Lec 5: Cerebellum

Question 1

Motor Pathways Overview

Answer 1

-Cerebellum receives from cerebral cortex (1) and spinal cord (2) for motor coordination and correction
-Cerebellum sends to cortex (via thalamus VPL) and to SC (via brain stem)
-Cortex receives from thalamus
-Cortex sends to SC (via brain stem), BG, and cerebellum

Question 2

Motor Control and Cerebellum

Answer 2

1. maintenance of balance and posture (via vestibular info/proprioception)
2. coordination of multiple motor groups/movements
3. Proprioception input from MS feedback
4. Postural adjustments (based upon load) unconsciously from GTO
5. Sensory processing
6. Adaptability
7. Automaticity (esp. in posture)
8. Motor commands not initiated in cerebellum (modifies motor activity for accuracy

Question 3

Cerebellum role in motor learning

Answer 3

-adapting and fine tuning motor programs to make accurate movements via trial and error process

Question 4

Cerebellum role in cognitive functions

Answer 4

-functions (like language), extend beyond motor control but not yet understood

Question 5

Cerebellum requires…

Answer 5

proprioception from muscle spindles and vestibular information for control of balance and equilibrium

Question 6

Anticipatory function of cerebellum

Answer 6

Anticipates output of motor command (especially in coordination of multiple muscles across several joint

Question 7

Cerebellum function in eye reflex

Answer 7

Fixation on target and eye coordination

Question 8

Cerebellum sensorimotor coordination

Answer 8

-predicts the sensory outcome of our movements/actions
-creates replica of our movement in time and produces :likeness of pattern”
-if motor performance has errors (cerebellum corrects via error based learning)
-timing is critical, onset and offset of muscle activation, direction of movement

Question 9

Cerebellum volume

Answer 9

contains over 50% of total number of neurons in brain

Question 10

Cerebellum input and modulation

Answer 10

Input: from vestibular receptors and muscle proprioceptors (MS and GTO)
Modulates: to motor neurons (to compensate for shifts in body position or changes in load upon muscles)

Question 11

Flocculonodular Lobe

Answer 11

-major transport for vestibular information to cerebellum
-Equilibrium, balance, posture

Question 12

Cerebellum Regional Function

Answer 12

Lateral hemispheres: motor planning for extremities, planning and initiating of movements
Intermediate hemispheres: distal limb coordination
Vermis: proximal limb and trunk coordination
Flocculonodular lobe: balance and vestibulocular reflexes

Question 13

Deep cerebellar nuclei input to and output from cerebellum

Answer 13

Output: Purkinje cells
Input: Climbing fibers and mossy fibers

Question 14

Main Cerebellar Input Pathways

Answer 14

UNCONSCIOUS INPUT, DIRECT
1. Vestibular inputs: Balance and equilibrium
2. Motor, sensory, and visual inputs: from all regions (corticopontine fibers)

Question 15

1. Vestibular-Cerebellar Connections

Answer 15

-DIRECT connection from vestibular receptors to flocculonodular lobe of cerebellum
-Vestibular receptors –> Vestibular ganglion –> Vestibular complex in Rostral Medulla –> Cerebellum

Question 16

2. Periphery (LL and trunk) Connections

Answer 16

1a: Dorsal Spinocerebellar Tract: from L2 and below, stays ipsilaterally, large myelinated axons carrying proprioceptive, touch, and pressure from LL and trunk
1a: Cuneo Spinocerebellar Tract: from C8 and above, stays ipsilaterally, large myelinated axons carrying proprioceptive, touch, and pressure sensation from LL and trunk
1b: Ventral Spinocerebellar Tract: from L2 and below, double crosses over, carrying info for coordinated movement and posture of entire LL
1b: Rostral Spinocerebellar Tract: from C8 and above, stays ipsilaterally, carrying info for coordinates movement and posture of entire LL

Question 17

Cerebellum Output Pathways

Answer 17

INDIRECT connections to motor system
1. DCN –> red nucleus –> SC
2. DCN –> VLN –> cortex (pre motor, supplementary, and pre frontal association area)

Question 18

Spinocerebellar Tract Origin of Input

Answer 18

Dorsal SCT: Leg proprioceptors
Ventral SCT: Leg interneurons
Cuneal SCT: Arm proprioceptors
Rostral SCT: Arm interneurons

Question 19

Vestibular Input Origin

Answer 19

Vestibular system

Question 20

Lesions of cerebellum

Answer 20

-remain ipsilateral to side of lesion (Ventral SCT crosses twice)
(Dorsal, cuneo, and rostral stay unilateral)

Question 21

Deficits of patients with cerebellar dysfunction

Answer 21

-uncoordinated voluntary movements and problems maintaining balance and posture
-decomposition of movement
-intention tremor

Question 22

Decomposition of Movement

Answer 22

-unable to produce coordinated, smooth movements
-loss of feedforward mechanism (input from spindle ab speed and GTO ab force) does not allow for temporal/timing of activated muscle sequence of activation, force or awareness in space

Question 23

Intention Tremor

Answer 23

-when making movement to a target pt produces involuntary movement tremor
-tremor increases as they approach closer to target
-e.g. starts out direct and is it gets closer hand moves back and forward

Question 24

Cerebellar Exams: Speed, coordination, timing

Answer 24

e.g. heel to shin and finger to nose
Dysrhythmia: abnormal timing
Dysmetria: overshoot or past pointing

Question 25

Cerebellar Exams: Rapid Alternating movements

Answer 25

Dysdiadochokinesia: RAM (sup/pro)
Overshooting: holding a test position and suddenly letting go
Action tremor or Intention Tremor
Truncal Ataxia

Question 26

Cerebellar Disorder Deficit

Answer 26

Postural Dysfunction
-high fall risk
-loss of automatic movements
-loss of ankle, hip strategies
-static and dynamic posture, especially

Question 27

Deficits in cerebellar function

Answer 27

Hypotonia: low tone from loss of MS and GTO input
Slow generation of force: unable to produce timely force generation (5/5 strength t/o)
Loss of RAM: inability to produce RAM patterns and alternating mvmt patterns
Deficits in Motor Learning: loss of ability to anticipate (feedforward) or correct (feedback) bc loss of proprioceptive, sensory, and muscular force