Cognitive Neuroscience Exam One

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Aggregate Field Theory

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Pierre Flourens, a French experimental psychologist, was one of many scientists that challenged the views of the phrenologists. Through his study of living rabbits and pigeons, he discovered that lesions to particular areas of the brain produced no discernible change in behavior. He proposed the theory that the brain is an aggregate field, meaning that different areas of the brain participated in behavior.

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Associationism

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Associationism is the theory that the mind is composed of elements -- usually referred to as sensations and ideas -- which are organized by means of various associations. Although the original idea can be found in Plato, it is Aristotle who gets the credit for elaborating on it. Aristotle counted four laws of association when he examined the processes of remembrance.

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Behaviorism

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learning perspective (where any physical action is a behavior), is a philosophy of psychology based on the proposition that all things that organisms do—including acting, thinking and feeling—can and should be regarded as behaviors.[1]

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Cognitive Neuroscience

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an academic field concerned with the scientific study of biological substrates underlying cognition[1], with a specific focus on the neural substrates of mental processes.

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Cytoarchitectonics

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the study of the cellular composition of the body's tissues under the microscope. The two terms can be used interchangeably but the latter term: Cytoarchitectonics, is more commonly found in neuroscience literatures.

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Empiricism

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a theory of knowledge that asserts that knowledge arises from evidence gathered via sense experience. Empiricism is one of several competing views that predominate in the study of human knowledge, known as epistemology. Empiricism emphasizes the role of experience and evidence, especially sensory perception, in the formation of ideas, over the notion of innate ideas or tradition [1] in contrast to, for example, rationalism which relies upon reason and can incorporate innate knowledge.

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Neuron Doctrine

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the now fundamental idea, formally proposed in 1891 by H. Waldeyer-Hartz, that the nervous system is made up of discrete individual cells.[1]

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Phrenology

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was especially popular from about 1810 until 1840. Following the materialist notions of mental functions originating in the brain, phrenologists believed that human conduct could best be understood in neurological rather than abstract terms. It is now considered a pseudoscience. Developed by German physician Franz Joseph Gall in 1796.

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Action Potential

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a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a stereotyped trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and endocrine cells. In neurons, they play a central role in cell-to-cell communication. In other types of cells, their main function is to activate intracellular processes. Action potentials in neurons are also known as "nerve impulses" or "spikes", and the temporal sequence of action potentials generated by a neuron is called its "spike train". A neuron that emits an action potential is often said to "fire".

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Axon

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a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma. An axon is one of two types of protoplasmic protrusions that extrude from the cell body of a neuron, the other type being dendrites. Axons are distinguished from dendrites by several features, including shape (dendrites often taper while axons usually maintain a constant radius), length (dendrites are restricted to a small region around the cell body while axons can be much longer), and function (dendrites usually receive signals while axons usually transmit them). All of these rules have exceptions, however.

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Blood-Brain Barrier (BBB)

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is a separation of circulating blood and cerebrospinal fluid (CSF) in the central nervous system (CNS). It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion of microscopic objects (e.g. bacteria) and large or hydrophilic molecules into the CSF, while allowing the diffusion of small hydrophobic molecules (O2, hormones, CO2). Cells of the barrier actively transport metabolic products such as glucose across the barrier with specific proteins.

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Dendrites

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are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project. Electrical stimulation is transmitted onto dendrites by upstream neurons via synapses which are located at various points throughout the dendritic arbor.

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Depolarization

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is a change in a cell's membrane potential, making it more positive, or less negative. In neurons and some other cells, a large enough depolarization may result in an action potential. Hyperpolarization is the opposite of depolarization, and inhibits the rise of an action potential.

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Electrical Gradient

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a spatial variation of both electrical potential and chemical concentration across a membrane. Both components are often due to ion gradients, particularly proton gradients, and the result can be a type of potential energy available for work in a cell. This can be calculated as a thermodynamic measure, termed electrochemical potential, that combines the concepts of energy stored in the form of chemical potential, which accounts for an ion's concentration gradient across a cellular membrane, and electrostatics, which accounts for an ion's tendency to move relative to the membrane potential.

