2014/4/11 General View of Cerebellum 10 % total volume of the brain, but >50% of all its neurons The Cerebellum Provided with extensive information (40 times more axons project into the cerebellum than exit from it) Not necessary to basic elements of perception or movement. 陽明大學醫學院 腦科所 Damage to the cerebellum disrupts the spatial accuracy 陳昌明 副教授 and temporal coordination of movement. It impairs balance and reduces muscle tone and motor learning and certain cognitive functions. Position Lies above and behind the medullar and pons and occupies posterior cranial fossa Cerebellum Cerebellum external configuration • Located in posterior cranial fossa • Tentorium cerebelli (cerebrum), 4th ventricle (brain stem) • Communicate with other structure via •superior, middle, and inferior cerebellar peduncle 1 2014/4/11 External features External features Consists of two cerebellar hemisphere united in the Three peduncles midline by the vermis Inferior cerebellar peduncle 下小腦脚 －connect with medulla and with spinal cord, contain both afferent and efferent fibers Middle cerebellar peduncle 中小腦脚－connect with pons, contain afferent fibers Superior cerebellar peduncle 上小腦脚－connect with midbrain, contain mostly efferent fibers Cerebellum Lobes Anterior lobe corpus of Primary fissure cerebellar Longitudinal division Posterior lobe Vermis, Paravermal Region, Cerebellar Hemisphere Transverse division Flocculonodular lobe Anterior Lobe Posterolateral fissure Posterior Lobe Flocculonodular Lobe Lobes External features Superior surface Two deep fissures Primary fissure Tonsil of cerebellum 小腦扁桃体 two elevated Posterosuperior fissure masses on inferior Three lobs surface of hemispheral Flocculonodular lobe 絨球小結葉 portion just nearby flocculus and nodule foramen magnum Anterior lobe Corpus of cerebellar Posterior lobe Tonsil View from below 2 2014/4/11 External features Cerebellum & Brainstem, Inferior Surface, Anterior View Internal structures Deep Nuclei Gray matter Cerebellar cortex Cerebellar nuclei Dentate nucleus 齒狀核 1. fastigial Fastigial nucleus 頂核 nucleus Interposed nucleus 中間核 2. globose Emboliform nucleus 栓狀核 nucleus Globose nucleus球狀核 3. emboliform White matter－medullary nucleus center 髓体 4. dentate nucleus Internal structures Cerebellar cortex Fastigial nucleus Globose nucleus Dentate nucleus Emboliform nucleus medullary center 3 2014/4/11 1. Purkinje cell 2. granule cell 3. basket cell 4. Golgi cell 5. stellate cell 6. climbing fiber 7. mossy fiber 8. parallel fiber 9. inferior olivary nucleus 10. deep cerebellar nuclei Neurons in the cerebellar cortex are organized Cerebellar Cortex into three layers Inputs Climbing fibers •from Inferior olive Mossy fibers Output Purkinje neurons Interneurons Granule neurons Stellate neurons Basket neurons Molecular Golgi neurons Purkinje Granular NTA Fig. 13-11 The Purkinje Cells Receive Excitatory Input From Two Geometrical Plan of Afferent Fiber Parallel and Systems and Are Climbing fibers Inhibited by Three Local Interneurons 4 2014/4/11 Mossy and Climbing Fibers Encode Peripheral Climbing Fiber Activity Produces Long-Lasting and Descending Information Differently Effects on the Synaptic Efficacy of Parallel Fiber Simple and complex spikes recorded intracellularly from Purkinje cells Complex spikes (right bracket) are evoked by climbing fiber synapses, while simple spikes (left bracket) are produced by mossy fiber input. Cerebellum ：Internal Configurations Cerebellar Cortex Molecular Layer Stellate Cell --- taurine (inhibitory) afferent: parallel fiber efferent: Purkinje cell dendrite Basket Cell ---- GABA (inhibitory) afferent: parallel fiber efferent: Purkinje cell soma Parallel Fiber granule cell axon Purkinje Cell Dendrite Mossy fibers A mossy fiber is an axon terminal that ends in a large, bulbous swelling. Enter the granule cell layer and synapse on the dendrites of granule cells (right) In fact the granule cells reach out with little "claws" to grasp the terminals. The granule cells then send their axons up to the molecular layer, where they end in a T and run parallel to the surface, thus called parallel fibers. The parallel fibers synapse on the huge dendritic arrays of the Purkinje cells. 