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Encyclopedia > Dentate nucleus
Figure 1a: A human brain, with the cerebellum in purple.
Figure 1a: A human brain, with the cerebellum in purple.
For assistance with anatomical location terms, see anatomical terms of location.

The cerebellum (Latin: "little brain") is a region of the brain that plays an important role in the integration of sensory perception and motor output. Many neural pathways link the cerebellum with the motor cortex—which sends information to the muscles causing them to move—and the spinocerebellar tract—which provides feedback on the position of the body in space (proprioception). The cerebellum integrates these two functions, using the constant feedback on body position to fine-tune motor movements. Image File history File links Human brain with the cerebellum highlighted in purple. ... Image File history File links Human brain with the cerebellum highlighted in purple. ... The human brain is the center of the central nervous system in humans and the primary control center for the peripheral nervous system. ... In human and zoological anatomy (sometimes called zootomy), several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... Latin is the language originally spoken in the region around Rome called Latium. ... In the anatomy of animals, the brain, or encephalon, is the supervisory center of the nervous system. ... PSYCHOLOGY In psychology and the cognitive sciences, perception is the process of acquiring, interpreting, selecting, and organizing sensory information. ... A motor is a device that converts energy into mechanical power, and is often synonymous with engine. ... A neural pathway is a neural tract connecting one part of the nervous system with another, usually consisting of bundles of elongated, myelin insultated neurons, known collectively as white matter. ... // Early work on motor cortex function Back in the 1940s, Canadian neurosurgeon Wilder Penfield wanted to know which bits of epileptics brains he could suck out without them noticing. ... A top-down view of skeletal muscle Muscle is a contractile form of tissue. ... The spinocerebellar tract is a set of axonal fibers originating in the spinal cord and terminating in the cerebellum. ... Proprioception (from Latin proprius, meaning ones own and perception) is the sense of the position of parts of the body, relative to other neighbouring parts of the body. ...


Because of this 'updating' function of the cerebellum, lesions within it are not so debilitating as to cause paralysis, but rather present as feedback deficits resulting in disorders in fine movement, equilibrium, posture, and motor learning. Initial observations by physiologists during the 18th century indicated that patients with cerebellar damage show problems with motor coordination and movement. Research into cerebellar function during the early to mid 19th century was done via lesion and ablation studies in animals. Research physiologists noted that such lesions led to animals with strange movements, awkward gait, and muscular weakness. These observations and studies led to the conclusion that the cerebellum was a motor control structure[1] . However modern research has shown that the cerebellum has a broader role in a number of key cognitive functions, including attention and the processing of language, music, and other sensory temporal stimuli. A lesion is a non-specific term referring to abnormal tissue in the body. ... Paralysis is the complete loss of muscle function for one or more muscle groups. ... Motor learning is the process of improving the smoothness and accuracy of movements. ... Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ... Look up Attention on Wiktionary, the free dictionary Attention is the cognitive process of selectively concentrating on one thing while ignoring other things. ...

Figure 1b: MRI image showing a mid-sagittal view of the human brain, with the cerebellum in purple.
Figure 1b: MRI image showing a mid-sagittal view of the human brain, with the cerebellum in purple.

Contents

Image File history File links Deskulled sagittal MRI with cerebllum highlighted in purple. ... Image File history File links Deskulled sagittal MRI with cerebllum highlighted in purple. ... Magnetic resonance imaging (MRI) - also called magnetic resonance tomography (MRT) - is a method of creating images of the inside of opaque organs in living organisms as well as detecting the amount of bound water in geological structures. ...


General features

The cerebellum is located in the inferior posterior portion of the head (the hindbrain), directly dorsal to the brainstem and pons, inferior to the occipital lobe (Figs. 1 and 3). Because of its large number of tiny granule cells, the cerebellum contains nearly 80% of all neurons in the brain, although it constitutes only 10% of total brain volume. The cerebellum receives nearly 200 million input fibers; in contrast, the optic nerve is composed of a mere one million fibers. Hindbrain has been used to describe several structures found in the brains of vertebrates. ... The brain stem is the stalk of the brain below the cerebral hemispheres. ... The pons is a knob on the brain stem. ... The occipital lobes are the visual processing center of mammalian brains. ... In neuroscience, granule cells are tiny cells found within the granular layer of the cerebellum. ... Neurons (also spelled neurones or called nerve cells) are the primary cells of the nervous system. ... The optic nerve is the nerve that transmits visual information from the retina to the brain. ...


The cerebellum is divided into two large hemispheres, much like the cerebrum, and contains ten smaller lobules. The cytoarchitecture (cellular organization) of the cerebellum is highly uniform, with connections organized into a rough, three-dimensional array of perpendicular circuit elements. This organizational uniformity makes the nerve circuitry relatively easy to study. To envision this "perpendicular array", imagine a tree-lined street with wires running straight through the branches of one tree to the next. The term hemisphere is used in three different meanings: one-half of the Earth (or other planetary or stellar body; see also New World and Old World) Eastern Hemisphere and Western Hemisphere. ... For other articles about other subjects named brain see brain (disambiguation). ... Cytoarchitectonics represents the study of the microscopic, cellular composition of structures within the body. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, sometimes called the building blocks of life. ... Dimension (from Latin measured out) is, in essence, the number of degrees of freedom available for movement in a space. ... In computer programming, an array, also known as a vector or list, is one of the simplest data structures. ... In cognitive neuroscience, a neural network (also known as a neuronal network or biological neural network to distinguish from artificial neural networks) is a population of interconnected neurons. ...


