Download to read offline
More Related Content
Similar to basal ganglia-1 neurology critical usg.pptx
basal ganglia-1 neurology critical usg.pptx
- 1. BASAL GANGLIA AND CONNECTIONS DrShamir SR, Neurology
- 2.
- 3.
- 4. Basal nuclei Clinical neuroanatomyby Snells 8th edition
- 5. Clinical neuroanatomy bySnells 8th edition
- 6. Cadaveric section ofbasal ganglia and its relations Clinical neuroanatomy by Snells 8th edition
- 7. Axial view atthe level of basal ganglia Netters concise anatomy
- 8. Structures of BasalGanglia
- 9. Structures of BasalGanglia
- 11. Basal Ganglia- components 1.Neostriatum Caudate nucleus Putamen 2. Paleostriatum Globus pallidus external segment (GPe) Globus pallidus internal segment (GPi) 3. Substantia Nigra Pars compacta (SNc) Pars reticulata (SNr) 4. Subthalamic nucleus (STN)
- 12. Basal ganglia components Dejong, the neurological examination 8th edition
- 13. CAUDATE NUCLEUS Lies deep inthe substance of the cerebral hemisphere Between lateral ventricle and insula Head, body and tail Separated from thalamus by sulcus terminalis groove Henley, C.
- 14. Caudate Nucleus C shapedture (“tail”) Lateral wall of lateral ventricle
- 15. Coronal view at head of caudate Nettersconcise anatomy
- 16. Coronal view ofbrain at the level of head of caudate
- 17. Coronal view atant limb of internal capsule Body of caudate Netters concise anatomy
- 18. Anterior limb ofinternal capsule- coronal view
- 19. Axial view ofbrain through midbrain -tail of caudate Netters concise anatomy
- 20. Axial view ofthe Brain through the midbrain
- 21. Putamen Click iconto add picture • Located lateral to GP • Separated from the insular cortex by extreme capsule, claustrum and external capsule • Functionally identical to caudate – together called as striatum Netters concise anatomy
- 22. Globus pallidus Clickicon to add picture • Medial to putamen, just lateral to the third ventricle • Separated from putamen by external medullary lamina • Divided into internal and external zone by internal medullary lamina • Use primarily GABA as a neurotransmitter • Contains 2 components – Gpi and Gpe • Paleness of GP is due to presence of high concentration of myelinated nerve fibres. Netters concise anatomy
- 23. Substantia nigra Netters conciseanatomy Click icon to add picture • Lies in the cerebral peduncle between the crus cerebri and the tegmentum of the midbrain at the level of the superior colliculi. • Divided in to pars reticulata(GABA - SNr) and pars compacta(Dopamine- SNc) • Neuromelanin (makes the structure dark) and it is present in SNc
- 24. Clinical neuroanatomy bySnells 8th edition
- 26. Subthalamic nucleus • -Lies below the thalamus • - Lies above the substantia nigra • - output is excitatory in nature (GLUTAMINERGIC) • - Best surgical target for electrode placement during deep brain stimulation (STN-DBS)
- 27. Claustrum Click icon toadd picture Thin sheet of gray matter that is separated from lateral surface of lentiform nucleus by external capsule. Function : unknown Netters concise anatomy
- 28. Categorization of nuclei •Input nuclei – Striatum(Caudate nucleus and Putamen) , sub thalamic nucleus • Output nuclei – Globus pallidus interna(Gpi), Substania nigra pars reticulata(SNr) • Intrinsic nuclei – Globus pallidus externa(Gpe) and Substania nigra pars compacta(SNc)
- 29.
- 30.
- 31. Excitatory vs Inhibitory •CORTEX • THALAMUS EXCITATORY • STN • STRIATUM INHIBITORY • PALLIDUM
- 32. Dejong , theneurological examination 8th edition
- 33. Clinical neuroanatomy bySnells 8th edition
- 34. Principle connections ofbasal ganglia Clinical neuroanatomy by Snells 8th edition
- 35. Connections of basalganglia to thalamus Clinical neuroanatomy by Snells 8th edition
- 36. Basal ganglia Afferents •Afferents: • Cerebral cortex to caudate and putamen ( largest –sensory motor cortex) • Substantia nigra pars compacta to putamen and caudate • Subthalamic nucleus to globus pallidus and to substantia nigra pars reticulata • Centromedial nucleus of the thalamus to putamen and caudate • Raphe magnus nucleus to putamen and caudate
- 37. Basal ganglia Efferents •Efferents: • Putamen and caudate to globus pallidus • Putamen and caudate to substantia nigra pars reticularis • Globus pallidus to subthalmic nucleus • Globus pallidus to ventroanterior and ventrolateral nuclei of the thalamus
- 38. Neurons of BasalGanglia • Medium Spiny Neurons(90%) • Interneurons(10%)
- 39. Neurons of thebasal ganglia
- 40. Neurotransmitters • Glutamate alwaysexcitatory • GABA always inhibitory • Dopamine can be excitatory or inhibitory depending on the receptor. 1. Excitatory to D1 receptor - stimulates adenylate cyclase 2. Inhibitory to D2 receptor – inhibits adenylate cyclase • Spiny Neurons of caudate contain – Gaba, encephalin and substanceP
- 41. Glutamate • Major excitatoryneurotransmitter in brain • Present in over ½ of total neurons in CNS • Examples • Thalamocortical projections • Cortico - striate projections • Subthalamic nucleus projection to outflow nucleus (in indirect pathway)
- 42. GABA - GammaAmino Butyric Acid • GABA is an inhibitory mediator in the brain • Acts by increasing chloride conductance Glutamate GABA GAD - Glutamic Acid Decarboxylase
- 43. Pathways of BasalGanglia • Direct pathway – mediated by D1 dopamine receptors and results in a faciltation of movement • Indirect pathway – mediated by D2 receptors and results in an inhibition of movement • Hyperdirect pathway – Bypasses Striatum
- 44. Direct and Indirectpathways
- 46.
