HUF 2-46 Locomotion and functions of the cerebellum

Question 1

Gait cycle

Answer 1

Stance phase (60%)

• heel strike
• foot flat
• mid-stance
• push-off

Swing phase (40%)

• acceleration
• mid-swing
• deceleration

Question 2

Deafferentation experiment

Answer 2

• Locomotor rhythmic activities can be generated w/o sensory inflow to CNS
• Induced by transection of spinal cord after deafferentation

Question 3

Central pattern generator (CPG)

Answer 3

• Neuronal network w/i CNS
• Generates rhythmic motor activity patterns w/o requiring sensory input
• “Half centre” model
• Mutually inhibitory
• Inhibitory output from a centre during each cycle fatigues after a time interval

=> activation of the other centre

(e.g. flex. inhibited => ext. activated)

Question 4

Descending inputs from brainstem can initiate CPG rhythmic activities

Answer 4

1. MLR (midbrain locomotor region)
2. Subthalamic locomotor region
3. Pontine reticular formation

Question 5

Role of proprioception on gait rhythm

Answer 5

• Gait rhythm does not require sensory input for generation
• Constantly regulated by proprioception
• Stretching hip flexor (iliopsoas) to mimic end of stance phase

=> early initiation of swing induced by stretch

Question 6

Motor cortex modulates locomotor pattern;

Vision is needed for precise walking

Answer 6

• Short term working memory needed for steady walking on surfaces with obstacles (structure and height)
• Posterior parietal cortex for visually guided locomotion

Question 7

Spinal patterning networks under constant sensory and descending regulations

Answer 7

Question 8

Function of cerebellum

Answer 8

• Modulation to motor outputs for flexibility and precision of movement via loops with spinal cord and cortex
• Cerebellar cortex (3 layers with regular, repetitive circuitries)
• Inputs: mossy fibre, climbing fibre w

=> Intermediate: granule cell and other cell types

=> Output: Purkinje cell

Question 9

Functional anatomy of cerebellum

Answer 9

Question 10

Function of spinocerebellum

Answer 10

Question 11

Function of cerebrocerebellum

Answer 11

Motor planning and precise timing of movement

Question 12

Cerebellar diseases

Answer 12

• Movement deficit
• Errors in both motor planning and execution
  e. g. Range of movement error

Patterned movement error

Delayed movement

Ataxia: lack of coordination during execution of multi-joint movement