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Lecture 18

Lecture 18 - Basal Ganglia & Cerebellum

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University of Toronto St. George
Michelle French

L18 Oct 24 2011Basal GangliaCerebellumNot directly involved in programming apparatus of motor systemBasal GangliaRegulates flow of volitional drive internal will to initate a movement to premotor centers2 tiers of nuclei collectively known as striatumpallidumstriatum topographic input specific directing from entire cerebral cortexthal centromedian nucleuswhere spinoreticulothalamic system terminatesso has brainstem motor input ex postural locomotorpallidum projects to premotor centersstriatum normally quiet exact opposite of located deep within hemispherespallidumhigh bg activity 4050 set of neuronal nucleiimpulsessecondfront sectionwhen striatum receives sufficient stimulatn from basal ganglia deep cortex or thal activates burst of act potsinside surrounding inhibit specific pallidum neuronssilenced while thalstriatum activeduring disinhibit specific in wall of lateral Central Pattern Generators in motor centresventriclestriatum intiate motor program coordinatnbroken into nuc by looks like backwards way of intiating action bands of white matterbut preferredpallidum inside also in dopamine released by substantia nigra blacken w substantia nigra only age since dopamine breaks down neurons project pale part split apart to striatumby band of white facilitating activation of striatal cells at matter but fns samespecific locations important in learning dark part of substantia mechs strengthen synaptic connections in nigraacts on striatal cellslearn to recognize specific cues pallidum can choose when appropriate to initiate subthalamic n acts on given motor act must use a lot of cuesstriatumanalyze a lot of infomodulatoryPallidumStriatal modulationNeurons are tonically discharging constant Substantia nigra SN neurons containing background activitydopamine facilitate striatopallidal projection inhibit premotor thalamus esp supplementary neuronsmotor area in medial wallvolitnal s colliculus striatum chooses motor act to perform at any eye head movements gazesteering instant guided by corticalreticular inputsmesencephalic locomotory region locomotnSN dopaminergic system plays a key role in Fn tonically suppresses motor programsdetermining active part of striatumAs soon as inhibitn removedtoo much Facilitate direct pathway of projectn from excitatnstriatum to pallidumin order to initiate a specific movement a specific premotor center is disinhibitedPremotor disinhibitionAccomplished by inhibiting pallidal neuronsstriatum projects to palliduminhibits pallidal neurons using GABA also used by pallidal cells on premotor centres very common inhibitorytherefore activation of a specific locus in striatum can enable a motor program by removing the tonic inhibition of itParkinsons Disease
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