

Answer 22

a long axon that leaves the striatum (by contrast, A neurons have axons that are short and dont leave the striatum)

Because of this, SN neurons in the striatum are called projection neurons, while the A neurons are called the local circuit neurons, or interneurons. Thus, it is spiny neurons that transmit decisions to other brain areas

Question 23

All spiny neurons use what neurotransmitter?

Answer 23

GABA

Question 24

What are the different types of projection (spiny) neurons based on?

Answer 24

-type of neuropeptide contained (neuropeptides are adjunct neurotransmitters that neurons often use, but they also can be neurochemical signatures for defining neuron subtypes)

Question 25

Subtypes of spiny neurons in the striatum

Answer 25

1) One subtype of projection neuron in the striatum, in addition to making GABA, makes the opiod neuropeptide enkephalin (ENK). 2) The second subtype makes the neuropeptide substance P (these neurons project to the GPi)

Question 26

The characteristics of the ENK neurons in the striatum is that they nearly all project where?

Answer 26

the GPe

Question 27

Answer 27

Question 28

Where are substance P and ENK found in the substantia nigra?

Answer 28

Substance P terminals are located in the upper shelf of the SN where dopaminergic neurons are located (the pars compacta, aka SNc) and in the region of the SN below the dopaminergic neurons (the pars reticulata, aka SNr). **Thus, substance P neurons in the striatum include neurons projecting to the GPi, SNc, and SNR** By contrast, the ENK neurons in the striatum have only a hint of a projection to the substantia nigra, and that is only to the very most medial aprt of the SN

Question 29

One important thing to know about substance P and ENK neurons **in the striatum is that they are intermingled**

Question 30

In addition to containing substance P, these neurons also \_\_\_\_\_\_\_

Answer 30

a second neuropeptide, an opiod **dynorphin**

Question 31

Notice how all striatal projection neurons possess a certain type of dopamine receptor. Those projecting to the GPe (ENK neurons) bind to what receptor?

Answer 31

D2

Question 32

Notice how all striatal projection neurons possess a certain type of dopamine receptor. Those projecting to the GPi, SNr, and SNc (Substance P/Dynorphin neurons) bind to what receptor?

Answer 32

D1 receptors NOTE: Remember that D1 and D2 receptors function differently

Question 33

What do striato-GPe neurons (ENK) do?

Answer 33

inhibit conflicting movement with desired movement

Question 34

What do striato-GPi neurons (SP/DYN) do?

Answer 34

promote/initiate limb movement

Question 35

What do striato-Snr neurons (SP/DYN) do?

Answer 35

promote eye movement

Question 36

What do striato-SNc neurons (SP/DYN) do?

Answer 36

regulate dopamine neurons

Question 37

There are four types of interneurons in the striatum, distinguished by their neurochemistry, by the size of their cell body, and by which neuron in the striatum they project, and which parts of the brain they receive input from. What are they?

Answer 37

cholinergic paravalbuminergic somatostatinergic calretinergic

Question 38

Note that each interneuron type makes up about 1% of neurons in the striatum and together they make up about 5%

Question 39

One important interneuron type in the striatum that hsa eben the target of therapies directed at basal ganglia disease is the \_\_\_\_\_\_

Answer 39

cholinergic- this interneuron has a big cell body

Question 40

Colinergic interneurons in the striatum use what neurotransmitter?

Answer 40

ACh

Question 41

Parvalbuminergic interneurons contian calcium binding protein and use what transmitter?

Answer 41

GABA (the neurons are larger than projection neurons, but smaller than the large cholinergic interneurons)

Question 42

The somatostatinergic interneurons, containing somatostatin (a neuropeptide), uses what transmitter?

Answer 42

GABA (these neurons have cell bodies the same size as spiny neurons)

Question 43

Calretinergic interneurons also use GABA as their neurotransmitter and contain \_\_\_\_\_

Answer 43

calretinin, a calcium binding protein

Question 44

Which interneurons are impervious to Huntington disease?

