Basal Ganglia

Question 1

What is the purpose of the basal ganglia

Answer 1

Action selection: selecting and promoting one action while suppressing competing actions

Question 2

Name 3 neuropsychiatric disorders related to problems with the basal ganglia

Answer 2

OCD, ADHD, Tourette syndrome

Question 3

What is the “default” setting of the basal ganglia

Answer 3

To suppress movement

Question 4

How are habits formed

Answer 4

There is a repeated selection of actions with positive outcomes, which leads to these actions being chunked/hardwired together

Question 5

What results from the ability to group chunks together

Answer 5

Complex behaviors, which allows for multitasking

Question 6

Is it easy or difficult to interrupt actions that are chunked together?

Answer 6

Difficult

Question 7

What is operational learning?

Answer 7

Unconscious process by which we associate our chunked actions with their immediate consequences; this biases our actions toward ones associated with reward and away from those associated with negative consequences

Question 8

Which is greater in the basal ganglia, number of inputs or number of outputs?

Answer 8

inputs

Question 9

What type of neurons maintain the default state of the basal ganglia?

Answer 9

Tonic GABA-ergic, inhibitory neurons

Question 10

What makes up 90% of the striatal neurons?

Answer 10

Medium, spiny neurons; GABAergic, spine-covered dendrites

Question 11

What is efference copy?

Answer 11

Bias toward current actions, behavioral continuity

Question 12

What are the 4 major components of the basal ganglia

Answer 12

1. Striatum = caudate + putamen (dorsally) + nucleus accumbens (ventrally)
2. Globus pallidus = lateral + medial GP, found ventral to putamen
3. Substantia Nigra = Pars reticulata + pars compacta (dopaminergic)
4. Subthalamic nucleus

Question 13

What is the dorsal dopaminergic projection of the basal ganglia?

Answer 13

Substantia nigra pars compacta (cell body) –> caudate + putamen

Question 14

Does movement result from the dorsal or ventral dopaminergic projection of the basal ganglia?

Answer 14

Dorsal

Question 15

What is the ventral dopaminergic projection of the basal ganglia?

Answer 15

Ventral tegmental area (cell body) –> nucleus accumbens

Question 16

Do reward-driven behaviors result from dorsal or ventral dopaminergic projections of the basal ganglia?

Answer 16

Ventral

Question 17

What type of movements is dopamine required for?

Answer 17

Goal-directed movements

Question 18

What is the function of the hyperdirect pathway

Answer 18

To stop current movement immediately

Question 19

What is the function of the direct pathway

Answer 19

To release a selected movement from suppression

Question 20

What is the indirect pathway

Answer 20

It has mixed effects, but the most dominant is to suppress competing, non-selected movements

Question 21

What is the hyper direct pathway, starting from stimulation of myelinated fibers of the motor cortex

Answer 21

Glutamate release by motor cortex neurons onto subthalamic neurons, resulting in glutamate release on the internal globus pallidus, causing inhibition by the GABAergic neuron onto the VL/VA thalamus so that it cannot release glutamate onto the motor cortex to continue the loop

Question 22

What is the prevalence of Parkinson’s disease

Answer 22

1% of the U.S. population over the age of 50

Question 23

What is the etiology of Parkinson’s Disease

Answer 23

Degeneration of substantia nigra PARS COMPACTA (dopaminergic region)

Question 24

What are the 3 symptoms commonly associated with Parkinson’s disease

Answer 24

Akinesia, resting tremor, rigidity

Question 25

Which of the 3 skeletomotor loop pathways is affected in Parkinson's Disease

Answer 25

Direct, resulting in little to no movement

Question 26

What are the 3 treatment options for PD?

Answer 26

L-Dopa (DA precursor) Pallidotomy (medial globus pallidus) Subthalamic nucleus deep brain stimulation

Question 27

What is the prevalence of Huntington's Disease?

