Overall organization of neural structures that control movementQuestions① What are the functions of the cerebellum in movement control?② What is the role of cerebellum in the control of locomotion?③ What is the role of basal ganglia in the control of movement?CEREBELLUMLarger than you’d thinkCerebellum• Modifies the activity pattern of upper motor neurons from the cerebral cortex• Primary roles: movement coordination and error detection Movement corrections mediated by cerebellum occurs during ongoing movement Movement error is stored as a form of motor learning (e.g. locomotor adaptation)A cerebellar Purkinje neuron in a living slice from mouse cerebellumActivity of Purkinje cells in two different statestonic activityWrist movementPurkinje cell less activeNeuronal activity in the cerebellum changes continually during the course of a movementDysdiadochokinesia: inability to make rapid alternating movementshttps://www.youtube.com/watch?v=4kEgOlHtMdQQuestions① What are the functions of the cerebellum in movement control?② What is the role of cerebellum in the control of locomotion?③ What is the role of basal ganglia in the control of movement?Cerebellum and locomotionCerebellum is involved with fine tuning of limb movements • Cerebellum receives sensory information through spinocerebellar pathways leg proprioceptors (mechanical state of limbs/stepping) interneurons in the CPG (state of spinal locomotor network)• Cerebellum also receives input from motor cortex and other regions (collaterals of corticospinal tract neurons)• Cerebellum compares actual leg movement with intended movement (from CPG and motor cortex) If error is detected, cerebellum sends corretive signals to brainstemCerebellum and locomotionDamage to the cerebellum• Disrupts modulation and coordination of ongoing movement difficulty producing smooth, well-coordinated, multi-joint movmements jerky and imprecise movement• Cerebellar ataxia: widened base of support, impaired coordination of joints, abnormal coupling between limbs during stepping • Cerebellum is involved in regulating stepping movementshttp://www.youtube.com/watch?v=kAiIfulpYzUQuestions① What are the functions of the cerebellum in movement control?② What is the role of cerebellum in the control of locomotion?③ What is the role of basal ganglia in the control of movement?Basal GangliaSet of nuclei deep within the cerebral hemispheresBasal Ganglia•Array of complex inhibitory and excitatory connections – impacts entire motor system (also control of eye movements)•Neuronal activity modulates upper motor neuron activity in anticipation of and during movements•Damage to basal ganglia cause inability to switch smoothly between commands (movement initiation and movement terminationFigure 18.10 Neurological diseases provide insights into function of the basal gangliaDegeneration substantia nigra(pigmented area)Size of corpus striatum is reducedDiseases of the basal ganglia• Parkinson’s: hypokinetic origin unclear too much inhibition rigidity, tremor, bradykinesia, postural instability• Huntington’s: hyperkinetic lack of inhibition genetic changes - mutant gene Chromosome 4; rapid, jerky motions: Choreiform mood, character affected
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