Development and evolution

Figure 2: Drawing of the cells in the chicken cerebellum by S. Ramón y Cajal
Figure 2: Drawing of the cells in the chicken cerebellum by S. Ramón y Cajal

During the early stages of embryonic development, the brain starts to form in three distinct segments: the prosencephalon, mesencephalon, and rhombencephalon. The rhombencephalon is the most caudal (toward the tail) segment of the embryonic brain; it is from this segment that the cerebellum develops. Along the embryonic rhombencephalic segment develop eight swellings, called rhombomeres. The cerebellum arises from two rhombomeres located in the alar (dorsal, or upper) plate of the neural tube, a structure that eventually forms the brain. The specific rhombomeres from which the cerebellum forms are rhombomere 1 (Rh.1) caudally (near the tail) and the "isthmus" rostrally (near the front)[2] . Image File history File links Drawing of the cells of the chick cerebellum by Santiago Ramón y Cajal, from Estructura de los centros nerviosos de las aves, Madrid, 1905?. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Drawing of the cells of the chick cerebellum by Santiago Ramón y Cajal, from Estructura de los centros nerviosos de las aves, Madrid, 1905?. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, sometimes called the building blocks of life. ... Binomial name Gallus gallus (Linnaeus, 1758) A chicken (Gallus gallus) is a type of domesticated bird which is often raised as a type of poultry. ... Santiago Ramón y Cajal Santiago Ramón y Cajal (May 1, 1852–October 17/18, 1934) was a famous Spanish histologist and father of neuroscience. ... Embryos (and one tadpole) of the wrinkled frog (Rana rugosa). ... In the anatomy of vertebrates, the prosencephalon is a part of encephalon, or brain. ... In biological anatomy, the mesencephalon (or midbrain) is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals. ... Wikipedia does not have an article with this exact name. ... In the vertebrate embryo, a rhombomere is a segment of the developing rhombencephalon. ... The neural tube is the embryonal structure that gives rise to the brain and spinal cord. ...


The neural tube is organized so that the alar plate typically gives rise to structures involved in sensory functions; the basal (ventral, or lower) plate gives rise to motor functioning structures. Given its alar plate origins, the cerebellum would be expected to be devoted primarily to sensory functions. Despite its embryological origin, one of the many ironies of the cerebellum is that it functions primarily to modulate motor function.


Two primary regions are thought to give rise to the neurons that make up the cerebellum. The first region is the ventricular zone in the roof of the fourth ventricle. This area produces Purkinje cells and deep cerebellar nuclear neurons. These cells are the primary output neurons of the cerebellar cortex and cerebellum. The second germinal zone (cellular birthplace) is known as the external granular layer. This layer of cells—found on the exterior the cerebellum—produces the granule neurons. Once born, the granule neurons migrate from this exterior layer to form an inner layer known as the internal granule layer. The external granular layer ceases to exist in the mature cerebellum, leaving only granule cells in the internal granule layer. The cerebellar white matter may be a third germinal zone in the cerebellum; however its function as a germinal zone is controversial. The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. ... Drawing of pigeon Purkinje cells (A) by Santiago Ramon y Cajal Purkinje cells are a class of GABAergic neuron located in the cerebellar cortex. ... In neuroanatomy, a nucleus is a central nervous system structure that is composed mainly of gray matter, and which acts as a hub or transit point for electrical signals in a single neural subsystem. ... White matter is one of the two main solid components of the central nervous system. ...


The cerebellum is of archipalliar phylogenetic origin. The pallium is a term for gray matter that forms the cortex. The archipallium is the one of the most evolutionarily primitive brain regions. The circuits in the cerebellar cortex look similar across all classes of vertebrates, including fish, reptiles, birds, and mammals (e.g., Fig. 2). This has been taken as evidence that the cerebellum performs functions important to all vertebrate species. In anatomy of animals, the archipallium the oldest region of the brains pallium. ... In biology, Phylogenetics (Greek: phylon = race and genetic = birth) is the taxonomical classification of organisms based on how closely they are related in terms of evolutionary differences. ... In the anatomy of animals, the pallium is a part of the brain that is the evolutionary precedent of the cerebrum. ... Charles Darwin, father of the theory of evolution by natural selection. ... Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... Groups Conodonta Hyperoartia Petromyzontidae (lampreys) Pteraspidomorphi (early jawless fish) Thelodonti Anaspida Cephalaspidomorphi (early jawless fish) Galeaspida Pituriaspida Osteostraci Gnathostomata (jawed vertebrates) Placodermi Chondrichthyes (cartilaginous fish) Acanthodii Osteichthyes (bony fish) Actinopterygii (ray-finned fish) Sarcopterygii (lobe-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Tetrapoda Amphibia Amniota Sauropsida/(Reptiles) Aves (Birds) Synapsida Mammalia... hey ryan ... Orders  Crocodilia - Crocodilians scary crocodiles. ... For other meanings of bird, see bird (disambiguation). ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... In biology, the most commonly used definition of species was first coined by Ernst Mayr. ...