Answer 27

4-5/million in the U.S., adult onset

Question 28

What is the etiology of Huntington's disease

Answer 28

CAG repeat mutation on chromosome 4, resulting in degeneration of striatal neurons (starting with the caudate)

Question 29

Which pathway is first affected in Huntington's disease

Answer 29

Indirect (D2 --> lateral globus pallidus), resulting in excessive movement

Question 30

What are the 2 main symptoms associated with Huntington's Disease

Answer 30

Initial hyperkinesia, chlorea

Question 31

Why is there initial hyperkinesia

Answer 31

Striatal neuron projection to the external globus pallidus dies, affecting the indirect pathway

Question 32

What is chlorea

Answer 32

Quick, jerky, dancing movements of the extremities, symptomatic of HD

Question 33

What is the treatment for Huntington's disease

Answer 33

No cure, focus therapy on treating symptoms

Question 34

Which group of people is Hemiballism most prevalent in?

Answer 34

Individuals with East Asian origin

Question 35

What are the symptoms of Hemiballism

Answer 35

Violent "throwing" movements of one of the arms or legs

Question 36

What is the etiology of hemiballism

Answer 36

Damage to the contralateral subthalamic nucleus

Question 37

Which pathways is affected in hemiballism

Answer 37

Indirect at the glutamatergic neuron of the subthalamic nucleus

Question 38

What are the 3 most common causes of hemiballism

Answer 38

Focal stroke, hyperglycemia (secondary to diabetes), and toxoplasmosis lesions in individuals with HIV

Question 39

What are the treatments for hemiballism

Answer 39

They are aimed at the cause of the lesion; dopamine receptor ANTagonists

Question 40

What is the striatal component of the dorsal extra-pyramidal system?

Answer 40

Caudate and putamen

Question 41

What is the pallidal component of the dorsal extra-pyramidal system?

Answer 41

Globus pallidus, substantia nigra, pars reticulata

Question 42

What is the dopaminergic innervation of the dorsal extra-pyramidal system?

Answer 42

Substantia nigra, pars compacta

Question 43

What is the cortical input of the dorsal extra-pyramidal system?

Answer 43

Neocortex

Question 44

What is the thalamic target of the dorsal extra-pyramidal system?

Answer 44

Ventral lateral and ventral anterior (VL/VA thalamus)

Question 45

What is the striatal component of the ventral limbic striatal system

Answer 45

Nucleus accumbens, olfactory tubercle

Question 46

What is the pallidal component of the ventral limbic striatal system

Answer 46

Ventral pallidum

Question 47

What is the dopaminergic innervation of the ventral limbic striatal system

Answer 47

Ventral tegmental area (VTA)

Question 48

What is the cortical input of the ventral limbic striatal system

Answer 48

Limbic cortex

Question 49

What is the thalamic target of the ventral limbic striatal system

Answer 49

Mediodorsal

Question 50

What are the 2 main components of the ventral striatum?

Answer 50

Nucleus accumbens (ventral to caudate) and olfactory tubercle

Question 51

What is the function of the ventral striatum?

Answer 51

Motivation to action, expression of motivated behaviors

Question 52

Describe the location of the ventral pallidum

Answer 52

Ventral to the globus pallidus and anterior commisure

Question 53

What are the components of the ventral pallidum

Answer 53

Nucleus basalis of Meynert (cholinergic), nucleus of diagonal band, septal nuclei

Question 54

What is the function of the ventral pallidum?

Answer 54

To regulate eye-head movements for attention, visceral autonomic responses (emotion), and it is implicated in induction and expression of motivated behaviors like addiction

Question 55

What is the prevalence of schizophrenia in the U.S.

Answer 55

1% of the population

Question 56

What is the etiology of schizophrenia

Answer 56

Excessive dopamine in the ventral striatum and dysregulation of prefrontal cortex glutamate

Question 57

Which receptor do anti-psychotics bind most strongly to?

Answer 57

D2 receptors, which are highly expressed in the nucleus accumbens

Question 58

Which loop is affected in OCD?

Answer 58

Indirect