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Human Physiology · Nervous system and exercise

Motor Control: Cortex, Basal Ganglia, Cerebellum

Smooth movement needs a plan, a command and constant correction. This page explains how the motor cortex, basal ganglia and cerebellum work together, what goes wrong in stroke, Parkinson disease and ataxia, and how practice changes the motor system.

10Sections
5Figures
3Tables
10Questions

Part 9 · Nervous System and Exercise · Chapter 43 of 47

Learning objectives

By the end of this page you should be able to:

  • Describe the hierarchy and parallel loops of motor control.
  • Describe the motor cortex and corticospinal tract.
  • Explain direct and indirect basal ganglia pathways and dopamine.
  • Explain the cerebellum as a comparator and its role in learning.
  • Recognise the signs of cortical, basal ganglia and cerebellar lesions.
  • Summarise evidence on task training after stroke and physiotherapy in Parkinson disease.

Why it matters

Stroke, Parkinson disease and cerebellar disorders are among the commonest neurological conditions physiotherapists treat. Each affects a different part of the motor system and needs a different approach.

Understanding motor control turns a list of signs into a treatment plan.

Organisation

Figure 1 · Organisation of motor control

Hierarchy of cortex, brainstem and spinal cord with basal ganglia and cerebellar side loops Association cortex sets goals, premotor and motor cortex select and command movement, the brainstem controls posture and the spinal cord contains reflexes and pattern generators. The basal ganglia and cerebellum form side loops through the thalamus that shape cortical output. Association cortexgoal and planPremotor and motor cortexselect and commandBrainstemposture, orientationSpinal cordreflexes, pattern generatorscorticospinaltract (direct)Basal gangliaselect, scale, startCerebellumtiming, coordination,error correctionloop via thalamusloop via thalamus
Hierarchy plus loops. The side loops do not send commands to muscles directly; they shape what the cortex and brainstem send.

The primary motor cortex holds a map of the body, with large areas for the hand and face. Most corticospinal fibres cross in the medullary pyramids and control skilled, fractionated movement, especially of the hands.

For tract anatomy, see the Human Anatomy pages.

The basal ganglia

Figure 2 · Basal ganglia: go and no-go

Direct and indirect basal ganglia pathways and the effect of dopamine Motor cortex drives the striatum. The direct pathway releases the output nuclei's brake on the thalamus, allowing movement; the indirect pathway tightens the brake. Dopamine from the substantia nigra favours the direct pathway. The thalamus projects back to cortex. Motor cortexStriatumDirect path: GOIndirect path: NO-GOGPi / SNr outputtonic brake on thalamusThalamusback to cortexSNc dopaminehelps GO, damps NO-GOreleases braketightens brake
Parkinson disease. Loss of dopamine leaves the brake on: movements become small, slow and hard to start. Simplified schematic.
DisorderBasal ganglia changeMovement result
Parkinson diseaseDopamine loss; too much brakingBradykinesia, rigidity, rest tremor, small steps
Huntington diseaseLoss of indirect-path neurons; too little brakingChorea, involuntary movements
HemiballismusSubthalamic nucleus lesionFlinging movements of one side

External cues such as rhythm, lines on the floor and counting help people with Parkinson disease bypass the faulty internal timing.

The cerebellum

Figure 3 · The cerebellum as comparator

Cerebellum comparing intended and actual movement to correct errors The motor cortex sends a command to the muscles and a copy to the cerebellum. Sensory feedback reports the actual movement. The cerebellum compares the two and sends an error signal that corrects ongoing and future commands. Motor cortexintended movementCerebellumcompares intendedwith actualMuscles and limbactual movementProprioceptors, vestibular,vision: feedbackcommandcopy of planerror signal correctsthe next command anddrives motor learning
Cerebellar damage causes ataxia, intention tremor, dysmetria and dysdiadochokinesia on the same side as the lesion. Schematic.
SignDescription
AtaxiaUnsteady, broad-based gait and poorly coordinated limbs
DysmetriaOver- or under-shooting a target
Intention tremorTremor increasing as a target is approached
DysdiadochokinesiaDifficulty with rapid alternating movements
Nystagmus and dysarthriaEye and speech coordination problems

Motor learning and recovery

Practice changes synaptic strength in cortex, basal ganglia and cerebellum. After stroke, surviving areas can take over lost functions when they are used intensively.