Anatomy

The cerebellum contains similar gray and white matter divisions as the cortex. Embedded within the white matter—which is known as the arbor vitae (Tree of Life) in the cerebellum due to its branched, treelike appearance—are four deep cerebellar nuclei. Three gross phylogenetic segments are largely grouped by general function. The three cortical layers contain various cellular types that often create various feedback and feedforward loops. Oxygenated blood is supplied by three arterial branches off the basilar and vertebral arteries. Grey matter is a category of nervous tissue with many nerve cell bodies and few myelinated axons. ... ... Species Thuja koraiensis Thuja occidentalis Thuja plicata Thuja standishii Thuja sutchuenensis Thuja (pronounced Thuya) is a genus of coniferous trees in the Cupressaceae (cypress family). ... The Tree-of-Life is a fictional plant (the ancestor of yams, with similar appearance and taste) in Larry Nivens Known Space universe, for which all Hominids have an in-built genetic craving. ... The coniferous Coast Redwood, the tallest tree species on earth A tree can be defined as a large, perennial, woody plant. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Red blood cells (erythrocytes) are present in the blood and help carry oxygen to the rest of the cells in the body Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). ... Section of an artery An artery or arterial is also a class of highway. ... The basilar artery is one of the arteries which the brain supplies with oxygen-rich blood. ... The vertebral arteries are branches of the subclavian arteries. ...


Divisions

Figure 3: Cerebellum and surrounding regions; sagittal view of one hemisphere. A: Midbrain. B: Pons. C: Medulla. D: Spinal cord. E: Fourth ventricle. F: Arbor vitae. G: Tonsil. H: Anterior lobe. I: Posterior lobe.
Figure 3: Cerebellum and surrounding regions; sagittal view of one hemisphere. A: Midbrain. B: Pons. C: Medulla. D: Spinal cord. E: Fourth ventricle. F: Arbor vitae. G: Tonsil. H: Anterior lobe. I: Posterior lobe.

There are three phylogenetic divisions within the cerebellum: the flocculonodular, anterior, and posterior lobes (Fig. 3). These divisions are also called the archicerebellum, paleocerebellum, and neocerebellum, respectively, terms that more clearly reflect the method of dividing the lobes by their evolutionary age. The archicerebellum represents the oldest evolutionary cerebellar structure, and the neocerebellum represents the most recently evolved region. These divisions are divided from the front to the back of the cerebellum; starting with the flocculonodular lobe in the front, and ending with the posterior lobe in the back. The anterior and posterior lobes are separated by the primary fissure. The posterior and flocculonodular lobes are separated by the posterolateral fissure (Fig. 4). Image File history File links Diagram of cerebellar regions. ... Image File history File links Diagram of cerebellar regions. ... In biological anatomy, the mesencephalon (or midbrain) is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals. ... The pons is a knob on the brain stem. ... The medulla oblongata is the lower portion of the brainstem. ... The spinal cord is a part of the vertebrate nervous system that is enclosed in and protected by the vertebral column (it passes through the spinal canal). ... The ventricular system is a fluid conducting system within the brain. ... The arbor vitae (Tree of Life) refers to the cerebellar white matter, so called for its branched, tree-like appearance. ...


The cerebellum can also be divided by function rather than evolutionary age. This results in three functional divisions that run perpendicular to the previously mentioned phylogenetic divisions. Rather than running from front to back, like the phylogenetic divisions, the functional regions align from the midline outwards toward the sides of the body. The midline division is called the medial zone, also known as the cerebellar vermis (“worm”) because of its long, slender shape; the vermis is further subdivided into smaller regions called lobules. The region just lateral (away from the center) of the vermis is called the intermediate zone; the most lateral, outer region is the lateral zone (Fig. 4). Part of the structure of animal brains, the cerebellar vermis is a narrow, wormlike structure between the hemispheres of the cerebellum. ... WORM means Write Once, Read Many. ... The term lateral can refer to: an anatomical definition of direction. ...


Much of what is understood about the functions of the cerebellum stems from careful documentation of the effects of focal lesions in human patients who have suffered from injury or disease or through animal lesion research.


Cerebellar structure and function from a phylogenetic perspective

Archicerebellum

The archicerebellum is associated with the flocculonodular lobe and is mainly involved in vestibular and eye movement functions. It receives input from the inferior and medial vestibular nuclei and sends fibers back to the vestibular nuclei, creating a feedback loop that allows for the constant maintenance of balance. Equilibrioception or sense of balance is one of the physiological senses. ... An eye is an organ that detects light. ...


Paleocerebellum

The paleocerebellum controls proprioception related to muscle tone (constant, partial muscle contraction that is important for the maintenance of posture). The paleocerebellum receives its inputs from the posterior and anterior spinocerebellar tracts, which carry information about the position and forces acting on the legs. The paleocerebellum then sends axonal projections to the deep cerebellar nuclei. Muscle tone is the continuous and passive partial contraction of the muscles. ... While not moving, a human can be in one of the following main positions. ... The spinocerebellar tract is a set of axonal fibers originating in the spinal cord and terminating in the cerebellum. ...


Neocerebellum

The neocerebellum receives input from the pontocerebellar tract and projects to the deep cerebellar nuclei. The pontocerebellar tract originates at the pontine nuclei, which receive their input from the cerebral motor cortex. Thus, the neocerebellum is associated with motor control, in particular, the coordination of fine finger movements such as those required by typing. The pontine nuclei are a part of the pons which store the memory of intention during motor activity. ...


