JC - Central Pattern Generators

Question 1

Why do we offload tasks from the brain?

Answer 1

Expense (energy & focus)

• Evidence for an attention/energy budget

Latency (“speed”)
[monosynaptic ~30 ms
visuomotor ~ 100-200 ms]

Question 2

What are Central Pattern Generators and where are they found

Answer 2

Central pattern generators (CPGs) are circuits in self-contained integrative nervous systems, like the ENS, that generate repetitive patterns of motor behaviour

• Found in invertebrates to vertebrates

Question 3

Describe the locomotion examples in leeches, lampreys, dogs, and cats, highlighting the role of CPGs

Answer 3

Leeches exhibit coordinated swimming movements with interconnected neurons

Lamprey spinal cords have repeated circuit patterns with reciprocal inhibition

Cats, even after spinal cord transection, hindlimbs produce cyclic locomotion, indicating the presence of spinal circuits and CPGs

Question 4

What is the human basal ganglia and how does it work?

Answer 4

Controls initiation of movement

Cortex → Striatum → Basal ganglia (globus pallidus) → The thalamus → Motor cortex

Question 5

What is the role of the Human Basal Ganglia in movement initiation, and what problems can arise if this process is impaired?

Answer 5

• Stimulate striatum
• Inhibits globus pallidus
• Disinhibits VA/Vl complex of thalamus
• Stimulates motor cortex

Problems arise if unable to inhibit the inhibitors (Hyper-inhibition) - Parkinson’s

Question 6

How do Dopamine and the Corticospinal Tracts contribute to motor function?

Answer 6

Dopamine boosts the effects of the striatum

Corticospinal Tracts terminate among pools of local circuit neurones in the Ventral Horn of the spinal cord

Question 7

What is the role of the Cerebellum in motor activity, and how does it function in integrating sensory feedback?

Answer 7

Integrates sensory feedback for motor activity

Inputs:

• Intentional actions from Cortex
• Actual actions from the periphery

Function:

• Compare intention to actual movement and generate correction signals

Output:

• Correction signals into brain stem motor centres

Question 8

What are the important points from this lecture? (4)

Answer 8

1. Cortical neurones have limited direct affect on lower motor neurone activity but control ‘intentional’ activity
2. The Basal Ganglis and Cerebellum modulate locomotor commands
3. Basal Ganglia controlling INITIATION of movement
4. Cerebellum INTEGRATES sensory information with INTENTIONAL and sends correctional information to Brain Stem and motor cortex