French and colleagues reviewed 33 trials of repetitive task training after stroke [1]. Practising whole functional tasks improved arm, hand, lower limb and walking outcomes [1].

Figure 4 · Practice the task after stroke

Effects of repetitive task training on arm, hand, lower limb and walking outcomes after stroke Repetitive task training improved arm function by a standardised mean difference of 0.25, hand function 0.25, lower limb function 0.29 and functional ambulation 0.35, with confidence intervals at or above zero. Walking distance rose by about 35 metres. Arm function0.25Hand function0.25Lower limb function0.29Functional ambulation0.3500.20.40.60.8Standardised mean difference (right favours task training)Walking distance also rose by about 35 m; 33 trials, 1,853 people [1]
Small but real gains. Benefits lasted up to six months and did not depend on dose, task type or time since stroke in this review [1].

In Parkinson disease, Tomlinson and colleagues pooled 39 trials of physiotherapy versus no intervention [2]. Gait speed, balance and disease rating scores improved in the short term [2].

Figure 5 · Physiotherapy in Parkinson disease

Pooled short-term benefits of physiotherapy in Parkinson disease Thirty-nine trials with 1,827 participants. Physiotherapy improved gait speed by 0.04 metres per second, Berg balance score by 3.71 points and Parkinson disease rating scale total and motor scores by 6.15 and 5.01 points. Trials / participants39 / 1,827Gait speed+0.04 m/sBerg Balance Scale+3.71 pointsUPDRS total−6.15 points (better)UPDRS motor−5.01 points (better)Physiotherapy versus no intervention; short-term benefits, little difference between techniques [2]
Physiotherapy helps in the short term. Different techniques had similar effects; long-term trials are needed [2].

Practical skill

Make practice specific, repeated and challenging. In Parkinson disease, add external cues and large-amplitude movements. In ataxia, practise balance and coordination with gradually reduced support.

Clinical relevance for the physiotherapist

  • Stroke. Practise real tasks repeatedly [1].
  • Parkinson disease. Physiotherapy improves gait, balance and motor scores [2].
  • Cerebellar ataxia. Train balance and coordination; ensure safety.
  • Localise. Match signs to cortex, basal ganglia or cerebellum.
  • Measure. Track gait speed and balance scores.

Assessment and application

FindingLikely siteApproach
Weak hand, brisk reflexes after strokeMotor cortex or corticospinal tractTask-specific practice [1]
Slow, small movements, rest tremor, freezingBasal gangliaCueing, amplitude training [2]
Intention tremor and broad-based gaitCerebellumBalance and coordination training
Freezing at doorwaysBasal ganglia timingVisual or auditory cues

Common mistakes

  • Practising isolated movements instead of tasks [1].
  • Too few repetitions to drive learning.
  • Assuming Parkinson disease needs only medication [2].
  • Confusing cerebellar tremor with rest tremor.
  • Ignoring falls risk in ataxia.

Exam preparation

Long answer

Describe the functions of the basal ganglia and cerebellum. Add a note on their disorders.

  • Organisation of motor control (Figure 1).
  • Basal ganglia circuits and dopamine (Figure 2).
  • Cerebellum as comparator (Figure 3).
  • Disorders (tables).
  • Rehabilitation evidence [1, 2].

Short notes

  • Corticospinal tract.
  • Parkinson disease.
  • Cerebellar signs.
  • Repetitive task training [1].

Viva and practical

  • “Which neurotransmitter is lost in Parkinson disease?” — dopamine.
  • “On which side are cerebellar signs?” — the same side as the lesion.
  • “Does physiotherapy help Parkinson disease?” — yes, short-term gains [2].
  • OSCE: perform finger-nose and heel-shin tests.

Current evidence

Exam and traditional teaching

Motor control is a fixed hierarchy; lost function is lost permanently.

What the evidence adds

Repetitive task practice improves function after stroke [1].