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Electrotonic Conduction

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Changes in transmembrane potential which occur at specific locations along the neural membrane are not isolated, but spread to affect adjacent areas of the membrane. The spread of effect is not uniform: a depolarization, or its opposite, a hyperpolarization of the transmembrane potential at a given location on the membrane decays with distance (D), roughly as 1/D2. The spread and decay of the influence of electrical potential changes is called electrotonic conduction (synonyms include passive or decremental conduction).

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Equilibrium Potential

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A point in which forward and reverse reaction rates are equal in an electrolytic solution, thereby establishing the potential of an electrode.

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Glial Cell

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non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for the brain's neurons. In the human brain, there is roughly one glia for every neuron with a ratio of about two neurons for every three glia in the cerebral gray matter.

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Hyperpolarization

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a change in a cell's membrane potential that makes it more negative. It is the opposite of a depolarization.Hyperpolarization is often caused by efflux of K+ (a cation) through K+ channels, or influx of Cl– (an anion) through Cl– channels.

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Ion Channel

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are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of cells (see cell potential) by allowing the flow of ions down their electrochemical gradient.

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Myelin

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a dielectric (electrically insulating) material that forms a layer, the myelin sheath, usually around only the axon of a neuron. It is essential for the proper functioning of the nervous system. Myelin is an outgrowth of a glial cell. Schwann cells supply the myelin for peripheral neurons, whereas oligodendrocytes, specifically of the interfascicular type, myelinate the axons of the central nervous system.

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Neurotransmitter

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are endogenous chemicals which transmit signals from a neuron to a target cell across a synapse.[1] Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to receptors in the membrane on the postsynaptic side of the synapse. Release of neurotransmitters usually follows arrival of an action potential at the synapse, but may also follow graded electrical potentials. Low level "baseline" release also occurs without electrical stimulation.

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Node of Ranvier

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the gaps (approximately 1 micrometer in length) formed between the myelin sheaths generated by different cells. A myelin sheath is a many-layered coating, largely composed of a fatty substance called myelin, that wraps around the axon of a neuron and very efficiently insulates it. At nodes of Ranvier, the axonal membrane is uninsulated and therefore capable of generating electrical activity.

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Permeability

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is a membrane that will allow certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion". The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute. Depending on the membrane and the solute, permeability may depend on solute size, solubility, properties, or chemistry. How the membrane is constructed to be selective in its permeability will determine the rate and the permeability.

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Postsynaptic

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Situated behind or occurring after a synapse.

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Presynaptic

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Of, or relating to the transmitting end of a discharge across a synapse. Pertaining to or being situated at the proximal side of a synapse.

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Propagation

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The propagation of a nerve impulse along an axon begins when the synapses receives neurotransmitters from nerve endings nearby. The neuron then increases its internal potential, setting off a chain of events which is repeated for each Node of Ranvier as the nerve impulse "jumps" down the axon.

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Receptor

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a protein molecule, embedded in either the plasma membrane or the cytoplasm of a cell, to which one or more specific kinds of signaling molecules may attach. A molecule which binds (attaches) to a receptor is called a ligand, and may be a peptide (short protein) or other small molecule, such as a neurotransmitter, a hormone, a pharmaceutical drug, or a toxin. Each kind of receptor can bind only certain ligand shapes. Each cell typically has many receptors, of many different kinds.

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Receptor Potential

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a type of graded potential, is the transmembrane potential difference of a sensory receptor. A receptor potential is often produced by sensory transduction. It is generally a depolarizing event resulting from inward current flow. The influx of current will often bring the membrane potential of the sensory receptor towards the threshold for triggering an action potential. A receptor potential is a form of graded potential. An example of this is in a taste bud, where taste is converted into an electrical signal sent to the brain. When stimulated the taste bud triggers the release of neurotransmitter through exocytosis of synaptic vesicles from the presynaptic membrane. The neurotransmitter molecules diffuse across the synaptic cleft to the postsynaptic membrane.

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Refractory Period

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a period of time during which an organ or cell is incapable of repeating a particular action, or (more precisely) the amount of time it takes for an excitable membrane to be ready for a second stimulus once it returns to its resting state following an excitation. It most commonly refers to electrically excitable muscle cells or neurons.