The functional organization of the cerebellum

Figure 4: Schematic representation of the major anatomical subdivisions of the cerebellum. Superior view of an "unrolled" cerebellum, placing the vermis in one plane.
Figure 4: Schematic representation of the major anatomical subdivisions of the cerebellum. Superior view of an "unrolled" cerebellum, placing the vermis in one plane.

Image File history File links Download high resolution version (914x637, 66 KB)Schematic representation of the major anatomical divisions of the cerebellum. ... Image File history File links Download high resolution version (914x637, 66 KB)Schematic representation of the major anatomical divisions of the cerebellum. ...

Vermis

The vermis receives its inputs mainly from the spinocerebellar tracts from the trunk of the body. These tracts carry to the vermis information on the position and balance of the torso. The vermis sends projections to the fastigial nucleus of the cerebellum, which then sends output to the vestibular nuclei. The vestibular nuclei are structures important for the maintenance of balance.


Intermediate zone

The intermediate zone receives input from the corticopontocerebellar fibers that originate from the motor cortex. These fibers carry a duplicate of the information that was sent from the motor cortex to the spine in order to effect a movement. The intermediate zone also receives sensory feedback from the muscles. These two streams of information are integrated by this region, allowing for the feedback comparison of what the muscles are supposed to be doing with what they are actually doing.


Lateral zone

The lateral zone receives input from the parietal cortex via pontocerebellar mossy fibers regarding the location of the body in the world. The large numbers of feedback circuits allow for the integration of this body position information with indications of muscle position, strength, and speed. The parietal lobe is a lobe in the brain. ...


Deep nuclei

The four deep cerebellar nuclei are in the center of the cerebellum, embedded in the white matter. These nuclei receive inhibitory ( GABAergic) inputs from Purkinje cells in the cerebellar cortex and excitatory ( glutamatergic) inputs from mossy fiber pathways. All output fibers of the cerebellum originate from the these nuclei. Inhibitory Postsynaptic Potential is commonly abbreviated to Currently there is more information available under the heading synapse. ... Chemical structure of GABA Gamma-aminobutyric acid (GABA) is a neurotransmitter in widely divergent species. ... In neuroscience, an excitatory postsynaptic potential (EPSP) is a temporary increase in postsynaptic membrane potential caused by the flow of positively-charged ions into the postsynaptic cell. ... Glutamate is the anion of glutamic acid. ... Mossy fibers or mossy cells provide stimulation to inhibitory GABA interneurons in the hippocampus. ...


The four nuclei are known as the dentate, emboliform, globose, and fastigial. An easy mnemonic device to remember these names and positions relative to their position from the midline is the phrase "Don't Eat Greasy Food", where each letter indicates the lateral to medial location in the cerebellar white matter. The nonhuman analogue of the emboliform and globose nuclei is a single, fused nucleus interpositus (interposed nucleus). The vestibular nuclei in the brainstem are analogous structures to the deep nuclei, and receive inputs from the flocculonodular lobe of the cerebellum. A mnemonic (pronounced in American English, in British English) is a memory aid. ... The brain stem is the stalk of the brain below the cerebral hemispheres. ...


Cortical layers

Figure 5: Microcircuitry of the cerebellum. Excitatory synapses are denoted by (+) and inhibitory synapses by (-). MF: Mossy fiber. DCN: Deep cerebellar nuclei. IO: Inferior olive. CF: Climbing fiber. GC: Granule cell. PF: Parallel fiber. PC: Purkinje cell. GgC: Golgi cell. SC: Stellate cell. BC: Basket cell.
Figure 5: Microcircuitry of the cerebellum. Excitatory synapses are denoted by (+) and inhibitory synapses by (-). MF: Mossy fiber. DCN: Deep cerebellar nuclei. IO: Inferior olive. CF: Climbing fiber. GC: Granule cell. PF: Parallel fiber. PC: Purkinje cell. GgC: Golgi cell. SC: Stellate cell. BC: Basket cell.
Figure 6: Confocal micrograph from mouse cerebellum expressing green-fluorescent protein in Purkinje cells.

