Lecture 23 + 24 (Basal nuclei)

Question 1

Basal nuclei (BN)

Answer 1

• Regulate cortically initiated motor activity
• Learned movements become automatisms
• Involved memory, emotions and cognitive and linguistic functions

Question 2

Subcortically nuclei - names

Answer 2

1. Striatum: caudate nucleus and putamen
2. Globus pallidus (GP) (externa and interna)
3. Subthalamic nucleus (STN)
4. Substantia nigra (pars compact (SN_pc) and reticulata (SN_pr))

Question 3

Subcortical nuclei - function

Answer 3

• Normal voluntary movement
• No direct input and output to spinal cord
• Input: cortex
• Output: brain stem & via thalamus to prefrontal, premotor and motor cortex

Question 4

BN lesions

Answer 4

• Tremor & other involuntary mvts
• Changes in posture & muscle tone
• Poverty and slowness of mvt without paresis
  Either diminished or excessive mvts
  Also:
• Neuropsychiatric
• Cognitive
• Behavioural

Question 5

Pyramidal vs Extrapyramidal Syndromes

Answer 5

Pyramidal: spasticity & paresis
Extrapyramidal: involuntary mvts, muscle rigidity and immobility without paresis
Although division not correct; very interconnected

Question 6

Basal Nuclei - input

Answer 6

• Major source: cortex; NT glutamate (excitatory)
• Major recipient: striatum
• Also input from SN_pc (dopamine)

Question 7

Basal Nuclei - output

Answer 7

• Output nuclei: GP_i and SN_pr
• Project to thalamus
• GABA-ergic connections, inhibits thalamus so suppresses movement
• Thalamus projects to frontal lobe

Question 8

Striatium

Answer 8

• GP_i and SN_pr tonically inhibit thalamus and brainstem
• 2 parallel pathways to GP_i and SN_pr: direct/indirect and hyperdirect

Question 9

Direct pathway

Answer 9

1. Activate putamen
2. Increase of inhibition of GP_i
3. Decrease of inhibition of thalamus
4. Thalamus output increases
5. Mvt
   Striatal neurons contain D1 receptors (dopamine): activates putamen

Question 10

Indirect pathway

Answer 10

1. Activate putamen
2. Increase inhibition of GP_e
3. Decrease inhibition of STN
4. Increase activity of STN/GP_i
5. Increase inhibition of thalamus
6. Decrease activity of cortex
7. Less mvt
   Striatal neurons contain D2 receptors (dopamine): inhibits putamen

Question 11

Dopamine (DA)

Answer 11

• Facilitates movement
• Input to both pathways lead to same effect
• Reduces inhibition of thalamocortical neurons

Question 12

Movement disorders resulting from imbalances in pathways

Answer 12

Hypokinetic (PD)
- akinesia
- bradykinesia
- rigidity and tremor
Hyperkinetic (HD)
excessive motor activity
- diskinisia
- hypotonia