Lecture 14

Question 1

What are the three layers of the cerebellar cortex?

Answer 1

1. Molecular layer (outer): dendrites, parallel fibres
2. Purkinje cell layer (middle): Purkinje cell bodies
3. Granular layer (inner): granule cell bodies

Question 2

What is the primary output neuron of the cerebellar cortex?

Answer 2

Purkinje cells – Project to deep cerebellar and vestibular nuclei.

Question 3

What are the two main excitatory inputs to Purkinje cells?

Answer 3

• Parallel fibres from granule cells; carry general sensory/motor input
• Climbing fibres from the inferior olive; carry error signals that modulate synaptic plasticity and cerebellar output

Question 4

What is the difference between simple and complex spikes in Purkinje cells?

Answer 4

• Simple spikes: Triggered by parallel fibres; general output
• Complex spikes: Triggered by climbing fibres; burst-like error signal

Question 5

What are the deep cerebellar nuclei and their positions?

Answer 5

• Dentate (lateral)
• Interposed (Emboliform + Globose)
• Fastigial (medial)

Question 6

What are common symptoms of cerebellar dysfunction?

Answer 6

• Ataxia (lack of coordination)
• Tremor
• Dysmetria (overshoot/undershoot)
• Dysdiadochokinesia (impaired rapid alternating movements)

Question 7

What is cerebellar cognitive affective syndrome?

Answer 7

A condition involving deficits in executive function, language, affect, and social behaviour due to cerebellar damage.

Question 8

What is cerebellar hypoplasia and how does it present?

Answer 8

Underdevelopment of the cerebellum; causes motor incoordination, tremor, and balance issues (e.g., “wobbly cats”).

Question 9

What are the main components of the basal ganglia?

Answer 9

• Striatum (caudate + putamen)
• Globus pallidus (GPe, GPi)
• Subthalamic nucleus (STN)
• Substantia nigra (SNr, SNc)

Question 10

What are the functions of the basal ganglia?

Answer 10

• Action selection
• Movement initiation and scaling
• Procedural learning
• Motivation and affect regulation

Question 11

What are medium spiny neurons (MSNs)?

Answer 11

GABAergic projection neurons in the striatum; divided into D1 (direct pathway) and D2 (indirect pathway) types.

Question 12

What is the role of striatal cholinergic interneurons?

Answer 12

Tonically active neurons (TANs) that modulate striatal output.

Question 13

What are the three major basal ganglia pathways?

Answer 13

• Direct: Facilitates movement (D1 MSNs → GPi/SNr)
• Indirect: Inhibits movement (D2 MSNs → GPe → STN → GPi/SNr)
• Hyperdirect: Global inhibition (Cortex → STN → GPi/SNr)

Question 14

What is the effect of dopamine on basal ganglia pathways?

Answer 14

• D1 MSNs: Dopamine increases activity → promotes movement
• D2 MSNs: Dopamine decreases activity → also promotes movement

Question 15

What is the role of the subthalamic nucleus (STN)?

Answer 15

Only excitatory (glutamatergic) output in the basal ganglia; part of the indirect and hyper direct pathways.

Question 16

What is the function of the substantia nigra pars compacta (SNc)?

Answer 16

Produces dopamine; modulates striatal activity to facilitate movement.

Question 17

What are the motor symptoms of Parkinson’s disease?

Answer 17

• Bradykinesia
• Akinesia
• Rigidity
• Resting tremor

Question 18

What causes motor symptoms in Parkinson’s disease?

Answer 18

Loss of dopaminergic neurons in SNc → overactive indirect pathway and underactive direct pathway → movement suppression

Question 19

What are common treatments for Parkinson’s disease?

Answer 19

• Levodopa (L-DOPA): Dopamine precursor
• Deep Brain Stimulation (DBS): Targets STN or GPi to modulate output