5 2014/4/11 Mossy fibers The climbing fiber Although each parallel fiber touches each It goes straight to the Purkinje cell layer and Purkinje cell only once, the thousands of parallel snake up the Purkinje dendrites, like ivy climbing fibers working together can drive the Purkinje a trellis. cells to fire like mad. Each climbing fiber associates with only one Purkinje cell, but when the climbing fiber fires, it provokes a large response in the Purkinje cell. Cerebellar cortex Cerebellum: Internal Configurations Cerebellar Cortex Purkinje Cell Layer interneurons All are inhibitory interneurons. Purkinje Cell The Golgi cell is found among the granule cells. -- 15,000,000 in number The stellate and basket cells live in the molecular layer. -- GABA (inhibitory) The basket cell (right) drops axon branches down into afferent from: parallel fiber the Purkinje cell layer where the branches wrap around climbing fiber the cell bodies like baskets. stellate cell basket cell efferent to: deep cortical nuclei Bergman’s glial cell 6 2014/4/11 Cerebellum: Internal Configurations Cerebellar Cortex Granular Layer Granular Cell -- 50,000,000,000 in number -- glutamic acid (excitatory) afferent: mossy fiber efferent: Purkinje cell dendrite basket cell, stellate cell Golgi cell Golgi Cell -- GABA (inhibitory) afferent: parallel fiber, mossy fiber rosette efferent: granule cell dendrite Cerebellum: Internal Configurations Neurons in the Cerebellar Cortex Synaptic Glomerulus Afferent terminals on granular layer Mossy Fiber Rosette -- afferent fibers except inferior olivary input -- 2/3 of medullary center Granular Cell Dendrite A glomerulus is a -- main afferent input clear space where the bulbous terminal of a Golgi Cell Axon mossy fiber makes -- synapse on granule cell dendrite synaptic contact with -- GABA (inhibitory) Golgi and granule cells. - Surrounded by Astrocyte Foot Process Synaptic Glomerulus Cerebellum Classifications Classification by Phylogenetic and Ontogenic Development Archicerebellum Paleocerebllum Neocerebellum Classification by Afferent Connection Vestibulocerebellum Spinocerebellum Pontocerebellum Classification by Efferent Connection Vermis Paravermal Region Cerebellar Hemisphere 7 2014/4/11 Archicerebellum (nodulus) Spinocerebellum Archicerebellum (flocculus) Pontocerebellum Paleocerebellum Neocerebellum Vestibulocerebellum Cerebellum Connections Cerebellum Connections Afferent Connections (2): Afferent Connections (1): 2. Middle Cerebellar Peduncle 1. Inferior Cerebellar Peduncle Pontocerebellar fiber Restiform Body Corticopontocerebellar Fiber Posterior Spinocerebellar Tract Reticulocerebellar Fiber Olivocerebellar tract 3. Superior Cerebellar Peduncle Cuneocerebellar Tract Anterior Spinocerebellar Tract Reticulocerebellar Tract Cerulocerebellar fiber Juxtarestiform Body Raphecerebellar fiber Vestibulocerebellar Tract Rubrocerebellar fiber Primary Vestibular Fiber Hypothalamocerebellar fiber Cerebellum Connections Three functional divisions Efferent Connections : Vestibulocerebellum 1. Superior Cerebellar Peduncle 前庭小腦 Archicerebellum 原小腦 Cerebellothalamic fiber Flocculonodular lobe Intermediate zone Intermediate Vermis - from 3 deep nuclei to VPLo, VLc, CL Spinocerebellum zone Lateral 脊髓小腦 Cerebellorubral fiber Paleocerebellum 舊小腦 - from nucleus interpositus & dentate nucleus Vermis and Ascending portion of uncinate fasciculus of Russell intermediate zone 2. Inferior Cerebellar Peduncle Cerebrocerebellum 大腦小腦 Flocculonodular lobe Fastigiovestibular fiber Neocerebellum 新小腦 Descending portion of uncinate fasciculus of Russell Lateral zone 8 2014/4/11 Functional divisions of cerebellar cortex The Cerebellum Has Three Functionally Distinct Regions The Three Functionally Distinct Regions Cerebellar divisions Have different inputs and outputs Spinocerebellum: Vermis Spinocerebellum Intermediate hem. (Vermis + Intermed. Hem) Cerebrocerebellum: Lateral hem. Control of limbs and trunk Cerebrocerebellum (Lateral hemisphere) Planning of movement+ Vermis IVth vent Vestibulo-cerebellum Intermediate hem. (Floculo-nodular lobe) Lateral hem. Control of eye & head movements Balance NTA Fig. 13-1 Floculo-nodular lobe Connections and function of cerebellum Vestibulo-cerebellum Vestibulocerebellum Connections Input: Afferents: receive input from vestibular nuclei and vestibular primary vestibular nuclei Efferents: projects to the vestibular nucleus → Output: (1) vestibulospinal tract → motor neurons of anterior horn vestibular for reflexively control of equilibrium nuclei (2) vestibulo-ocular tract → medial longitudinal fasciculus → CN nucleus 3, 4, 6 for EOM control. Function: involved in eye movements and maintain balance 9 2014/4/11 Main Connections of the Vestibulocerebellum Vestibular Organ Floculonodular Lobe BILATERAL VESTIBULAR NUCLEUS Vestibulospinal Tract MLF FASTIGIAL NUCLEUS Lower motor neuron ARCHICEREBELLUM LMN Spinocerebellum (vermis & intermediate) Spinocerebellum Input: periphery and spinal cord Output: cortex Afferents: Spinocerebellar tracts The Ventral and dorsal spinocerebellar End mainly in the anterior lobe, the paramedian lobule, and the pyramis of the posterior lobe tracts 10 2014/4/11 The efferents Connections and Function of Neo- cerebellum Vermis projects to the fastigial nucleus → vestibular nuclei and