Answer 44

somatostatin interneurons

Question 45

Somatostatin interneurons also produce \_\_\_\_\_

Answer 45

Neuropeptide Y (NPY)

Question 46

Answer 46

Note that as Huntington progresses, spiny neurons die. By grade 3, 60% of SNs are lost, and the striatum, GPe, and GPi are greatly shrunken as a result. Nonetheless, somatostatin neuron abundance is preserved in grade 3 and 4.

Question 47

Question 48

Note that ____ and ______ interneurons also survive well in Huntington disease

Answer 48

**Cholinergic and calretinergic interneurons**; but Parvalbuminergic interneurons do not survive well

Question 49

What is the main function of cholinergic interneurons?

Answer 49

modulate PNs- opposes DA action

Question 50

What is the main function of parvalbuminergic interneurons?

Answer 50

inhibit PNs- sharpen activity role of somatostatinergic and calretinergic interneurons unknown

Question 51

Question 52

What is the major neuron type with the globus pallidus?

Answer 52

large A neurons, with long dendritic trees arranged in teh vertical axis of the GPe and GPi. Many striatal neurons send their terminal onto the dendrities of any given globus pallidus neuron and they integrate info from the many striatal neurons that project to it.

Question 53

Both GPe and GPi neurons are \_\_\_\_-ergic and they send their axons out of the globus pallidus to their target area

Answer 53

GABA

Question 54

Where does the GPe project to?

Answer 54

the subthalamic nucleus

Question 55

Where does the GPi project to?

Answer 55

the motor thalamus

Question 56

There are two nuclei making up the motor thalamus, namely:

Answer 56

the ventral anterior nucleus (VA) ventral lateral nucleus (VL) (two parts- the C (caudalis) and O (oralis) parts)

Question 57

Answer 57

Question 58

The ______ \_\_\_ ______ \_\_\_\_\_ also projects to the motor thalamus

Answer 58

substantia nigra pars reticulata

Question 59

Cortical projection targets of the motor thalamus. Where does the VA project to? VL?

Answer 59

VA: area 6, which is pre-motor cortex VL: area 4, which is motor cortex Note that this illustration makes the point that the basal ganglia send much of its output to motor-related cortex

Question 60

What are the major inputs into the striatum?

Answer 60

the cortex the thalamus dopaminergic input from the substantia nigra pars compacta

Question 61

What is the CM of the thalamus?

Answer 61

the centre median, part of the intralaminer thalamus (note that the intralaminar thalamus is the source of one of the major inouts to the striatum, but it is not currently well defined)

Question 62

The major input to straitum that is clearly central to the function of the basal ganglia is what?

Answer 62

input from the cerebral cortex- almost all of the cerebral cortex projects to the striatum

Question 63

The cortical neurons that project to the striatum are what?

Answer 63

layer 5 pyramidal neurons. Many of the neurons in layer 5 that project to the striatum also send motor commands to the spinal cord and pre-motor neurons of teh hindbrain

Question 64

Note that dopaminergic terminals (from the pars compacta of the SN) for input into the basal ganglia are located where?

Answer 64

in the caudate and putamen, not the GPe or GPi

Question 65

How does the cortical input transmit to the basal ganglia?

Answer 65

the cerebral cortex input ends on the tips of the spines of the spiny neurons, using glutamate as its neurotransmiiter.

Question 66

How does the SN dopaminergic input transmit to the basal ganglia?

Answer 66

it ends on the sides of the spines of spiny neurons (this the dopaminergic input can modulate the corticla input to the spine ends)

Question 67

Interplay of the striatal input to the globus pallidus and the subthalamic nucleus input. Explain

Answer 67

WHile the GPe projects to the subthalamic nucleus, the subthalamic nucleus mainly projects back to the GPi, by wrapping around the smooth dendrities of the GPi neurons, which also receive terminals from striatal substance P containing neurons

Question 68

Question 69

Answer 69

Question 70

Answer 70