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Download biol455 comparitive neurobiology lecture#21
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BIOL455 COMPARITIVE NEUROBIOLOGY LECTURE#21: CEREBELLUM! DR. OLLIE HULME! FALL 2010 ! UBC Housekeeping! [email protected]! [email protected]! Answer key + sample questions (inserted into slides) are now up on website office hours (Fri 1.30-4.30) www.hyooom.com! Neuroanatomy from lecture 9 is recommended for helping to understand all sensory, motor and cognitive topics, but will not be explicitly tested Overview of motor system! Cerebellum modulates upper motor system Upper controls lower Projects to all upper motor circuits, but no direct connections with lower Cerebellum = little-brain! Fundamental role is motor error reduction How? Three cerebellar components! Cerebellar peduncles Cerebellar Cortex Deep cerebellar nuclei Cerebellar cortex! Divided on basis of source of input [Flattened for diagram] Cerebrocerebellum! Indirect input from most of cortex Highly prominent in humans For highly skilled spatial + temporal sequences of movements Spinocerebellum! Input directly from spinal cord Midline – proximal muscles Lateral – distal muscles Crude somatotopy Vestibulocerebellum! Input directly from vestibular nuclei of brain stem Regulation of movements underlying posture + reflexes e.g vestibular occular reflex Connections to + from cerebellum! 3 major pathways connect cerebellum to rest of brain via peduncles efferent afferent both Saggital view! Input into cerebellum! Copies of Motor commands Sensory feedback from movement Cortical input to cerebellum! Frontal + Parietal cortex Input pathways! Cortex input is indirect via pontine nuclei Sensory input is indirect via brain stem nuclei e.g Inferior olive Somatotopy in spinocerebellum! Fractured map rather than continuous Output from cerebellar! Up to motor cortices Output is onto the upper motor system Down to brain stem nuclei Output to cortex! Closed loops – back to original cortical source [not necessarily motor regions] Open loops – output funneled back only to motor or premotor Output to brainstem nuclei! Output to brainstem nuclei! So what?! So input comes in. Output goes out. What is the cerebellum doing in between? Destination of input! Purkinje cell Motor error signal! Sensory feedback regarding what motor action actually happened Sensory information Inferior olive Information about what motor action was sent Motor Cortex Pontine nucleus Motor error correction! Comparison between motor command and sensory consequences of action allow motor error signal to be computed Sent back to upper motor system for correction Neuronal activity during movement! Saccade modification! Saccade modification! Patch moved to right eye Multiple movements to correct for weakness to begin with After 5 days corrective eye movements dissappear This error correction does not occur if cerebellum is damaged Vestibular Ocular Reflex! Vestibular system detects head movement And moves eyes in opposite direction to keep image stable on retina Disturb VOR with glasses! Intact cerebellum essential for correcting disturbance Damage from chronic alcohol abuse! Spinocerebellum damage causes inappropriate operation of muscle groups that rely on sensory feedback for smooth action Cerebellar gait! Because of somatotopy within cerebellum, walking is disturbed but speech + arm movement normal Cerebellar ataxia! Lack of motor co-ordination specific to body part controlled by damaged cerebellum Sample questions! Essay: 1. What is the function of the cerebellum and how does it implement this function? 2. What is the role of the cerebellum in motor learning? Multiple choice: Cerebellar ataxia is a disturbance in… motor coordination Cortical input to the cerebellum is mainly from… frontal and parietal cortices Cerebellum connects to the rest of the brain via… peduncles Next lecture! Visceral motor system chapter 21