There are three layers to the cerebellar cortex; from outer to inner layer, these are the molecular, Purkinje, and granular layers. The function of the cerebellar cortex is essentially to modulate information flowing through the deep nuclei. The microcircuitry of the cerebellum is schematized in Figure 5. Mossy and climbing fibers carry sensorimotor information into the deep nuclei, which in turn pass it on to various premotor areas, thus regulating the gain and timing of motor actions. Mossy and climbing fibers also feed this information into the cerebellar cortex, which performs various computations, resulting in the regulation of Purkinje cell firing. Purkinje neurons feed back into the deep nuclei via a potent inhibitory synapse. This synapse regulates the extent to which mossy and climbing fibers activate the deep nuclei, and thus control the ultimate effect of the cerebellum on motor function. The synaptic strength of almost every synapse in the cerebellar cortex has been shown to undergo synaptic plasticity. This allows the circuitry of the cerebellar cortex to continuously adjust and fine-tune the output of the cerebellum, forming the basis of some types of motor learning and coordination. Each layer in the cerebellar cortex contains the various cell types that comprise this circuitry. Image File history File links Diagram of the cerebellar circuitry. ... Image File history File links Diagram of the cerebellar circuitry. ... Mossy fibers or mossy cells provide stimulation to inhibitory GABA interneurons in the hippocampus. ... In anatomy, the olivary bodies or simply olives (Latin oliva) are a pair of prominent oval structures in the medulla oblongata, the lower portion of the brainstem. ... Climbing fibers are the name given to a series of neuronal projections from the inferior olivary nucleus located in the medulla. ... Parallel fibers arise from granule cells in the cerebellar cortex. ... Drawing of pigeon Purkinje cells (A) by Santiago Ramon y Cajal Purkinje cells are a class of GABAergic neuron located in the cerebellar cortex. ... Image File history File links Confocal micrograph of cerebellum from transgenic mouse expressing EGFP driven by an L7, Purkinje cell-specific promoter. ... Image File history File links Confocal micrograph of cerebellum from transgenic mouse expressing EGFP driven by an L7, Purkinje cell-specific promoter. ... Confocal laser scanning microscopy (CLSM or LSCM) is a valuable tool for obtaining high resolution images and 3-D reconstructions. ... A micrograph is a photograph or similar image taken through a microscope or similar device to show a magnified image of an item. ... Feral mouse A mouse is a mammal that belongs to one of numerous species of small rodents in the genus Mus and various related genera of the family Muridæ (Old World Mice). ... ... Mossy fibers or mossy cells provide stimulation to inhibitory GABA interneurons in the hippocampus. ... Climbing fibers are the name given to a series of neuronal projections from the inferior olivary nucleus located in the medulla. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Illustration of the major elements in a prototypical synapse. ... The term synaptic plasticity refers to the variability of the strength of a signal transmitted through a synapse. ...


Granular layer

The innermost layer contains the cell bodies of two types of cells: the numerous and tiny granule cells, and the larger Golgi cells. Mossy fibers enter the granular layer from their main point of origin, the pontine nuclei. These fibers form excitatory synapses with the granule cells and the cells of the deep cerebellar nuclei. The granule cells send their axons—known as parallel fibers—up into the superficial molecular layer, where they form hundreds of thousands of synapses with Purkinje cell dendrites. Humans are estimated to have in the order of 1010 granule cells. Golgi cells provide inhibitory feedback to granule cells, forming a synapse with them and projecting an axon into the molecular layer. In neuroscience, granule cells are tiny cells found within the granular layer of the cerebellum. ... In neuroscience, Golgi cells are inhibitory interneurons found within the granular layer of the cerebellum. ... Parallel fibers arise from granule cells in the cerebellar cortex. ... In biology, a dendrite is a slender, typically branched projection of a nerve cell, or neuron, which conducts the electrical stimulation received from other cells to the body or soma of the cell from which it projects. ...


Purkinje layer

The middle layer contains only one type of cell body—that of the large Purkinje cell. Purkinje cell dendrites are large arbors with hundreds of spiny branches reaching up into the molecular layer (Fig. 6). These dendritic arbors are flat—nearly all of them lie in planes—with neighboring Purkinje arbors in parallel planes. Each parallel fiber from the granule cells runs orthogonally through these arbors, like a wire passing through many layers. Purkinje neurons are GABAergic—meaning they have inhibitory synapses—with the neurons of the deep cerebellar and vestibular nuclei in the brainstem. Each Purkinje cell receives excitatory input from 100,000 to 200,000 parallel fibers. Parallel fibers are said to be responsible for the simple (all or nothing, amplitude invariant) spiking of the Purkinje cell. In mathematics, orthogonal is synonymous with perpendicular when used as a simple adjective that is not part of any longer phrase with a standard definition. ... Amplitude is a nonnegative scalar measure of a waves magnitude of oscillation. ...


Purkinje cells also receive input from the inferior olivary nucleus via climbing fibers. A good mnemonic for this interaction is the phrase "climb the olive tree", given that climbing fibers originate from the inferior olive. Each Purkinje cell receives input from a single climbing fiber in the form of a powerful excitatory signal. These action potentials are of a rare class in that the excitatory postsynaptic response from climbing fibers are amplitude variant. These responses are known as complex spikes. In anatomy, the olivary bodies or simply olives (Latin oliva) are a pair of prominent oval structures in the medulla oblongata, the lower portion of the brainstem. ... Climbing fibers are the name given to a series of neuronal projections from the inferior olivary nucleus located in the medulla. ... A. Schematic of an electrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. ...


Molecular layer

This outermost layer of the cerebellar cortex contains two types of inhibitory interneurons: the stellate and basket cells. It also contains the dendritic arbors of Purkinje neurons and parallel fiber tracts from the granule cells. Both stellate and basket cells form GABAergic synapses onto Purkinje cell dendrites. Interneuron: noun An interneuron is a neuron that communicates only to other neurons. ... In neuroscience, stellate cells are inhibitory interneurons found within the molecular layer of the cerebellum. ... Basket cells are inhibitory GABAergic interneurons found in the molecular layer of the cerebellum. ...


