Task 2 - Basal Ganglia

Question 1

Input of the Basal Ganglia

Answer 1

The basal ganglia receives input from the cerbral cortex and the substantia nigra and the receiving space in the basal ganglia is the Corpus Striatum

Question 2

Corpus striatum

Answer 2

Part of the basal ganglia, seperated into caudate and putamen

Question 3

From where does output leave the basal ganglia?

Answer 3

Medium spiny neurons converge in the pallidum, which includes the globus pallidus and the substantia nigra pars reticulata), which are the main outputs

Question 4

Corticostriatal pathway

Answer 4

All projections from the cortex to the basal ganglia, specifically the striatum

Question 5

Functional differences between Caudate and Putamen

Answer 5

• Caudate: Receives projections from mutimodal association cortices and from motor areas in frontal lobe that control eye movement
• Putamen: Receives input from the primary and secondary somatosensory cortices, secondary visual cortices, premotor and motor cortices and auditory association areas

Question 6

Direct pathway of the Basal Ganglia

Answer 6

1. Medium spiny neurons send inhibitory signals (GABA) to Globus pallidus internal and the SNPR
2. SNPR send inhibitory signals to Superior colliculus (GABA)
3. The Globus Pallidus internal sends inhibitory signals to VA/VL complex
4. VA/VL complex sends excitatory signals back to cortex

Question 7

Indirect pathway of the Basal Ganglia

Answer 7

1. Medium spiny neurons send inhibitory signals to Globus Pallidus external
2. Globus Pallidus external sends inhibitory signals to internal segment and subthalamic nucleus
3. Subthalamic nucleus sends excitatory signals to internal segment (glutamate) and receives excitatory signals from cortical neurons

Question 8

Center-surround organization of the direct & indirect pathways (a.k.a. focused selection)

Purves

Answer 8

A model which portrays the direct & indirect pathways as functionally organized in a center-surround fashion within the
output nuclei of the basal ganglia

Question 9

Dopaminergic input into the basal ganglia

Answer 9

Striatum projects to SNPC which projects back. The same SNPc neurons can send excitatory inputs to the direct pathway cells and inhibitory input into indirect pathway cells because of different dopamine receptors (D1 and D2)

Question 10

What does D1 do?

Answer 10

• Mediates G-proteins that stimulate cAMP and excites the direct pathway, leading to increased responsiveness to cortical input
• This increases excitability of motor neurons

Question 11

What does D2 do?

Answer 11

• Influences G-proteins that inhibit cAMP, which inhibits the indirect pathway and decreases the responsiveness to cortical input
• This increases excitability of motor neurons

Question 12

Parkinson’s disease

Answer 12

Characterized by tremor at rest, slowness of movement, rigidity of the extremities and neck, minimal face expression; caused by the loss of dopaminergic neurons in the SNPC

Question 13

Huntington’s disease

Answer 13

A hyperkinetic disorder, in which medium spiny neurons that project to the external segment of the globus pallidus degenerate