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Resting Membrane Potential

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The relatively static membrane potential of quiescent cells is called the resting membrane potential (or resting voltage), as opposed to the specific dynamic electrochemical phenomena called action potential and graded membrane potential.

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Saltatory Conduction

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the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials without needing to increase the diameter of an axon.

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Second Messenger

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molecules that relay signals from receptors on the cell surface to target molecules inside the cell, in the cytoplasm or nucleus. They relay the signals of hormones like epinephrine (adrenalin), growth factors, and others, and cause some kind of change in the activity of the cell. They greatly amplify the strength of the signal.[1][2] Secondary messengers are a component of signal transduction cascades.

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Soma

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the bulbous end of a neuron, containing the cell nucleus. The word "soma" comes from the Greek σῶμα, meaning "body"; the soma of a neuron is often called the "cell body". There are many different specialized types of neurons, and their sizes vary from as small as about 30 micrometres to over 10 millimetre for some of the largest neurons of invertebrates.

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Spike-Triggering Zone

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where there are a lot of sodium channels. One the trigger zone is 'triggered' to threshold (from -70mV to -55mv), then an action potential occurs. Trigger zone is MOTOR neurons are in the axon hillock and in SENSORY neurons, they're in the 1st unmyelinated (first node of ranvier).

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Spine

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In human anatomy, the vertebral column (backbone or spine) is a column usually consisting of 33 vertebrae,[1] the sacrum, intervertebral discs, and the coccyx situated in the dorsal aspect of the torso, separated by spinal discs. It houses and protects the spinal cord in its spinal canal.

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Synapse

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a junction that permits a neuron to pass an electrical or chemical signal to another cell. The word "synapse" comes from "synaptein", which Sir Charles Scott Sherrington and colleagues coined from the Greek "syn-" ("together") and "haptein" ("to clasp").

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Synaptic Potential

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an alteration in the membrane potential of a cell resulting from activation of a synaptic input. All animal cells maintain a voltage difference between the intracellular and extracellular regions, holding the intracellular region at a negative voltage that in a baseline state is usually in the range -30 to -70 millivolts. Synaptic inputs from neurons can alter this voltage difference. If the intracellular voltage rises, the signal is called an excitatory postsynaptic potential (EPSP); if it falls the signal is called an inhibitory postsynaptic potential (IPSP). If the cell is electrically excitable, a sufficiently large EPSP may cause it to generate an action potential.

Front 38

Threshold

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the membrane potential to which a membrane must be depolarized to initiate an action potential.

It often can be between −40 and -55 mV, but it can vary based upon several factors. If ion channels are available, that will move the potential in the direction of the equilibrium potential for that ion.

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Vesicle

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store various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagating nerve impulses between neurons and are constantly recreated by the cell. The area in the axon which holds groups of vesicles is an axon terminal or "bouton". Up to 130 vesicles can be released per bouton over a ten minute period of stimulation at 0.2 Hz.[1] In the human brain region V1 synaptic vesicles have an average diameter of 39.5 nanometers with a standard deviation of 5.1 nanometers. [2]

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Amygdala

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are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans.[2] Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.[3].

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Association Cortex

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Any of the expanses of the cerebral cortex that are not sensory or motor in the customary sense, but instead are associated with advanced stages of sensory information processing, multisensory integration, or sensorimotor integration. Also called association area.

Front 42

Autonomic Nervous System

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part of the peripheral nervous system that acts as a control system functioning largely below the level of consciousness, and controls visceral functions.[1] The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition (urination), and sexual arousal. Whereas most of its actions are involuntary, some, such as breathing, work in tandem with the conscious mind.

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Basal Ganglia

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a group of nuclei in the brains of vertebrates. They are situated at the base of the forebrain and strongly connected with the cerebral cortex, thalamus and other areas. The basal ganglia are associated with a variety of functions, including motor control and learning. Currently popular theories implicate the basal ganglia primarily in action selection, that is, the decision of which of several possible behaviors to execute at a given time. Experimental studies show that the basal ganglia exert an inhibitory influence on a number of motor systems, and that a release of this inhibition permits a motor system to become active. The "behavior switching" that takes place within the basal ganglia is influenced by signals from many parts of the brain, including the prefrontal cortex, which is widely believed to play a key role in executive functions.

