Dendritic Spines: Spiny processes on DENDRITES, each of which receives excitatory input from one nerve ending (NERVE ENDINGS). They are commonly found on PURKINJE CELLS and PYRAMIDAL CELLS.Spine: The spinal or vertebral column.Dendrites: Extensions of the nerve cell body. They are short and branched and receive stimuli from other NEURONS.Synapses: Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.Hippocampus: A curved elevation of GRAY MATTER extending the entire length of the floor of the TEMPORAL HORN of the LATERAL VENTRICLE (see also TEMPORAL LOBE). The hippocampus proper, subiculum, and DENTATE GYRUS constitute the hippocampal formation. Sometimes authors include the ENTORHINAL CORTEX in the hippocampal formation.Neuronal Plasticity: The capacity of the NERVOUS SYSTEM to change its reactivity as the result of successive activations.Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Pyramidal Cells: Projection neurons in the CEREBRAL CORTEX and the HIPPOCAMPUS. Pyramidal cells have a pyramid-shaped soma with the apex and an apical dendrite pointed toward the pial surface and other dendrites and an axon emerging from the base. The axons may have local collaterals but also project outside their cortical region.Silver Staining: The use of silver, usually silver nitrate, as a reagent for producing contrast or coloration in tissue specimens.Receptors, N-Methyl-D-Aspartate: A class of ionotropic glutamate receptors characterized by affinity for N-methyl-D-aspartate. NMDA receptors have an allosteric binding site for glycine which must be occupied for the channel to open efficiently and a site within the channel itself to which magnesium ions bind in a voltage-dependent manner. The positive voltage dependence of channel conductance and the high permeability of the conducting channel to calcium ions (as well as to monovalent cations) are important in excitotoxicity and neuronal plasticity.Receptors, AMPA: A class of ionotropic glutamate receptors characterized by their affinity for the agonist AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid).CA1 Region, Hippocampal: One of four subsections of the hippocampus described by Lorente de No, located furthest from the DENTATE GYRUS.Post-Synaptic Density: Cytoskeleton specialization at the cytoplasmic side of postsynaptic membrane in SYNAPSES. It is involved in neuronal signaling and NEURONAL PLASTICITY and comprised of GLUTAMATE RECEPTORS; scaffolding molecules (e.g., PSD95, PSD93), and other proteins (e.g., CaCMKII).Nerve Tissue ProteinsLong-Term Potentiation: A persistent increase in synaptic efficacy, usually induced by appropriate activation of the same synapses. The phenomenological properties of long-term potentiation suggest that it may be a cellular mechanism of learning and memory.Microscopy, Confocal: A light microscopic technique in which only a small spot is illuminated and observed at a time. An image is constructed through point-by-point scanning of the field in this manner. Light sources may be conventional or laser, and fluorescence or transmitted observations are possible.Excitatory Postsynaptic Potentials: Depolarization of membrane potentials at the SYNAPTIC MEMBRANES of target neurons during neurotransmission. Excitatory postsynaptic potentials can singly or in summation reach the trigger threshold for ACTION POTENTIALS.Cervical Vertebrae: The first seven VERTEBRAE of the SPINAL COLUMN, which correspond to the VERTEBRAE of the NECK.Green Fluorescent Proteins: Protein analogs and derivatives of the Aequorea victoria green fluorescent protein that emit light (FLUORESCENCE) when excited with ULTRAVIOLET RAYS. They are used in REPORTER GENES in doing GENETIC TECHNIQUES. Numerous mutants have been made to emit other colors or be sensitive to pH.Synaptic Transmission: The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.Lumbar Vertebrae: VERTEBRAE in the region of the lower BACK below the THORACIC VERTEBRAE and above the SACRAL VERTEBRAE.Guanylate Kinase: Catalyzes the ATP-dependent PHOSPHORYLATION of GMP to generate GDP and ADP.Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Spinal DiseasesCell Surface Extensions: Specialized structures of the cell that extend the cell membrane and project out from the cell surface.Actins: Filamentous proteins that are the main constituent of the thin filaments of muscle fibers. The filaments (known also as filamentous or F-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 amino acids long. This is known as globular or G-actin. In conjunction with MYOSINS, actin is responsible for the contraction and relaxation of muscle.Pseudopodia: A dynamic actin-rich extension of the surface of an animal cell used for locomotion or prehension of food.Organ Culture Techniques: A technique for maintenance or growth of animal organs in vitro. It refers to three-dimensional cultures of undisaggregated tissue retaining some or all of the histological features of the tissue in vivo. (Freshney, Culture of Animal Cells, 3d ed, p1)Cerebral Cortex: The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulchi. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.Microfilament Proteins: Monomeric subunits of primarily globular ACTIN and found in the cytoplasmic matrix of almost all cells. They are often associated with microtubules and may play a role in cytoskeletal function and/or mediate movement of the cell or the organelles within the cell.Presynaptic Terminals: The distal terminations of axons which are specialized for the release of neurotransmitters. Also included are varicosities along the course of axons which have similar specializations and also release transmitters. Presynaptic terminals in both the central and peripheral nervous systems are included.Spinal Injuries: Injuries involving the vertebral column.Receptors, Glutamate: Cell-surface proteins that bind glutamate and trigger changes which influence the behavior of cells. Glutamate receptors include ionotropic receptors (AMPA, kainate, and N-methyl-D-aspartate receptors), which directly control ion channels, and metabotropic receptors which act through second messenger systems. Glutamate receptors are the most common mediators of fast excitatory synaptic transmission in the central nervous system. They have also been implicated in the mechanisms of memory and of many diseases.Purkinje Cells: The output neurons of the cerebellar cortex.Calcium-Calmodulin-Dependent Protein Kinase Type 2: A multifunctional calcium-calmodulin-dependent protein kinase subtype that occurs as an oligomeric protein comprised of twelve subunits. It differs from other enzyme subtypes in that it lacks a phosphorylatable activation domain that can respond to CALCIUM-CALMODULIN-DEPENDENT PROTEIN KINASE KINASE.Microscopy, Fluorescence, Multiphoton: Fluorescence microscopy utilizing multiple low-energy photons to produce the excitation event of the fluorophore. Multiphoton microscopes have a simplified optical path in the emission side due to the lack of an emission pinhole, which is necessary with normal confocal microscopes. Ultimately this allows spatial isolation of the excitation event, enabling deeper imaging into optically thick tissue, while restricting photobleaching and phototoxicity to the area being imaged.Mice, Inbred C57BLBrain-Derived Neurotrophic Factor: A member of the nerve growth factor family of trophic factors. In the brain BDNF has a trophic action on retinal, cholinergic, and dopaminergic neurons, and in the peripheral nervous system it acts on both motor and sensory neurons. (From Kendrew, The Encyclopedia of Molecular Biology, 1994)Thoracic Vertebrae: A group of twelve VERTEBRAE connected to the ribs that support the upper trunk region.Receptors, Eph Family: A large family of receptor protein-tyrosine kinases that are structurally-related. The name of this family of proteins derives from original protein Eph (now called the EPHA1 RECEPTOR), which was named after the cell line it was first discovered in: Erythropoietin-Producing human Hepatocellular carcinoma cell line. Members of this family have been implicated in regulation of cell-cell interactions involved in nervous system patterning and development.Endoplasmic Reticulum, Smooth: A type of endoplasmic reticulum lacking associated ribosomes on the membrane surface. It exhibits a wide range of specialized metabolic functions including supplying enzymes for steroid synthesis, detoxification, and glycogen breakdown. In muscle cells, smooth endoplasmic reticulum is called SARCOPLASMIC RETICULUM.Cell Shape: The quality of surface form or outline of CELLS.Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Models, Neurological: Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.Fragile X Mental Retardation Protein: A RNA-binding protein that is found predominately in the CYTOPLASM. It helps regulate GENETIC TRANSLATION in NEURONS and is absent or under-expressed in FRAGILE X SYNDROME.Animals, Newborn: Refers to animals in the period of time just after birth.Luminescent Proteins: Proteins which are involved in the phenomenon of light emission in living systems. Included are the "enzymatic" and "non-enzymatic" types of system with or without the presence of oxygen or co-factors.Guanine Nucleotide Exchange Factors: Protein factors that promote the exchange of GTP for GDP bound to GTP-BINDING PROTEINS.Biolistics: Techniques where DNA is delivered directly into organelles at high speed using projectiles coated with nucleic acid, shot from a helium-powered gun (gene gun). One of these techniques involves immunization by DNA VACCINES, which delivers DNA-coated gold beads to the epidermis.Microscopy, Electron: Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.Somatosensory Cortex: Area of the parietal lobe concerned with receiving sensations such as movement, pain, pressure, position, temperature, touch, and vibration. It lies posterior to the central sulcus.Excitatory Amino Acid Antagonists: Drugs that bind to but do not activate excitatory amino acid receptors, thereby blocking the actions of agonists.Fragile X Syndrome: A condition characterized genotypically by mutation of the distal end of the long arm of the X chromosome (at gene loci FRAXA or FRAXE) and phenotypically by cognitive impairment, hyperactivity, SEIZURES, language delay, and enlargement of the ears, head, and testes. INTELLECTUAL DISABILITY occurs in nearly all males and roughly 50% of females with the full mutation of FRAXA. (From Menkes, Textbook of Child Neurology, 5th ed, p226)Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Embryo, Mammalian: The entity of a developing mammal (MAMMALS), generally from the cleavage of a ZYGOTE to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the FETUS.Microscopy, Immunoelectron: Microscopy in which the samples are first stained immunocytochemically and then examined using an electron microscope. Immunoelectron microscopy is used extensively in diagnostic virology as part of very sensitive immunoassays.Glutamic Acid: A non-essential amino acid naturally occurring in the L-form. Glutamic acid is the most common excitatory neurotransmitter in the CENTRAL NERVOUS SYSTEM.Dentate Gyrus: GRAY MATTER situated above the GYRUS HIPPOCAMPI. It is composed of three layers. The molecular layer is continuous with the HIPPOCAMPUS in the hippocampal fissure. The granular layer consists of closely arranged spherical or oval neurons, called GRANULE CELLS, whose AXONS pass through the polymorphic layer ending on the DENDRITES of PYRAMIDAL CELLS in the hippocampus.Spinal Fusion: Operative immobilization or ankylosis of two or more vertebrae by fusion of the vertebral bodies with a short bone graft or often with diskectomy or laminectomy. (From Blauvelt & Nelson, A Manual of Orthopaedic Terminology, 5th ed, p236; Dorland, 28th ed)Neurogenesis: Formation of NEURONS which involves the differentiation and division of STEM CELLS in which one or both of the daughter cells become neurons.Synaptophysin: A MARVEL domain-containing protein found in the presynaptic vesicles of NEURONS and NEUROENDOCRINE CELLS. It is commonly used as an immunocytochemical marker for neuroendocrine differentiation.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Actin Depolymerizing Factors: A family of low MOLECULAR WEIGHT actin-binding proteins found throughout eukaryotes. They remodel the actin CYTOSKELETON by severing ACTIN FILAMENTS and increasing the rate of monomer dissociation.Neuropil: A dense intricate feltwork of interwoven fine glial processes, fibrils, synaptic terminals, axons, and dendrites interspersed among the nerve cells in the gray matter of the central nervous system.Receptor, EphB2: An eph family receptor found widely expressed in embryonic and adult tissues. High levels of EphB2 receptor are observed in growing AXONS and NERVE FIBERS. Several isoforms of the protein exist due to multiple alternative mRNA splicing.Intracellular Signaling Peptides and Proteins: Proteins and peptides that are involved in SIGNAL TRANSDUCTION within the cell. Included here are peptides and proteins that regulate the activity of TRANSCRIPTION FACTORS and cellular processes in response to signals from CELL SURFACE RECEPTORS. Intracellular signaling peptide and proteins may be part of an enzymatic signaling cascade or act through binding to and modifying the action of other signaling factors.Neocortex: The largest portion of the CEREBRAL CORTEX in which the NEURONS are arranged in six layers in the mammalian brain: molecular, external granular, external pyramidal, internal granular, internal pyramidal and multiform layers.Patch-Clamp Techniques: An electrophysiologic technique for studying cells, cell membranes, and occasionally isolated organelles. All