1. The Brain, Speech and Language: Control circuits Dr Pedro Amarante Andrade

2. CONTROL CIRCUITS
Integrate and control the activities of the structures and pathways involved in motor performance
Key point: Neither the basal ganglia not the cerebellum project directly onto lower motor neurons.

3. CONTROL CIRCUITS CEREBELLUM AND BASAL GANGLIA
The cerebellum: coordinates motor and sensory information
Gets info from the cortex about what muscles SHOULD be doing, and compares this with what is ACTUALLY happening
The basal ganglia: involved in control of background movement, and initiation of movement patterns

4. THE CEREBELLUM
‘little brain’ in Latin

5. THE CEREBELLUM ‘little brain’ in Latin
Vestibulocerebellum = flocculonodular lobe

6. PROJECTION TO THE CORTEX
Cortex sends information to cerebellum via pontine nuclei
cerebellum send information back to the cortex via the thalamus
Cerebellum also receives sensory information from the brain stem and spinal cord (e.g. proprioceptive stimuli via spinocerebellar tracts)
The basal ganglia form a complex collection of nuclei also involved in a loop from cortex to basal ganglia to thalamus and back to the cortex

7. FUNCTIONS OF THE CEREBELLUM
Stores learned sequences of movements
Participates in fine tuning and co-ordination of movements produced elsewhere in the brain
Integrates all of these things to produce fluid and harmonious movements.
So prime task is to ensure smooth coordination of muscles

8. ANTERIOR CEREBELLUM Spinocerebellum
projection area for the spinocerebellar proprioceptive information
Receives input from muscle and joint receptors (Golgi tendon organs & muscle spindles) via spinocerebellar tracts
Regulates posture, gait and truncal tone.;
It is connected to the spinal cord and controls postural muscle activity by influencing muscle tone.

9. POSTERIOR CEREBELLUM Cerebrocerebellum
Connected to the contralateral cortex and thalamus
Lateral portions of the cerebellar hemispheres have a role in coordinating skilled, sequential voluntary muscle activity
Ensures that when one set of muscles initiates a movement, the opposing set acts as a brake, so that the body part in question arrives at its target precisely.

10. FLOCCULONODULAR LOBE Vestibulo Cerebellum
The oldest part phylogenetically so aka the archicerebellum;
Connects with the vestibule of the inner ear and is involved in balance.
Contains the which connects with the 4 vestibular nuclei in the brainstem
Modulates equilibrium (balance) and orientation of head and eyes
fastigial nucleus
vestibular nuclei

11. CEREBELLAR PEDUNCLES
mostly afferent from spinal cord and brainstem; efferent to vestibular mechanisms and reticular formation
Mainly efferent output via purkinje cells
afferent from pontine nuclei
Superior
Middle
Inferior
Fibre tracts enter/leave through the inferior, middle and superior cerebellar peduncles

12. CEREBELLAR ANATOMY

13. CEREBELLAR ANATOMY
Motor planning
Position sense
Feedback

14. CEREBELLAR CONTROL CIRCUITS 1 loop important in planning and programming learned movements
Primary motor & premotor regions
Pontine nuclei
Lateral cerebellar hemispheres
Deep cerebellar nuclei
Ventral thalamus

15. CEREBELLAR CONTROL CIRCUITS 2
Corticospinal/
Corticobulbar
fibres
Intermediate cerebellar hemispheres
Deep cerebellar nuclei
Ventral thalamic nuclei
Primary motor cortex

16. CEREBELLAR CONTROL CIRCUITS
& premotor regions
Primary motor cortex
Corticospinal/
Corticobulbar
fibres
Pontine nuclei
Ventral thalamus
Deep
cerebellar
nuclei
Lateral cerebellar hemispheres
Intermediate cerebellar hemispheres

17. FUNCTIONS OF CEREBELLAR CONTROL CIRCUITS
Coordinate the timing between the single components of a movement
Scale the size of muscular actions
Coordinate the sequence of agonists and antagonist

18. CEREBELLAR SPEECH MOTOR CONTROL SUMMARY:
Cortex sends preliminary advance information referring intended speech goals to cerebellum
These preliminary speech commands are provisional, imprecise and in excess of those needed to accomplish speech goal
Cerebellum is thus ‘primed’ to check the adequacy of the outcome, based on sensory information coming in from the periphery (i.e. muscle spindles, joint and tendon sensors)
Cerebellum updates the motor output from the cortex to help smooth the actions of agonist/antagonist muscle contractions

