The document discusses the role of the cerebellum in motor coordination. It describes how the cerebellum modifies movements by receiving information from the motor cortex and sending information back via the thalamus. The cerebellum is involved in coordination of voluntary movements, maintenance of balance and posture, motor learning, and cognitive functions. Cerebellar disorders, such as strokes and hereditary ataxias, can cause ataxia or lack of coordination in movements. Clinical features of cerebellar disorders include ataxic gait, intention tremor, dysmetria, and nystagmus.

1. Y2S2 Locomotion module
Coordination of movement
and Cerebellum
Prof. Vajira Weerasinghe
Professor of Physiology
Faculty of Medicine
University of Peradeniya
(www.slideshare.net/vajira54)

2. Objectives
1. Discuss the role of the cerebellum on motor
coordination
2. Explain giving examples how coordination is
affected in neurological disease

3. Cerebellum
• modify movement
• receive information from the
motor cortex
• send information back to cortex
via the thalamus

4. Functional significance of
cerebellum
• Coordination of voluntary movements
• Maintenance of balance and posture
• Motor learning
• Cognitive functions

6. Lobes
• Anterior lobe and part of posterior lobe
– receives information from the spinal cord
• Rest of the posterior lobe
– receives information from the cortex
• Flocculonodular lobe
– involved in controlling the balance through vestibular
apparatus

7. Zones
• Lateral zone
– this is concerned with overall planning of sequence and timing
• Intermediate zone
– control muscles of upper and lower limbs distally
• Vermis
– controls muscles of axial body, neck, hip

8. Inputs
• Corticopontocerebellar
– from motor and premotor cortex (also sensory cortex)
• Olivocerebellar
– from inferior olive
• Vestibulocerebellar
– to the flocculonodular lobe
• Reticulocerebellar
– to the vermis
• Spinocerebellar tracts
– dorsal spinocerebellar tracts
• from muscle spindle, prorpioceptive mechanoreceptor (feedback
information)
– ventral spinocerebellar tarcts
• from anterior horn cell
– excited by motor signals arriving through descending tracts (efference copy)

9. Outputs
• through deep cerebellar nuclei: dentate,
fastigial, interpositus
– 1. vermis -> fastigial nucleus -> medulla, pons
– 2. intermediate zone
-> nucleus interpositus
-> thalamus -> cortex
-> basal ganglia
-> red nucleus
-> reticular formation
– 3. lateral zone -> dentate nucleus
-> thalamus -> cortex

12. Neuronal circuitry of the cerebellum
• Main cortical cells in cerebellum are known as
Purkinje Cells (large cells)
• There are about 30 million such cells
• These cells constitute a unit which repeats
along the cerebellar cortex

16. Functional unit of the cerebellar
cortex
• a Purkinje cell
• a deep nuclear cell
• inputs
• output from the deep nuclear cell

17. Purkinje cell
inhibition
excitation excitation
Input
from Inferior
olive
Granule cells
Input
from other
afferents
Climbing
fibre
Mossy fibre
Deep nuclear
cell
Output

18. • Even at rest, Purkinje cells & deep nuclear cells
discharge at 40-80 Hz
• afferents excite the deep nuclear cells
• Purkinje cells inhibit the deep nuclear cells

19. Functions of cerebellum
• planning of movements
• timing & sequencing of movements
• control of rapid movements such as walking
and running
• calculates when does a movement should
begin and stop

20. Overview of motor system
hierarchy
1. Motor areas in the cerebral cortex

21. Overview of motor system
hierarchy
1. Motor areas in the cerebral cortex
2. Brainstem

22. Overview of motor system
hierarchy
1. Motor areas in the cerebral cortex
2. Brainstem
3. Spinal cord
motor circuits
rhythmic movements reflexes voluntary movements

23. Overview of motor system
hierarchy
1. Motor areas in the cerebral cortex
2. Brainstem
3. Spinal cord
motor circuits
rhythmic movements reflexes voluntary movements

24. Overview of motor system
hierarchy
1. Motor areas in the cerebral cortex
Cerebellum Basal ganglia
2. Brainstem
3. Spinal cord
motor circuits
rhythmic movements reflexes voluntary movements

25. ‘Error correction’
• cerebellum receives two types of information
– intended plan of movement
• direct information from the motor cortex
– what actual movements result
• feedback from periphery
– these two are compared: an error is calculated
– corrective output signals goes to
• motor cortex via thalamus
• brain stem nuclei and then down to the anterior horn cell
through extrapyramidal tracts