Peduncles

Similarly, the cerebellum follows the trend of "threes", with three major input and output peduncles (fiber bundles). These are the superior (brachium conjunctivum), middle (brachium pontis), and inferior (restiform body) cerebellar peduncles. There are three sources of input to the cerebellum, in two categories consisting of mossy and climbing fibers, respectively. Mossy fibers can originate from the pontine nuclei, which are clusters of neurons located in the pons that carry information from the contralateral cerebral cortex. They may also arise within the spinocerebellar tract whose origin is located in the ipsilateral spinal cord. Most of the output from the cerebellum initially synapses onto the deep cerebellar nuclei before exiting via the three peduncles. The most notable exception is the direct inhibition of the vestibular nuclei by Purkinje cells. The anatomical planes The anatomical position is a schematic convention for describing the relative morphology of the human body. ... The spinal cord is a part of the vertebrate nervous system that is enclosed in and protected by the vertebral column (it passes through the spinal canal). ...


Superior cerebellar peduncle

While there are some afferent fibers from the anterior spinocerebellar tract that are conveyed to the anterior cerebellar lobe via this peduncle, most of the fibers are efferents. Thus, the superior cerebellar peduncle is the major output pathway of the cerebellum. . Most of the efferent fibers originate within the dentate nucleus which in turn project to various midbrain structures including the red nucleus, the ventral lateral/ventral anterior nucleus of the thalamus, and the medulla. The dentatorubrothalamocortical (dentate nucleus > red nucleus > thalamus > premotor cortex) and cerebellothalamocortical (cerebellum > thalamus > premotor cortex) pathways are two major pathways that pass through this peduncle and are important in motor planning. In biological anatomy, the mesencephalon (or midbrain) is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals. ... The red nucleus is a structure in the rostral midbrain involved in motor coordination. ... The thalamus is a part of the brain. ... Medulla can refer to: The medulla oblongata, a part of the brainstem Medulla, Florida, a U.S. city The 2004 music album Medúlla by Icelandic singer Björk. ...


Middle cerebellar peduncle

This is composed entirely of afferent fibers originating within the pontine nuclei as part of the massive corticopontocerebellar (cerebral cortex > pons > cerbellum) tract. These fibers descend from the sensory and motor areas of the cerebral neocortex and make the middle cerebellar peduncle the largest of the three cerebellar peduncles. In the anatomy of animals, the neopallium or neocortex is a part of the telencephalon in the brain. ...


Inferior cerebellar peduncle

This carries many types of input and output fibers that are mainly concerned with integrating proprioceptive sensory input with motor vestibular functions such as balance and posture maintenance. Proprioceptive information from the body is carried to the cerebellum via the posterior spinocerebellar tract. This tract passes through the inferior cerebellar peduncle and synapses within the paleocerebellum. Vestibular information projects onto the archicerebellum. This peduncle also carries information directly from the Purkinje cells to the vestibular nuclei in the dorsal brainstem located at the junction between the pons and medulla.


Blood supply

Figure 7: The three major arteries of the cerebellum: the SCA, AICA, and PICA.
Figure 7: The three major arteries of the cerebellum: the SCA, AICA, and PICA.

Three arteries supply blood to the cerebellum (Fig. 7): the superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), and posterior inferior cerebellar artery (PICA). Image File history File links Diagram of cerebellum blood supply. ... Image File history File links Diagram of cerebellum blood supply. ...


Superior cerebellar artery

The SCA branches off the lateral portion of the basilar artery, just inferior to its bifurcation into the posterior cerebral artery. Here it wraps posteriorly around the pons (to which it also supplies blood) before reaching the cerebellum. The SCA supplies blood to most of the cerebellar cortex, the cerebellar nuclei, and the middle and superior cerebellar peduncles.


Anterior inferior cerebellar artery

The AICA branches off the lateral portion of the basilar artery, just superior to the junction of the vertebral arteries. From its origin, it branches along the most inferior portion of the pons at the cerebellopontine angle before reaching the cerebellum. This artery supplies blood to the anterior portion of the inferior cerebellum, and to the facial (CN VII) and vestibulocochlear nerves (CN VIII). The facial nerve is seventh of twelve paired cranial nerves. ... Ricky is the best ...


Obstruction of the AICA can cause paresis, paralysis, and loss of sensation in the face; it can also cause hearing impairment. During the nineteenth century general paresis of the insane emerged as a new psychiatric disorder which was extremely common and completely devastating. ... Paralysis is the complete loss of muscle function for one or more muscle groups. ... This article needs to be cleaned up to conform to a higher standard of quality. ...


Posterior inferior cerebellar artery

The PICA branches off the lateral portion of the vertebral arteries just inferior to their junction with the basilar artery. Before reaching the inferior surface of the cerebellum, the PICA sends branches into the medulla, supplying blood to several cranial nerve nuclei. In the cerebellum, the PICA supplies blood to the posterior inferior portion of the cerebellum, the inferior cerebellar peduncle, the nucleus ambiguus, the vagus motor nucleus, the spinal trigeminal nucleus, the solitary nucleus, and the vestibulocochlear nuclei. Cranial nerves are nerves which start directly from the brainstem instead of the spinal cord. ... The nucleus ambiguus is a cranial nerve nucleus, located in the medulla oblongata, and handles the branchial motor functions of the ninth (glossopharyngeal) and tenth (vagus) cranial nerves. ... The vagus nerve is tenth of twelve cranial nerves and the only nerve that starts in the brainstem (somewhere in the medulla oblongata) and extends way down past the head, all the way down to the abdomen. ... The trigeminal nerve is the fifth (V) cranial nerve, and carries sensory information from most of the face, as well as motor supply to the muscles of mastication (the muscles enabling chewing), tensor tympani (in the ear) and other muscles in the floor of the mouth. ... The solitary nucleus and tract are structures in the brainstem that carry and receive visceral sensation and taste from the facial (VII), glossopharyngeal (IX), vagus (X) cranial nerves, as well as the cranial part of the accessory nerve (XI). ... Ricky is the best ...