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Brainstem

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the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves. Though small, this is an extremely important part of the brain as the nerve connections of the motor and sensory systems from the main part of the brain to the rest of the body pass through the brain stem. This includes the corticospinal tract (motor), the posterior column-medial lemniscus pathway (fine touch, vibration sensation and proprioception) and the spinothalamic tract (pain, temperature, itch and crude touch). The brain stem also plays an important role in the regulation of cardiac and respiratory function. It also regulates the central nervous system, and is pivotal in maintaining consciousness and regulating the sleep cycle.

It is usually described as including the medulla oblongata (myelencephalon), pons (part of metencephalon), and midbrain (mesencephalon).[1][2] Less frequently, parts of the diencephalon are included.

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Central Nervous System (CNS)

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The central nervous system is that part of the nervous system that consists of the brain and spinal cord.
The central nervous system (CNS) is one of the two major divisions of the nervous system. The other is the peripheral nervous system (PNS) which is outside the brain and spinal cord.

The peripheral nervous system (PNS) connects the central nervous system (CNS) to sensory organs (such as the eye and ear), other organs of the body, muscles, blood vessels and glands. The peripheral nerves include the 12 cranial nerves, the spinal nerves and roots, and what are called the autonomic nerves that are concerned specifically with the regulation of the heart muscle, the muscles in blood vessel walls, and glands.

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Cerebellum

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The cerebellum is involved in the coordination of voluntary motor movement, balance and equilibrium and muscle tone. It is located just above the brain stem and toward the back of the brain. It is relatively well protected from trauma compared to the frontal and temporal lobes and brain stem.

Cerebellar injury results in movements that are slow and uncoordinated. Individuals with cerebellar lesions tend to sway and stagger when walking. Damage to the cerebellum can lead to: 1) loss of coordination of motor movement (asynergia), 2) the inability to judge distance and when to stop (dysmetria), 3) the inability to perform rapid alternating movements (adiadochokinesia), 4) movement tremors (intention tremor), 5) staggering, wide based walking (ataxic gait), 6) tendency toward falling, 7) weak muscles (hypotonia), 8) slurred speech (ataxic dysarthria), and 9) abnormal eye movements (nystagmus).

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Cerebral Cortex

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a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different composition in terms of neurons and connectivity. The human cerebral cortex is 2–4 mm (0.08–0.16 inches) thick.

In preserved brains, it has a gray color, hence the name "gray matter". In contrast to gray matter that is formed from neurons and their unmyelinated fibers, the white matter below them is formed predominantly by myelinated axons interconnecting neurons in different regions of the cerebral cortex with each other and neurons in other parts of the central nervous system.

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Commissure

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the place where two things are joined. The term is used especially in the fields of anatomy and biology.

In anatomy, commissure refers to a bundle of nerve fibers that cross the midline at their level of origin or entry (as opposed to a decussation of fibers that cross obliquely). The most common usage of the term refers to the brain's commissures, of which there are three—the anterior commissure, posterior commissure, and corpus callosum—and which consist of fibre tracts that connect the two cerebral hemispheres and span the longitudinal fissure. In the spinal cord is found the anterior white commissure. The term may also refer to the junction of the upper and lower lips, or of the upper and lower eyelids. In female genitalia, the joining points of the two folds of the labia major create two commissures - the anterior commissure just anterior to the prepuse of the clitoris, and the posterior commissure of the labia majora, directly posterior to the fenulum of the labia minora and anterior to the perineal raphe.

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Corpus Callosum

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known as the colossal commissure, is a wide, flat bundle of neural fibers beneath the cortex in the eutherian brain at the longitudinal fissure. It connects the left and right cerebral hemispheres and facilitates interhemispheric communication. It is the largest white matter structure in the brain, consisting of 200–250 million contralateral axonal projections.

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Corticogenesis

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The organization of cells during the development of the cortex of the brain

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Cytoarchitectonic Map

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Map of the structure of neurons within the brain- created by Broddman.

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Dura Mater

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the outermost of the three layers of the meninges surrounding the brain and spinal cord. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for keeping in the cerebrospinal fluid. The name "dura mater" is derived from the Latin "hard mother",[1] and is also referred to by the term "pachymeninx" (plural "pachymeninges").[2] The dura has been described as "tough and inflexible" and "leather-like".[2]

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Ectoderm

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the outer layer of the early embryo. It emerges first and forms from the outer layer of germ cells.

