Presentation on theme: "Lecture 15: Cerebellum The cerebellum consists of two hemispheres and a medial area called the vermis. The cerebellum is connected to other neural structures."— Presentation transcript:
1Lecture 15:CerebellumThe cerebellum consists of two hemispheres and a medial area called the vermis. The cerebellum is connected to other neural structures by three pairs of peduncles. The figure shows a dorsal view of the cerebellum, and the peduncles and cerebellar nuclei are obscured (shown by black areas).VermisHemispherePedunclesDentate nucleusInterposed nucleus (emboliform and globose nuclei)Fastigial nuclei
2Cerebellar LobesPrimary fissureAnterior lobePosterior lobePosteriorlateral fissureFlocculonodular lobeNodulusFlocculusThe cerebellum is divided into three lobes: the anterior lobe, the posterior lobe, and the flocculonodular lobe.
4Neurons of the Cerebellum Output (to cerebellar nuclei and then to thalamus, brain stem, and vestibular nuclei)White matterMolecular layerPurkinje cell layerGranular layerBasket cellGranule cellClimbing fiberMossy fiberGolgi cellStellate cellThe cerebellar cortex consists of three layers and five types of neurons. Inputs to the cerebellum are carried by mossy fibers (from the inferior olive) and by climbing fibers (from pontine nuclei, the vestibular system, and the spinal cord). The only output system of the cerebellum is the axons of Purkinje cells.
6A GlomerulumMossy fiberGolgi cell axonGranule cell dendritesRosetteA single glomerulum consists of an incoming mossy fiber, clusters of small dendrites (called rosettes) from a few dozen granule cells, and the axons of the Golgi cells.
7Inputs Into the Cerebellum Mossy fibers (spinocerebellar tract and brain stem nuclei)Granule cellsClimbing fibers (inferior olive)Purkinje cellsExcitatory inputs to the cerebellum are provided by mossy fibers and climbing fibers. The mossy fibers originate in the spinocerebellar tract and in brain stem nuclei; they excite granule cells. The climbing fibers originate in the medulla (the inferior olive); they make synapses on Purkinje cells.
8Simple and Complex Spikes Simple spikeComplex spikeIn response to a single excitatory stimulus, a Purkinje cell may generatea single action potential (a simple spike, in response to mossy fiber input), ora larger action potential, followed by a few smaller action potentials (a complex spike, in response to a signal from climbing fibers).
9Wiring of the Cerebellum Stellate cells make inhibitory synapses on the dendrites of Purkinje cells. Parallel fibers activate Purkinje cells, basket cells, stellate cells, and Golgi cells. Basket cells inhibit relatively distant Purkinje cells. Golgi cells inhibit granular cells, decreasing their response to mossy fibers.GlomeruliParallel fibersGolgi cellsBasket cellsPurkinje cellsDistant Purkinje cellsStellate cellsGranular cellsMossy fibersClimbing fiber
10Neuronal Population Vectors of the Purkinje Cells and Neurons in the Cerebellar Nuclei
11Cerebellar Memory?If an action potential in a climbing fiber and another action potential in a parallel fiber arrive simultaneously at a Purkinje cell, the cell may “remember” thisevent with the help of a chemical mechanism, changing the synaptic efficacy.Climbing fibersParallel fibersPurkinje cell