Physiotherapy improves gait and balance in Parkinson disease [2].

What the student should understand

The motor system learns. Rehabilitation is structured, repeated practice.

Check yourself

10 questions on this page. Tap one to see the answer and the reasoning.

Q1. Repetitive task training after stroke improved walking distance by about:
  1. (A) 3 m
  2. (B) 35 m
  3. (C) 350 m
  4. (D) No change

Answer: (B) Mean difference 34.8 m [1].

Q2. How many trials were in the repetitive task training review?
  1. (A) 3
  2. (B) 33
  3. (C) 333
  4. (D) 3,000

Answer: (B) Thirty-three trials with 1,853 participants [1].

Q3. Benefits of repetitive task training were found up to:
  1. (A) One day
  2. (B) Six months after treatment
  3. (C) Ten years
  4. (D) Never

Answer: (B) Effects were sustained up to six months but not beyond [1].

Q4. Were effects modified by dosage of task practice or time since stroke?
  1. (A) Yes, strongly
  2. (B) No, not in this review
  3. (C) Only dose mattered
  4. (D) Only time mattered

Answer: (B) Effects were not modified by type, dose or time since stroke [1].

Q5. The quality of evidence for task training improving arm function was:
  1. (A) High
  2. (B) Low
  3. (C) None
  4. (D) Very high

Answer: (B) Low-quality evidence, SMD 0.25 [1].

Q6. Physiotherapy in Parkinson disease improved the Berg Balance Scale by about:
  1. (A) 0.4 points
  2. (B) 3.7 points
  3. (C) 37 points
  4. (D) No change

Answer: (B) Berg score improved by 3.71 points [2].

Q7. Gait speed improved with physiotherapy in Parkinson disease by about:
  1. (A) 0.04 m/s
  2. (B) 0.4 m/s
  3. (C) 4 m/s
  4. (D) No change

Answer: (A) Speed improved by 0.04 m/s [2].

Q8. The UPDRS motor subscore changed by about:
  1. (A) −5 points (better)
  2. (B) +5 points (worse)
  3. (C) −50 points
  4. (D) No change

Answer: (A) Motor subscore improved by 5.01 points [2].

Q9. Different physiotherapy techniques for Parkinson disease:
  1. (A) Differed greatly in effect
  2. (B) Showed little difference in treatment effects
  3. (C) Were all harmful
  4. (D) Were not compared

Answer: (B) There was little difference between techniques [2].

Q10. The benefits of physiotherapy in Parkinson disease were shown mainly:
  1. (A) In the short term
  2. (B) Over 20 years
  3. (C) Only after surgery
  4. (D) Not at all

Answer: (A) Physiotherapy has short-term benefits; longer-term trials are needed [2].

Quick review

Key takeaways

  • Motor control: hierarchy plus basal ganglia and cerebellar loops.
  • Basal ganglia: direct path GO, indirect path NO-GO; dopamine helps GO.
  • Cerebellum compares intended and actual movement; lesions are ipsilateral.
  • Task training improves arm, leg and walking after stroke [1].
  • Physiotherapy improves gait speed, balance and UPDRS in Parkinson disease [2].
  • Use cues, amplitude and repetition.

Further reading

SourceWhy it earns its place
French B et al. — Cochrane, 2016Repetitive task training [1]
Tomlinson CL et al. — BMJ, 2012Physiotherapy in Parkinson disease [2]
Shumway-Cook and Woollacott, Motor ControlTheory and practice

References

  1. French B, Thomas LH, Coupe J, et al. Repetitive task training for improving functional ability after stroke. Cochrane Database of Systematic Reviews. 2016;11(11):CD006073. doi:10.1002/14651858.CD006073.pub3 PMID 27841442 Systematic review and meta-analysis
  2. Tomlinson CL, Patel S, Meek C, et al. Physiotherapy intervention in Parkinson’s disease: systematic review and meta-analysis. BMJ. 2012;345:e5004. doi:10.1136/bmj.e5004 PMID 22867913 Systematic review and meta-analysis

Related topics

Reviewed by the Physiotherapist India Team. · Human Physiology contents