19. BASAL GANGLIA CIRCUITS

20. BASAL GANGLIA CIRCUITS
Important in generating components of motor programmes for speech
Cortex initiates impulses in excess of requirements to produce the motor act
Basal ganglia is modulate through inhibition these impulses
Important in regulating muscle tone, goal directed activities, automatic activities

21. ANATOMY OF THE BASAL GANGLIA

22. ANATOMY OF THE BASAL GANGLIA

23. ANATOMY OF THE BASAL GANGLIA

24. BASAL GANGLIA CONTROL CIRCUITS
Selectively activates and inhibits movements. Provides internal cues for planning and refining slow continuous movement

25. BASAL GANGLIA CONTROL CIRCUITS
Caudate nucleus and putamen (the striatum): act together as a functional unit - INPUT
Globus pallidus interna and substantia nigra pars reticulata - main OUTPUT
Globus pallidus externa, Sub thalamic nucleus, and substantia nigra pars compacta - intermediate

26. BASAL GANGLIA CONTROL CIRCUITS Two Loops
Direct = responsible for activating movement overall excitatory
Indirect = stopping unwanted movement overall inhibitory
The two pathways operate together to provide balanced control of descending pathways.
NB Do not confuse these loops with the direct/indirect activation pathway

27. TWO LOOPS

28. NEUROTRANSMITTERS GABA (gamma aminobutyric acid) inhibitory -
Glutamate excitatory +
Ach (acetylcholine) - synapse in the striatum – excitatory +
Dopamine (substantia nigra) neuromodulatory
The balance of these is crucial to normal functioning of the loops and therefore motor output

29. DIRECT/INDIRECT PATHWAY OF BASAL GANGLIA
Direct = Making movement (excitatory)
Indirect = not moving (inhibitory)

30. DIRECT/INDIRECT PATHWAY OF BASAL GANGLIA
CORTEX
Direct = Promoting movement (excitatory)
Striatum
Thalamus
Aim = Reduce the natural inhibited state of the Thalamus :o(
Globus Pallidus
Subthalamus
Thalamus always wants to excite the cortex!
Glutamate (+)
GABA (-)
Substantia nigra
Dopamina

31. DIRECT/INDIRECT PATHWAY OF BASAL GANGLIA
CORTEX
Indirect = not moving (inhibitory)
Striatum
Thalamus
Aim = Avoid unwanted movement (Thalamus and Subthalamus) :O(
Globus Pallidus
Subthalamus
Thalamus always wants to excite the cortex!
Glutamate (+)
GABA (-)
Substantia nigra
Dopamina

32. DIRECT/INDIRECT LOOPS OF BASAL GANGLIA
Premotor/motor cortex
Striatum
External globus pallidus
Thalamus
Substantia nigra
Direct loop
Indirect loop
Subthalamic nucleus
Internal globus pallidus
PATHWAYS
GREEN = EXCITATORY
RED = INHIBITORY

33. NEUROMODULATORY EFFECT OF DOPAMINE
Direct Pathway: Stimulates
Indirect Pathway: Inhibits
Overall Excitatory

34. OTHER FUNCTIONS/LOOPS OF THE BASAL GANGLIA
An executive loop may regulate the initiation and termination of cognitive processes such as planning, working memory, and attention.
The limbic loop may regulate emotional behaviour.
The deterioration of cognitive and emotional function in both Huntington's disease and Parkinson's disease could be the result of disruption of these non-motor loops.

36. SUMMARY OF MOTOR PATHWAYS

37. SAME TYPICAL EXAMS QUESTIONS
Which of the two following components of the basal ganglia form a functional unit?
putamen and globus pallidus
Substantia nigra and putamen
Putamen and caudate nucleus
2. Complete the following: the lentiform nucleus is composed of……………………………………………….

38. 3. Which of the following statements is NOT true of the functions of the cerebellum?
Stores learned sequences of movements
Ensures smooth coordination of muscles
Regulates postural adjustments during skilled movements

39. 4. In addition to its role in movement control, list 2 other posited functions of the basal ganglia

40. WHAT TO DO NOW
Read the scanned chapter by Ellison (2012), chapter 6, Moving On. This should consolidate your understanding of movement, and the complex pathways involved.
Chapter 10 in Atkinson and McHanwell provides a more comprehensive summary.
Chapter 2 in Duffy (2007), a text you will use next year also has a good summary