- 47. Clinical neuroanatomy bySnells 8th edition
- 48. Functions of BasalGanglia • Motor loop- control voluntary movement and motor skills • Prefrontal loop – associative loop • Limbic loop- involved with the motor expressions of emotions • Cognitive loop- important in learning new motor tasks • Oculomotor loop- control of saccadic eye movements • Other functions – attention and time estimation, implicit learning, habit formation, and reward related behaviour
- 50. • Output nucleihave tonically inhibitory discharges • The connection of striatum receiving strongest input from cortex will send strong inhibitory signal to output nuclei . • The connection receiving strong input from striatum will be inhibited and its inhibitory signal to thalamus will be disinhibited leading to its selection.
- 51. • The combination offocused inhibition from the striatum with the more diffuse excitation from the subthalamus would both decrease the activity in selected channels and increase activity in non-selected channels in the basal ganglia output nuclei
- 52. • Transmission in recentlyactive (selected) channel(s) is reinforced by the combined phasic release of dopamine and glutamate evoked by an unpredicted biologically salient sensory event (eg, reward). • Nonactive channels lack the eligibility trace required for dopamine reinforcement at the synapse.
- 53. • Selection bythe basal ganglia is determined in part by the relative strength of inputs to the striatum (the common currency), • Reward-related modulation of afferent signals would effectively bias selection to favor reward-related inputs.
- 54. Basal ganglia loops– motor and non-motor Motor loop Prefrontal loop (Associative) Limbic loop
- 55. Basal Ganglia (OculomotorLoop) Connections Frontal Eye Field (area 8) THALAMUS ( VA, DM) STRIATUM (Caudate Nucleus) SNr (Substantia Nigra, pars reticulata) Sup Colliculus
- 56. So what ifhappens if selection system fails ? • Selection failure – parkinsons disease • Soft selection – Schizophrenia • Hard selection – Obsessive compulsive disorders and addictions
- 57. • A –selected channel undergoes disinhibition and non selected are inhibited • B – selected channel is also inhibited – no desired action occur • C- unwanted channels are not properly inhibited – so interruption between desired and undesired actions occur • D – desired channel is excessively disinhibited – so person will have excess activity or thought of the desired action
- 58. Summary 1. Modulating actionthrough disinhibition 2. Direct and Indirect Pathways Direct pathway facilitates action Indirect pathway suppresses action 3. Principle of selection – to do a desired task 4. Reinforcement learning through reward and punishment systems
- 59. Thalamus Clinical neuroanatomy bySnells 8th edition
- 61. Relations of thalamus Clinicalneuroanatomy by Snells 8th edition
- 62. RELATIONS OF THALAMMUS Clinicalneuroanatomy by Snells 8th edition
- 63. Thalamic nuclei • 5major functional classes: • reticular and intralaminar nuclei - arousal and nociception; • sensory nuclei • effector nuclei -motor function and aspects of language • associative nuclei - cognitive functions • limbic nuclei concerned with mood and motivation.
- 68. • Vascular lesions destroythese nuclei in different combinations and produce sensorimotor and behavioral syndromes depending on which nuclei are involved. • Tuberothalamic territory strokes produce impairments of arousal and orientation, learning and memory, personality, and executive function; superimposition of temporally unrelated information; and emotional facial paresis. • Paramedian infarcts cause decreased arousal, particularly if the lesion is bilateral, and impaired learning and memory. • Autobiographical memory impairment and executive failure result from lesions in either of these vascular territories.
- 69. • Language deficits resultfrom left paramedian lesions and from left tuberothalamic lesions that include the ventrolateral nucleus. • Right thalamic lesions in both these vascular territories produce visual-spatial deficits, including hemispatial neglect. • Inferolateral territory strokes produce contralateral hemisensory loss, hemiparesis and hemiataxia, and pain syndromes that are more common after right thalamic lesions. • Posterior choroidal lesions result in visual field deficits, variable sensory loss, weakness, dystonia, tremors, and occasionally amnesia
- 70. Major thalamic vascularterritories (1) TUBEROTHALAMIC, (2) INFEROLATERAL, (3) PARAMEDIAN, (4) POSTERIOR CHOROIDAL VESSELS
- 71.
- 72.
- 73.
- 74.
- 75.
- 78.
- 80.
- 81. DISORDERS SITE OFLESION CHOREA Caudate ATHETOSIS Globus pallidus BALLISM Subthalamic nucleus, indirect pathway affected PARKINSON DISEASE Degeneration of neurons of substantia nigra , hypersenstivity of dopamine receptors within corpus striatum. decreased direct pathway, increased indirect pathway HUNTINGTON Gaba,sub P, ACH secreting neurons of striatonigral inhbiting pathway degenerate. Dopamine secreting neurons of substantia nigra become over active, thus nigrostriatal pathway inhibits caudate nucleus and putamen. Indirect pathway
- 84. References • DEJONG’S;THE NEUROLOGICALEXAMINATION,7THEDITION;399-409 • NETTER’S CONCISE NEUROANATOMY • SNELLS CLINICAL NEUROANAT OMY 8TH EDITION
- 85.
Editor's Notes
- #38 Direct- substance P and dynorphin , Indirect - enkephalin
- #40 Substance P uses d1 and encephalin uses D2
- #58 Acetylcholine Suppresses action through both pathways Decrease firing in response to reward directed cues BG Role in Action Selection Selection through direct pathway; surround suppression through indirect pathway