Lecture 12: Basal Ganglia

Question 1

What do the basal ganglia and the cerebellum have in common?

Answer 1

They both do not project directly to the periphery.

Question 2

Basal ganglia lesions often lead to two oppositional symptoms. Name these and give respectively an example of a disease that involves these symptoms.

Answer 2

Hyperkinetic movement disorders: e.g. Huntington’s disease.

Hypokinetic movement disorder: e.g. Parkinson’s disease.

Question 3

Which parts of the basal ganglia constitute that striatum?

Answer 3

The putamen and the caudate nucleus.

Question 4

Which parts of the basal ganglia constitute the nucleus lentiformis?

Answer 4

The putamen and the globus pallidus.

Question 5

Which part of the brain receives all the input to the basal ganglia?

Answer 5

The striatum.

Question 6

Name the main areas of input to the basal ganglia. Are these inputs excitatory or inhibitory in nature?

Answer 6

Cortical (mostly excitatory; glutamate), substantia nigra (excitatory and inhibitory, depending on receptor type; D1, D2; dopamine), intralaminar nuclei of the thalamus (glutamate) and raphe nuclei (serotonine).

Question 7

What is the ‘net result’ in a healthy person, regarding the direct and indirect pathways of the basal ganglia?

Answer 7

The net result is a balance of excitation (direct pathway; facilitating movements) and inhibition (indirect pathway; inhibition of movements).

Question 8

What is the net result in a person with Parkinson’s disease, regarding the direct and indirect pathways of the basal ganglia?

Answer 8

The net result is a disbalance, with decreased excitation (direct pathway; thalamic inhibition is less inhibited) and increased inhibition (indirect pathway; thalamic inhibition is further increased). This results in inhibition of the thalamus, leading inhibited motor activity.

Question 9

What is the net result in a person with Huntington’s disease, regarding the direct and indirect pathways of the basal ganglia?

Answer 9

The net result is a disbalance, with decreased inhibition due to damage of the indirect pathway. This results is excitation of the thalamus, leading to chorea.

Question 10

Describe the direct and indirect pathways projecting from the striatum. Describe the effect of dopamine on the respective pathways.

Answer 10

From striatum to internal segment of globus pallidus or substantia nigra pars compacta. (direct)
Dopamine has an excitatory effect.

From striatum to external segmemt of globus pallidus, then subthalamic nucleus before reaching internal segment of globus pallidus and substantia nigra pars compacta. (indirect)
Dopamine has an inhibitory effect.

Question 11

Name the four channels going through the basal ganglia, including their functions.

Answer 11

Motor channel: general motor control (putamen)
Oculomotor channel: eye movements (caudate nucleus, body)
Prefrontal channel: cognitive functions (caudate nucleus, head)
Limbic channel: emotional functions (nucleus accumbens, ventral caudate, ventral putamen)