patch-clamp methods rely on a very high-resistance seal between a micropipette and a membrane; the seal is usually attained by gentle suction. The four most common variants include on-cell patch, inside-out patch, outside-out patch, and whole-cell clamp. Patch-clamp methods are commonly used to voltage clamp, that is control the voltage across the membrane and measure current flow, but current-clamp methods, in which the current is controlled and the voltage is measured, are also used.Prefrontal Cortex: The rostral part of the frontal lobe, bounded by the inferior precentral fissure in humans, which receives projection fibers from the MEDIODORSAL NUCLEUS OF THE THALAMUS. The prefrontal cortex receives afferent fibers from numerous structures of the DIENCEPHALON; MESENCEPHALON; and LIMBIC SYSTEM as well as cortical afferents of visual, auditory, and somatic origin.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Maze Learning: Learning the correct route through a maze to obtain reinforcement. It is used for human or animal populations. (Thesaurus of Psychological Index Terms, 6th ed)Synaptic Membranes: Cell membranes associated with synapses. Both presynaptic and postsynaptic membranes are included along with their integral or tightly associated specializations for the release or reception of transmitters.Receptor, EphA4: An eph family receptor found in variety of tissues including BRAIN. During embryogenesis, EphA4 receptor exhibits a diverse spatial and temporal patterns of expression suggesting its role in multiple developmental processes.Fluorescence Recovery After Photobleaching: A method used to study the lateral movement of MEMBRANE PROTEINS and LIPIDS. A small area of a cell membrane is bleached by laser light and the amount of time necessary for unbleached fluorescent marker-tagged proteins to diffuse back into the bleached site is a measurement of the cell membrane's fluidity. The diffusion coefficient of a protein or lipid in the membrane can be calculated from the data. (From Segen, Current Med Talk, 1995).Memory: Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory.Cytoskeleton: The network of filaments, tubules, and interconnecting filamentous bridges which give shape, structure, and organization to the cytoplasm.Membrane Proteins: Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.rac1 GTP-Binding Protein: A rac GTP-binding protein involved in regulating actin filaments at the plasma membrane. It controls the development of filopodia and lamellipodia in cells and thereby influences cellular motility and adhesion. It is also involved in activation of NADPH OXIDASE. This enzyme was formerly listed as EC 3.6.1.47.Chimerin 1: A GTPase activating protein that is specific for RAC GTP-BINDING PROTEINS. It is expressed primarily in the brain and may be involved in signal transduction. The alternatively spliced form of CHIMERIN 1 (alpha-2 Chimerin) contains an additional src homology domain and is expressed in both the brain and testes.Learning: Relatively permanent change in behavior that is the result of past experience or practice. The concept includes the acquisition of knowledge.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Spinal Fractures: Broken bones in the vertebral column.Spinal NeoplasmsSyndecan-2: A syndecan that is predominantly expressed during EMBRYONIC DEVELOPMENT. It may play a role in mediating cellular interactions with the EXTRACELLULAR MATRIX and may modulate the signaling activity of certain INTERCELLULAR SIGNALING PEPTIDES AND PROTEINS.Cortactin: A microfilament protein that interacts with F-ACTIN and regulates cortical actin assembly and organization. It is also an SH3 DOMAIN containing phosphoprotein, and it mediates tyrosine PHOSPHORYLATION based SIGNAL TRANSDUCTION by PROTO-ONCOGENE PROTEIN PP60(C-SRC).Axons: Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.GTPase-Activating Proteins: Proteins that activate the GTPase of specific GTP-BINDING PROTEINS.N-Methylaspartate: An amino acid that, as the D-isomer, is the defining agonist for the NMDA receptor subtype of glutamate receptors (RECEPTORS, NMDA).Protein Transport: The process of moving proteins from one cellular compartment (including extracellular) to another by various sorting and transport mechanisms such as gated transport, protein translocation, and vesicular transport.