Dysfunction

Patients with cerebellar dysfunction experience problems in walking, balance, and accurate hand and arm movement. Recent brain imaging studies using functional magnetic resonance imaging (fMRI) show that the cerebellum is important for language processing and selective attention. Neuropsychiatric disorders such as dyslexia and autism appear to be associated with a deficiency in the cerebellum, which may also play a role in the development of certain ataxias, including a form of cerebral palsy. Spinocerebellar ataxia patients suffer cerebellar degeneration. Opsoclonus myoclonus syndrome is thought to be caused by an autoimmune attack on the cerebellum among other brain regions. Functional Magnetic Resonance Imaging (or fMRI) describes the use of MRI to measure the hemodynamic response related to neural activity in the brain or spinal cord of humans or other animals. ... Language processing refers to the way human beings process speech or writing and understand it as language. ... Selective attention . ... The Scream, the famous painting commonly thought of as depicting the experience of mental illness. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Autism is classified as a neurodevelopmental disorder that manifests itself in markedly abnormal social interaction, communication ability, patterns of interests, and patterns of behavior. ... Ataxia (from Greek ataxiā, meaning failure to put in order) is unsteady and clumsy motion of the limbs or trunk due to a failure of the fine coordination of muscle movements. ... Cerebral palsy or CP is a group of permanent disorders associated with developmental brain injuries that occur during fetal development, birth, or shortly after birth. ... Cerebellum (in blue) of the human brain Spinocerebellar ataxia (SCA) is a disease with multiple types, each of which could be considered a disease in its own right. ... Opsoclonus myoclonus syndrome (OMS) is a rare neurological disorder of unknown causes which appears to be the result of an autoimmune process involving the nervous system. ...


Lesions of the cerebellum

Patients with cerebellar lesions (injuries) typically exhibit deficits during movement execution. For example, they show "intention tremors"—a tremor occurring during movement rather than at rest, as seen in Parkinson’s Disease. Patients may also show dysmetria, i.e., an overestimation or underestimation of force, resulting in overshoot or undershoot when reaching for a target. Another common sign of cerebellar damage is an inability to perform rapid alternating movements. A lesion is a non-specific term referring to abnormal tissue in the body. ... Parkinsons disease (PD; paralysis agitans) is a neurodegenerative disease of the substantia nigra (an area in the basal ganglia of the brain). ... Dysmetria (Greek: dificult to measure) is a symptom exhibited by patients after cerebellar injury. ...


The anterior and medial aspects of the cerebellum represent information ipsilaterally; thus damage to this region on one side affects the movement on the same side of the body. The posterior and lateral aspects of the cerebellum represent information bilaterally; damage to this region has been shown to impair sensory–motor adaptation, while leaving motor control unaffected. In certain instances, a patient experiences a very focal lesion. Such localized lesions cause a wide variety of symptoms related to their location in the cerebellum. A striking example is archicerebellar lesions, which cause motor symptoms not unlike those seen during intoxication: uncoordinated movements, swaying, unstable walking, and a wide gait. To avoid suspicion by the police of public drunkenness, American patients who suffer archicerebellar lesions carry identification cards written by their physicians, indicating their medical condition. This article or section should include material from drunkenness Intoxication is an impaired mental and physical state caused by ingesting alcoholic beverages or other psychoactive drugs. ... German identity document sample An identity document is a piece of documentation designed to prove the identity of the person carrying it. ...


A lesion to the paleocerebellum causes severe disturbance in muscle tone and bodily posture, resulting in weakness to the side of the body opposite the lesion. A neocerebellar lesion is associated with deficits in skilled voluntary movement, such as playing the piano. A lesion to the intermediate zone causes problems with fine-tuning and corrective movements. Patients with this type of lesion who hold their fingers in front of them have great difficulty in moving those fingers together. Patients with a lesion to the lateral zone have difficulty in controlling fine muscle movements and exhibit symptoms similar to those of patients with an intermediate zone lesion.


Alcohol abuse is also a common cause of cerebellar lesions. Alcohol abuse can lead to thiamine deficiency, which in the cerebellum will cause degeneration of the anterior lobe. This degeneration leads to a wide, staggering gait but does not affect arm movement or speech[3]. This article needs cleanup. ... Thiamine mononitrate Thiamine or thiamin, also known as vitamin B1, is a colorless compound with chemical formula C12H17ClN4OS. It is soluble in water and insoluble in alcohol. ...


Ischemia and thrombosis

An obstruction of the posterior inferior cerebellar artery (known as 'PICA syndrome') can cause a wide range of characteristic effects. An obstruction of the artery causes cell death as the cells are deprived of oxygen and nutrients provided by the blood. PICA syndrome manifests as a loss of sensation in the contralateral limbs due to damage of the inferior cerebellar peduncle as well as dizziness and nausea due to loss of blood to the nucleus ambiguus and vestibulocochlear nuclei. Necrosis (in Greek Νεκρός = Dead) is the name given to unprogrammed death of cells/living tissue (compare with apoptosis - programmed cell death). ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ...