Generally speaking, the ectoderm differentiates to form the nervous system, tooth enamel and the epidermis (the outer part of integument).

In vertebrates, the ectoderm has three parts: external ectoderm (also known as surface ectoderm), the neural crest, and neural tube. The latter two are known as neuroectoderm.

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Frontal Lobe

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an area in the brain of humans and other mammals, located at the front of each cerebral hemisphere and positioned anterior to (in front of) the parietal lobes and above and anterior to the temporal lobes (i.e. directly behind the forehead or "temple"). It is separated from the parietal lobe by the post-central gyrus primary motor cortex, which controls voluntary movements of specific body parts associated with the precentral gyrus posteriorly, inferiorly by lateral sulcus[slyvian] which separates it from the temporal lobe, superiorly by the superior margin of the hemisphere and anteriorly by the frontal pole.

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Gray Matter

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a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and both unmyelinated axons and myelinated axons), glial cells (astroglia and oligodendrocytes) and capillaries. Grey matter contains neural cell bodies, in contrast to white matter, which does not and mostly contains myelinated axon tracts.[1] The color difference arises mainly from the whiteness of myelin. In living tissue, grey matter actually has a grey-brown color which comes from capillary blood vessels and neuronal cell bodies.

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Gyri

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is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci.

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Hippocampus

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a major component of the brains of humans and other mammals. It belongs to the limbic system and plays important roles in long-term memory and spatial navigation. Like the cerebral cortex, with which it is closely associated, it is a paired structure, with mirror-image halves in the left and right sides of the brain. In humans and other primates, the hippocampus is located inside the medial temporal lobe, beneath the cortical surface. It contains two main interlocking parts: Ammon's horn and the dentate gyrus.

In Alzheimer's disease the hippocampus is one of the first regions of the brain to suffer damage; memory problems and disorientation appear among the first symptoms. Damage to the hippocampus can also result from oxygen starvation (hypoxia), encephalitis, or medial temporal lobe epilepsy. People with extensive hippocampal damage may experience amnesia—the inability to form or retain new memories.

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Hypothalamus

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is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland (hypophysis). The hypothalamus is located below the thalamus, just above the brain stem. In the terminology of neuroanatomy, it forms the ventral part of the diencephalon. All vertebrate brains contain a hypothalamus. In humans, it is roughly the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system. It synthesizes and secretes certain neurohormones, often called hypothalamic-releasing hormones, and these in turn stimulate or inhibit the secretion of pituitary hormones. The hypothalamus controls body temperature, hunger, thirst,[1] fatigue, and circadian cycles.

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Limbic Sytem

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a set of brain structures including the hippocampus, amygdala, anterior thalamic nuclei, and limbic cortex, which seemingly support a variety of functions including emotion, behavior, long term memory, and olfaction.[1] The term "limbic" comes from the Latin limbus, for "border" or "edge". Some scientists have suggested that the concept of the limbic system should be abandoned as obsolete, as it is grounded more in transient tradition than in facts.[2]

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Medulla

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the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla. The medulla contains the cardiac, respiratory, vomiting and vasomotor centers and deals with autonomic functions, such as breathing, heart rate and blood pressure.

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Midbrain

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comprises the tectum (or corpora quadrigemina), tegmentum, the ventricular mesocoelia (or "iter"), and the cerebral peduncles, as well as several nuclei and fasciculi. Caudally the mesencephalon adjoins the pons (metencephalon) and rostrally it adjoins the diencephalon (Thalamus, hypothalamus, et al.).

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Neocortex

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called the neopallium ("new mantel") and isocortex ("equal rind"), is a part of the brain of mammals. It is the outer layer of the cerebral hemispheres, and made up of six layers, labelled I to VI (with VI being the innermost and I being the outermost). The neocortex is part of the cerebral cortex (along with the archicortex and paleocortex, which are cortical parts of the limbic system). It is involved in higher functions such as sensory perception, generation of motor commands, spatial reasoning, conscious thought and language.