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Calcium Signaling: Signal transduction mechanisms whereby calcium mobilization (from outside the cell or from intracellular storage pools) to the cytoplasm is triggered by external stimuli. Calcium signals are often seen to propagate as waves, oscillations, spikes, sparks, or puffs. The calcium acts as an intracellular messenger by activating calcium-responsive proteins.Nucleus Accumbens: Collection of pleomorphic cells in the caudal part of the anterior horn of the LATERAL VENTRICLE, in the region of the OLFACTORY TUBERCLE, lying between the head of the CAUDATE NUCLEUS and the ANTERIOR PERFORATED SUBSTANCE. It is part of the so-called VENTRAL STRIATUM, a composite structure considered part of the BASAL GANGLIA.Image Cytometry: A technique encompassing morphometry, densitometry, neural networks, and expert systems that has numerous clinical and research applications and is particularly useful in anatomic pathology for the study of malignant lesions. The most common current application of image cytometry is for DNA analysis, followed by quantitation of immunohistochemical staining.Transfection: The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.Bone Density: The amount of mineral per square centimeter of BONE. This is the definition used in clinical practice. Actual bone density would be expressed in grams per milliliter. It is most frequently measured by X-RAY ABSORPTIOMETRY or TOMOGRAPHY, X RAY COMPUTED. Bone density is an important predictor for OSTEOPOROSIS.Vesicular Glutamate Transport Protein 1: A vesicular glutamate transporter protein that is predominately expressed in TELENCEPHALON of the BRAIN.Long-Term Synaptic Depression: A persistent activity-dependent decrease in synaptic efficacy between NEURONS. It typically occurs following repeated low-frequency afferent stimulation, but it can be induced by other methods. Long-term depression appears to play a role in MEMORY.Rats, Wistar: A strain of albino rat developed at the Wistar Institute that has spread widely at other institutions. This has markedly diluted the original strain.Synaptic Potentials: The voltages across pre- or post-SYNAPTIC MEMBRANES.Cofilin 1: Cofilin 1 is a member of the cofilin family of proteins that is expressed in non-muscle CELLS. It has ACTIN depolymerization activity that is dependent on HYDROGEN-ION CONCENTRATION.Excitatory Amino Acids: Endogenous amino acids released by neurons as excitatory neurotransmitters. Glutamic acid is the most common excitatory neurotransmitter in the brain. Aspartic acid has been regarded as an excitatory transmitter for many years, but the extent of its role as a transmitter is unclear.Miniature Postsynaptic Potentials: Postsynaptic potentials generated from a release of neurotransmitters from a presynaptic nerve terminal in the absence of an ACTION POTENTIAL. They may be m.e.p.p.s (miniature EXCITATORY POSTSYNAPTIC POTENTIALS) or m.i.p.p.s (miniature INHIBITORY POSTSYNAPTIC POTENTIALS).Dynamin III: A subtype of dynamin found expressed exclusively in the testis, lung and brain.Carbocyanines: Compounds that contain three methine groups. They are frequently used as cationic dyes used for differential staining of biological materials.Neuropeptides: Peptides released by NEURONS as intercellular messengers. Many neuropeptides are also hormones released by non-neuronal cells.Ephrin-A3: A GLYCOINOSITOL PHOSPHOLIPID MEMBRANE ANCHOR containing ephrin with a high affinity for the EPHA3 RECEPTOR; EPHA5 RECEPTOR; EPHA6 RECEPTOR; EPHA7 RECEPTOR; and EPHA8 RECEPTOR. It is found primarily in NERVE TISSUE.Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Cerebellum: The part of brain that lies behind the BRAIN STEM in the posterior base of skull (CRANIAL FOSSA, POSTERIOR). It is also known as the "little brain" with convolutions similar to those of CEREBRAL CORTEX, inner white matter, and deep cerebellar nuclei. Its function is to coordinate voluntary movements, maintain balance, and learn motor skills.Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Synaptosomes: Pinched-off nerve endings and their contents of vesicles and cytoplasm together with the attached subsynaptic area of the membrane of the post-synaptic cell. They are largely artificial structures produced by fractionation after selective centrifugation of nervous tissue homogenates.Corpus Striatum: Striped GRAY MATTER and WHITE MATTER consisting of the NEOSTRIATUM and paleostriatum (GLOBUS PALLIDUS). It is located in front of and lateral to the THALAMUS in each cerebral hemisphere. The gray substance is made up of the CAUDATE NUCLEUS and the lentiform nucleus (the latter consisting of the GLOBUS PALLIDUS and PUTAMEN). The WHITE MATTER is the INTERNAL CAPSULE.Calcium: A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.