1. Bear: Neuroscience: Exploring the Brain, 3e
Chapter 14: Brain Control of Movement

2. Introduction The brain influences activity of the spinal cord
Voluntary movements
Hierarchy of controls
Highest level: Strategy
Middle level: Tactics
Lowest level: Execution
Sensorimotor system
Sensory information used by all levels of the motor system

3. Descending Spinal Tracts
Axons from brain descend along two major pathways
Lateral Pathways
Ventromedial Pathways

4. Descending Spinal Tracts
The Lateral Pathways
Voluntary movement - originates in cortex
Components
Corticospinal tract (pyramidal tract)
Rubrospinal tract

5. Descending Spinal Tracts
The Lateral Pathways (Cont’d)
The Effects of Corticospinal Lesions
Deficit in fractionated movement of arms and hands
Paralysis on contralateral side
Recovery if rubrospinal tract intact
Subsequent rubrospinal lesion reverses recovery

6. Descending Spinal Tracts
The Ventromedial Pathways
Posture and locomotion - originates in brain stem
The Vestibulospinal tract : head balance, head turning
The Tectospinal tract: orienting response

7. Descending Spinal Tracts
The Ventromedial Pathways
The Pontine and Medullary Recticulospinal Recticulospinal tract
Pontine: enhances antigravity reflexes
Medullary: liberates antigravity muscles from reflex

8. Descending Spinal Tracts
Summary

9. The Planning of Movement by the Cerebral Cortex
Motor Cortex
Area 4 and area 6 of the frontal lobe

10. The Planning of Movement by the Cerebral Cortex
Motor Cortex (Penfield)
Area 4 = “Primary motor cortex” or “M1”
Area 6 = “Higher motor area” (Penfield)
Lateral region  Premotor area (PMA)
Medial region  Supplementary motor area (SMA)
Motor maps in PMA and SMA
Similar functions; different groups of muscles innervated

11. The Planning of Movement by the Cerebral Cortex
Motor Cortex
Somatotopic organization of precentral gyrus (like postcentral gyrus)

12. The Planning of Movement by the Cerebral Cortex
The Contributions of Posterior Parietal and Prefrontal Cortex
Represent highest levels of motor control
Decisions made about actions and their outcome
Area 5: Inputs from areas 3, 1, and 2
Area 7: Inputs from higher-order visual cortical areas such as MT

13. The Planning of Movement by the Cerebral Cortex
The Contributions of Posterior Parietal and Prefrontal Cortex (Cont’d)
Anterior frontal lobes: Abstract thought, decision making and anticipating consequences of action
Area 6: Actions converted into signals specifying how actions will be performed
Per Roland Monitored cortical activation accompanying voluntary movement (PET)
Results supported view of higher order motor planning

14. The Contributions of Posterior Parietal and Prefrontal Cortex
Neuronal Correlates of Motor Planning
Evarts:Demonstrated importance of area 6 in planning movement
“ready”- Parietal and frontal lobes
“set”- Supplementary and premotor areas
“go”- Area 6

15. The Basal Ganglia
Basal Ganglia: Selection and initiation of willed movements

16. The Basal Ganglia Basal ganglia
Project to the ventral lateral (VLo) nucleus
Provides major input to area 6
Cortex
Projects back to basal ganglia
Forms a “loop”

17. The Basal Ganglia The Motor Loop:
Excitatory connection from cortex to putamen
Cortical activation
Excites putamen
Inhibits globus pallidus
Release VLo from inhibition
Activity in VLo influences activity in SMA

18. The Basal Ganglia The Motor Loop (Cont’d) Basal Ganglia Disorders
Parkinson’s disease: Trouble initiating willed movements due to increased inhibition of the thalamus by basal ganglia
Symptoms: Bradykinesia, akinesia, rigidity and tremors of hand and jaw
Organic basis: Degeneration of dopaminergic substantia nigra inputs to striatum
Dopa treatment: Facilitates production of dopamine to increase SMA activity

19. The Basal Ganglia The Motor Loop (Cont’d)
Basal Ganglia Disorders (Cont’d)
Huntington’s disease
Symptoms: Hyperkinesia, dyskinesia, dementia, impaired cognitive disability, personality disorder
Hemiballismus: Violent, flinging movement on one side of the body
Loss of inhibition with loss of neurons in caudate, putamen, globus pallidus

20. Initiation of Movement by the Primary Motor Cortex
Electrical stimulation of area 4
Contraction of small group of muscles
The Input-Output Organization of M1
Betz cells: Pyramidal cells in cortical layer 5
Two sources of input to Betz cells
Cortical areas
Thalamus
Coding Movement in M1
Activity from several neurons in M1 encodes force and direction of movement

21. Initiation of Movement by the Primary Motor Cortex
Coding Movement in M1
Recordings from a single cell in M1 illustrating “direction vector”

22. Initiation of Movement by the Primary Motor Cortex
Coding Movement in M1(Cont’d)
Movement of direction encoded by collective activity of neurons
Motor cortex: Many cells active for every movement
Activity of each cell: Represents a single “vote”
Direction of movement: Determined by a tally (and averaging)

23. Initiation of Movement by the Primary Motor Cortex
Coding Movement in M1(Cont’d)
Population Vectors

24. Control of saccadic eye movements by the Superior Colliculus
Computational map of Motor ‘error’
Motor error : Desired eye position – current eye position 30 Up 20 B
BC
AB
XA A 10 C 10 20 30
Right

25. Initiation of Movement by the Primary Motor Cortex
The Malleable Motor Map: Experimental rats
Microstimulation of M1 cortex normally elicits whisker movement
Cut nerve that supplies whisker muscles
Microstimulation now causes forelimb movement

26. The Cerebellum
Function: Sequence of muscle contractions; calibration and coordination.
Cerebellar lesions
Ataxia: Uncoordinated and inaccurate movements
Dysynergia: Decomposition of synergistic multijoint movements
Dysmetria: Overshoot or undershoot target

27. The Cerebellum
Anatomy of the Cerebellum

28. The Cerebellum Anatomy of the Cerebellum (Cont’d) Folia and lobules
Deep cerebellar nuclei: Cerebellar output
Relay cerebellar cortical output to brain stem structures
Vermis: Axial musculature
Contributes to ventromedial pathways
Cerebellar hemispheres: limb movements
Contributes to lateral pathways

29. The Cerebellum The Motor Loop Through the Lateral Cerebellum
Calibrated execution of planned, voluntary, multijoint movements

30. The Cerebellum The Motor Loop Through the Lateral Cerebellum
Pontine nuclei
Axons from layer V pyramidal cells in the sensorimotor cortex form massive projections to pons
Corticopontocerebellar projection
20 times larger than pyramidal tract

31. The Cerebellum The Motor Loop Through the Lateral Cerebellum
Cerebellum- “brain inside”
Learning
New motor programs created to ensure smooth movement

32. Concluding Remarks Example of the baseball pitcher
Walking: Ventromedial pathways
Ready to pitch
Neocortex, ventromedial pathways
Pitch signs and strategy
Sensory information engages parietal and prefrontal cortex and area 6

33. Concluding Remarks Example of the baseball pitcher (Cont’d)
Winds and throws
Increased basal ganglia activity (initiation)
SMA activity  M1 activation
Corticopontocerebellar pathways  Cerebellum
Cortical input to reticular formation  Release of antigravity muscles
Lateral pathway  engages motor neurons  action

34. End of Presentation