Theories about cerebellar function

Two main theories address the function of the cerebellum. One claims that the cerebellum functions as a regulator of the "timing of movements". This has emerged from studies of patients whose timed movements are disrupted[4]. The other theory claims that the cerebellum operates as a learning machine, encoding information as does a computer. This was first proposed by Marr and Albus in the early 1970s[5].


Like many controversies in the physical sciences, there is evidence supporting parts of both hypotheses. Studies of motor learning in the vestibulo-ocular reflex and eyeblink conditioning demonstrate that the timing and amplitude of learned movements are encoded by the cerebellum[6]. Many synaptic plasticity mechanisms have been found throughout the cerebellum. The Marr-Albus model mostly attributes motor learning to a single plasticity mechanism: the long-term depression of parallel fiber synapses. Figure 3 Three-neuron arc, during a head movement to the right. ... Eyeblink conditioning is a form of classical conditioning in which animals are trained to blink in response to a tone. ... Amplitude is a nonnegative scalar measure of a waves magnitude of oscillation. ... The term synaptic plasticity refers to the variability of the strength of a signal transmitted through a synapse. ... Long-term depression (LTD) is a weakening of a synapse that lasts from hours to days. ...


With the advent of more sophisticated neuroimaging techniques such as positron emission tomography (PET)[7] and fMRI[8], numerous diverse functions are now at least partially attributed to the cerebellum. What was once thought to be primarily a motor/sensory integration region is now proving to be involved in many diverse cognitive functions. Paradoxically, despite the importance of this region and the heterogeneous role it plays in motor and sensory functions, people who have lost their entire cerebellum through disease, injury, or surgery can live reasonably normal lives. Neuroimaging is the term used for all invasive, minimally invasive and non-invasive methods and techniques used for obtaing structural and functional images of the nervous system, i. ... Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three dimensional image or map of functional processes in the body. ...


Cerebellar modeling

As mentioned in the preceding section, there have been many attempts to model the cerebellar function. The insights provided by the models have also led to extrapolations in the domains of artificial intelligence methodologies, especially neural networks. Some of the notable acheivements hava been Cerebellatron [9], Cerebellar Model Associative Memory or CMAC netorks [10] and Spikeforce [11] for robotic movement control. A mathematical model is an abstract model that uses mathematical language to describe the behaviour of a system. ... Artificial intelligence (also known as machine intelligence and often abbreviated as AI) is intelligence exhibited by any manufactured (i. ... A neural network is an interconnected group of neurons. ...


See also

In the anatomy of animals, the brain, or encephalon, is the supervisory center of the nervous system. ... The Central Nervous System (CNS) represents the largest part of the Nervous System. ... Human brain image constructed from MRI data // Brain (neural tube) Brainstem (rhombencephalon),(mesencephalon) Rhombencephalon (hindbrain) Metencephalon pons fourth ventricle cerebellum cerebellar vermis cerebellar hemispheres anterior lobe posterior lobe flocculonodular lobe cerebellar nuclei fastigial nucleus globose nucleus emboliform nucleus dentate nucleus Myelencephalon medulla oblongata medullary pyramids Mesencephalon (midbrain) tectum inferior colliculi...

External links

Further reading

  • Ito M. Cerebellum and Neural Control. New York: Raven Press; 1984. ISBN 0890041067
  • Kandel E, Schwartz J, Jessel T. Principles of Neural Science. 4th ed. New York: McGraw-Hill; 2000. ISBN 0838577016
  • Llinás, R, Sotelo C. The Cerebellum Revisited. New York: Springer; 1992. ISBN 0387976930
  • Parent A, Carpenter MB. Carpenter's Human Neuroanatomy. 9th ed. Philadelphia: Williams and Wilkins; 1995. ISBN 0683067524

References

  1. Fine EJ, Ionita CC, Lohr L. The History of the development of the cerebellar examination. Semin Neurol. 2002;22(4):375–84. PMID 12539058
  2. Muller F, O'Rahilly R. The human brain at stages 21–23, with particular reference to the cerebral cortical plate and to the development of the cerebellum. Anat Embryol (Berl). 1990;182(4):375–400. PMID 2252222
  3. Sereni C, Degos CF. [Lesions of the brain stem and cerebellum of alcoholic and nutritional deficiency origin.] Rev Prat. 1990;40(13):1193–96. (in French) PMID 2343251
  4. Ivry RB, Keele SW, Diener HC. Dissociation of the lateral and medial cerebellum in movement timing and movement execution. Exp Brain Res. 1988;73(1):167–80. PMID 3208855
  5. Marr D. A theory of cerebellar cortex. J Physiol 1969;202(2):437-70. PMID 5784296
  6. Boyden ES, Katoh A, Raymond JL. Cerebellum-dependent learning: The role of multiple plasticity mechanisms. Annu Rev Neurosci. 2004;27:581–609 PMID 15217344
  7. Obayashi S. Possible mechanism for transfer of motor skill learning: implication of the cerebellum. Cerebellum. 2004;3(4):204–11. PMID 15686098
  8. Kim SG, Ugurbil K, Strick PL. Activation of a cerebellar output nucleus during cognitive processing. Science. 1994;265(5174):949–51. PMID 8052851

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(noo´kle-on) a particle of the atomic nucleus, a proton or a neutron.
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