12 Movement - Basal Ganglia

Question 1

What does the basal ganglia consist of?

Answer 1

Caudate

Puamen

Globus Pallidus

Thalamus

Substantia Nigra

+ ventricles

Question 2

What does the striatum consist of?

Answer 2

The caudate nucleus and putamen

Question 3

What are the 3 feedback loops between the cortex and thalamus? What does each do?

Answer 3

1. Direct Path: via globus pallidus pars interna( GPi)
   
   • increases excitatory thalamocortical feedback by inhibition of GPi. GPi is then unable to send inhibitory signals to Thal.
2. Indirect Path: via GP pars externa (GPe)
   
   • Reduce excitatory thalamocortical feedback by inhibiting GPe. GPE is then unable to send inhibitory signals to GPi. GPi can then send inhibitory signals to Thal.
3. Indirect Path: via subthalamic nucleus (STN)
   
   • Reduce excitatroy thalamocortical feedback
   • Striatum inhibits GPe, which means STN is no longer inhibited. STN sends excitatory feedback to GPi. GPi then sends inhibitory signals to Thal.

Question 4

What are the models of basal ganglia function?

Answer 4

• scaling of movement
• focusing/filtering of movement
• error correction

Question 5

How does the substantia nigra fit in?

Answer 5

Substantia Nigra produces and releases dopamine. Striatum contains two types of dopamine receptors; D1 and D2.

Dopamine is excitatory to D1, inhibitory to D2.
D1 sends inhibitory projections to GPi.
D2 sends inhibitory projects to GPe.