26. • ‘Prevention of overshoot’
– Soon after a movement has been initiated
– cerebellum send signals to stop the
movement at the intended point (otherwise
overshooting occurs)
• Ballistic movements
– movements are so rapid it is difficult to decide
on feedback
– a high-velocity musculoskeletal movement,
such as a tennis serve or boxing punch,
requiring reciprocal coordination of agonistic
and antagonistic muscles
– rapid movements of the body, eg. finger
movements during typing, rapid eye
movements (saccadic eye movements)
– therefore the movement is preplanned

27. planning of movements
• mainly performed by lateral zones
• sequencing & timing
– lateral zones communicate with premotor areas, sensory
cortex & basal ganglia to receive the plan
– next sequential movement is planned
– predicting the timings of each movement
• compared to the cerebrum, which works entirely on a
contralateral basis, the cerebellum works ipsilaterally

28. Motor learning
• the cerebellum is also partly responsible for
learning motor skills, such as riding a bicycle
- any movement “corrections” are stored as part of
a motor memory in the synaptic inputs to the
Purkinje cell
- research studies indicate that cerebellum is a
pattern learning machine
- cellular basis for cerebellum-dependent motor
learning is know to be a type of long-term
depression (LTD) of the Purkinje cell synapses

29. Neurotransmitters
• Excitatory: glutamate
» (Climbing, mossy, parallel fibres)
• Inhibitory: GABA
» (Purkinje cell)
• Serotonin and Norepinephrine are also known
to be involved

30. Cerebellar disorders
• Examples
– Cerebellar stroke
– Hereditary spinocerebellar ataxia
– Alcoholic cerebellar degeneration

31. Features of cerebellar disorders
• Ataxia
– incoordination of movements
– difficulty in regulating the force, range, direction,
velocity and rhythm of movements
– It is a general term and may be manifested in any
number of specific clinical signs, depending on the
extent and locus of involvement
– limb movements, gait, speech, and eye movements
may be affected

32. Features of cerebellar disorders
• ataxic gait
• broad based gait
• leaning towards side of the lesion
• dysmetria
• cannot plan movements
• abnormal finger nose test
• past pointing & overshoot
• cannot stop at the intended point and thus overshoot
results

33. Features of cerebellar disorders
• decomposition of movements
• movements are not smooth
• decomposed into sub-movements
• intentional tremor
• at rest: no tremor
• when some action is performed: tremor starts

34. Features of cerebellar disorders
• dysdiadochokinesis
• unable to perform rapidly alternating movements
• dysarthria
• slurring of speech
• scanning speech
• nystagmus
• oscillatory movements of the eye

35. Features of cerebellar disorders
• hypotonia
– reduction in tone
• particularly in pure cerebellar disease
• due to lack of excitatory influence on gamma motor
neurons by cerebellum
• pendular jerks
• legs keep swinging after a tap
• rebound
• increased range of movement with lack of normal recoil to
original position

36. Features of cerebellar disorders
• titubation
• head tremor
• truncal ataxia
• patients with disease of the vermis and flocculonodular
lobe will be unable to stand at all as they will have truncal
ataxia

37. Cerebellar degeneration

38. Spino Cerebellar Ataxia (SCA)
• Hereditary
• May be autosomal dominant or recessive
• About 50 types of spinocerebellar ataxia present
• Some types can be pure cerebellar
• Ataxia results from variable degeneration of neurons
in the cerebellar cortex, brain stem, spinocerebellar
tracts and their afferent/efferent connections

39. Alcoholic Cerebellar Degeneration
• Estimated overall prevalence of alcohol dependence is
0.5–3% of the population in Europe or USA
• Central and peripheral nervous systems are the two
principal targets
• Chronic alcohol ingestion can impair the function and
morphology of many brain structures particularly
cerebellum

40. Clinical examination of cerebellar
functions
• Gait (broad-based)
• Muscle power (normal)
• Muscle tone (hypotonia)
• Finger-nose test (abnormal)
• Heel-knee-shin test (abnormal)
• Rapid alternating movements (abnormal)
• Speech (dysarthria)
• Eye movements (nystagmus)
• Reflexes (pendular)
• Rebound phenomenon