BASAL GANGLIA MOTOR PATHWAYS

1. BASAL GANGLIAMOTOR PATHWAYS DR. GALLATZ KATALIN

2. Basal Ganglia - Components of the basal ganglia - Function of the basal ganglia - Functional circuitry of the basal ganglia e.g., direct and indirect pathways, transmitters - Circuitry involved in movement disorders

3. Basal Ganglia • Striatum • Caudate nucleus • Putamen 2. Pallidum Globus pallidus external segment (GPe) Globus pallidus internal segment (GPi) • Ventral pallidum • accumbens nucleus • olfactory tubercle 4. Substantia Nigra Pars compacta (SNc) Pars reticulata (SNr) 5.Subthalamic nucleus (STN)

4. Main components of basal ganglia: STRIATUM - caudate nucleus,putamen, globus pallidus, - subthalamic nucleus, andthe substantia nigra. -nucleus accumbens and ventral pallidum

7. BASAL GANGLIA

8. Functions of basalganglia • Motor functions • Control of theeyemovements - basalganglia (BG) haveimportantroleincontrollingeyemovements. SC receives a stronginhibitory projection fromthe substantianigraparsreticulata • Motivation - (ventraltegmentalarea→ nucl. accumbens→ prefrontalcortex; dopamin; drugabuse and addiction) • Cognitivefunctions: - decisionmaking, choosingtheappropriatebehaviour (nucl. basalis; acetylcholin; Alzheimer’sdisease) • Emotionalreactions (amygdala-ventralstriatum)

9. ROLE OF THE BASAL GANGLIA IN MOTOR SYSTEM • Basal ganglia are involved in generation of • goal-directed voluntary movements: • Motor learning • Motor pattern selection

10. Input to basal ganglia

11. Lateral view Regions of cortical input to the basal ganglia Medial view

12. Output from the basal ganglia Midbrain

13. Output and internal circuitry Input

14. Medium-spiny neuron in the basal ganglia SN

15. Synaptic input to and output from striatal medium spiny neurons Smith and Bolam 1990

16. Medium spiny neuron projections

18. VA/VL Disinhibition *tonically active ~100 Hz * Cortex Direct pathway: facilitates movements Striatum Excitation (glutamate) Inhibition (GABA) * GPe STN GPi/SNr Brain stem/ Spinal cord Modified from Wichmann and Delong, Curr Opin Neurobiol. 6:751-758, 1996.

19. Basic Circuit of Basal Ganglia + + Gpe + Subth Cerebral Cortex Striatum INDIRECT PATHWAY DIRECT PATHWAY Gpi VA/VL thalamus

20. Direct and indirect pathways

21. Involvement of the cerebellum Frontopontine tract Temporooccipitopontine tr. Cerebellothalamic tract pontocerebellar tract

22. Prefrontal loop (Associative) Limbic loop Basal ganglia loops – motor and non-motor Motor loop

23. Motor control systems in the cortex PRIMARY MOTOR CORTEX– source of pyramidal tract neurones SUPPLEMENTORY MOTOR CORTEX- conception and initiation ofmovement. - lesions cause deficits in voluntary movement or speech PREMOTOR CORTEX- important in motor coordination. - lesions cause impairments in stability of stance, gait and hand coordination From: Biopsychology, JPJ Pinel

24. Primary motor cortex – somatotopic organization From: Biopsychology, JPJ Pinel

25. MOTOR SYSTEM PYRAMIDAL, EXTRAPYRAMIDAL???

26. Motor pathways The alpha-motoneuron is the final common pathway

27. Pyramidal and extrapyramidal systems Pyramidal and extrapyramidal systems can only be separated anatomically but not functionally!! None of the two systems can work properly alone, they constitute one motor system together!!!

28. PYRAMIDAL SYSTEM • Pyramidal system is the chief organizer and executor of voluntary movements. CORTICOSPINAL AND CORTICOBULBAR (CORTICONUCLEAR TRACT) TO THE MOTOR NUCLEI OF THE CRANIAL NERVES

29. crossed(lateral)uncrossed (ventral)

30. THE PYRAMIDAL SYSTEM • Pyramidal system is the chief organizer and executor of voluntary movements. • Upper motoneuronsare located in the cerebral cortex, while lower motoneurons can be found in the motor nuclei of cranial nerves or in the spinal ventral horn. • Descending axons of upper motoneurons that terminate in the motor nuclei of cranial nerves and in the spinal cord constitute the corticonuclear (corticobulbar) and corticospinal tracts. • The corticonuclear tract reaches the lower motoneurons of both sides (bilateral innervation), while corticospinal fibres target the lower motoneurons of the opposite side only (crossed pathway).

31. Motor pathways from the brainstem (EXTRAPYRAMIDAL TRACTS) Rubrospinal tr. • Extrapyramidal system includes all the motor centres and pathways that lie outside the pyramidal system and are beyond voluntary control.

32. rubrospinal tr. tectospinal tr. reticulospinal tr. Vestibulospinal tr. olivospinal tr. ??? Efferent extrapyramidal pathways from Dr. Kozsurek

33. Extrapyramidal pathways Tectospinal Rubrospinal Reticulospinal Vestibulospinal

34. Spinal motor pathways Tectospinal tract- coordinating head and eye movements as part of the optic reflexes Vestibulospinal tract- influences postural muscles Reticulospinal tract- projects from the reticular formation - inhibition or facilitation of movement Pyramidal tract- control most of our fine movements From : The Central Nervous System, P. Brodal Rubrospinal tract -from the red nucleus Olivospinal tract?? - from the inferior olive

35. TRANSVERSE SECTION SPINAL CORDMOTOR PATHWAYS 35

36. Role of the motor pathwaysfrom the brainstem • Extrapyramidal system: • coordinates movements of various groups of muscles both in space and time, • regulatesautomaticmovements consisting of periodic elements (e.g. walking, running, riding, driving a car, handwritingortyping, etc.), • controlsemotionalmovements, • helps to control posture and balance, • regulates muscle tone.

37. Overview of motor pathways

38. MOVEMENT DISORDERS Neuropathology of Parkinson’s disease • nigro-striatal pathway degeneration • leading to a depletion of striatal dopamine • some degeneration of other dopamine pathways too

39. Human midbrain Normal Parkinson’sdisease

40. Nigrostriatal (DA) and striatonigral (GABA) tracts X dopaminergic GABAergic

41. Pope John Paul II Janet Reno Katherine Hepburn Michael J. Fox Muhammad Ali Parkinson’s disease Pathophysiology: Primary: - loss of nigrostriatal DA projection

42. Parkinson’s disease Motoric • Tremor (~4-5 Hz, resting) • Bradykinesia • Rigidity • Loss of postural reflexes Depression Dementia Symptoms

43. Huntington’s disease • Pathophysiology • Atrophy of striatum • Loss of striatal GABA-ergic,medium spiny neurons Huntington’s Normal

44. Parkinson's disease - involves major loss of dopaminergic cells in the substantia nigra; Huntington's disease -involves massive loss of medium spiny neurons in the striatum. The symptoms of the two diseases are virtually opposite: Parkinson's disease is characterized by gradual loss of the ability to initiate movement, whereas Huntington's disease is characterized by an inability to prevent parts of the body from moving unintentionally.

45. Thank you for your attention!