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Neuronal Migration

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Neuronal migration is the method by which neurons travel from their origin or birth place to their final position in the brain. There are several ways they can do this, e.g. by radial migration or tangential migration. (see time lapse sequences of radial migration (also known as glial guidance) and somal translocation.)[4]

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Nucleus

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Nucleus of a neuron is an oval shaped membrane-bound structure found in the soma or body of the neuron. It contains the nucleolus and chromosomes, necessary for the coded production of proteins within the cell. The nucleolus of the nucleus produces ribosomes. The genetic information of an organism is coded within the long strands of deoxyribonucleic acid (DNA) from which the chromosomes are made. DNA is composed of two long chains that are interconnected in a helical arrangement. The sub units of a chromosome (genes) when activated induce the production of messenger ribonucleic acid (mRNA). mRNA is a duplicate of the information contained in the gene. mRNA leaves the nucleus and attaches to a ribosome, where is serves as a template for the production of a protein molecule.

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Occipital Lobe

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the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex.[1] The primary visual cortex is Brodmann area 17, commonly called V1 (visual one). Human V1 is located on the medial side of the occipital lobe within the calcarine sulcus; the full extent of V1 often continues onto the posterior pole of the occipital lobe. V1 is often also called striate cortex because it can be identified by a large stripe of myelin, the Stria of Gennari. Visually driven regions outside V1 are called extrastriate cortex. There are many extrastriate regions, and these are specialized for different visual tasks, such as visuospatial processing, color discrimination and motion perception. The name derives from the overlying occipital bone, which is named from the Latin oc- + caput, "back of the head".

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Parietal Lobe

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a lobe in the brain. It is positioned above (superior to) the occipital lobe and behind (posterior to) the frontal lobe.

The parietal lobe integrates sensory information from different modalities, particularly determining spatial sense and navigation. For example, it comprises somatosensory cortex and the dorsal stream of the visual system. This enables regions of the parietal cortex to map objects perceived visually into body coordinate positions. The name derives from the overlying parietal bone, which is named from the Latin pariet-, wall.

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Plastic

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known as cortical re-mapping) refers to the ability of the human brain to change as a result of one's experience, that the brain is 'plastic' and 'malleable'. The discovery of this feature of the brain is rather modern; the previous belief amongst scientists was that the brain does not change after the critical period of infancy.[1]

The brain consists of nerve cells (or "neurons") and glial cells which are interconnected, and learning may happen through change in the strength of the connections, by adding or removing connections, and by the formation of new cells. "Plasticity" relates to learning by adding or removing connections, or adding cells.

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Pons

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a structure located on the brain stem. It is superior to (up from) the medulla oblongata, inferior to (down from) the midbrain, and ventral to (in front of) the cerebellum. In humans and other bipeds this means it is above the medulla, below the midbrain, and anterior to the cerebellum. Its white matter includes tracts that conduct signals from the cerebrum down to the cerebellum and medulla, and tracts that carry the sensory signals up into the thalamus.[1]

The pons measures about 2.5 cm in length. Most of it appears as a broad anterior bulge rostral to the medulla. Posteriorly, it consists mainly of two pairs of thick stalks called cerebellar peduncles. They connect the cerebellum to the pons and midbrain. [2]

The pons contains nuclei that relay signals from the cerebrum to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.[3]

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Precursor Cells

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a type of partially differentiated, usually unipotent cell that has lost most or all of the stem cell multipotency.

Usually precursor cells are cells capable of differentiating into one or two closely related final forms. Sometimes precursor cell is used as an alternative term for multipotent stem cells.

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Prefrontal Cortex

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PFC) is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.

This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior.[1] The basic activity of this brain region is considered to be orchestration of thoughts and actions in accordance with internal goals.[2]

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Radial Glial Cell

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a pivotal cell type in the developing central nervous system (CNS) involved in key developmental processes, from patterning and neuronal migration to their recently discovered role as precursors during neurogenesis.[2][3][4] They arise early in development from neuroepithelial cells. Radial phenotype is typically transient, but some cells, such as Bergmann glia in the cerebellum and Muller glia in the retina, retain radial glia-like morphology postnatally. According to recent research, during the late stages of cortical development, radial glial cells divide asymmetrically in the ventricular zone to generate radial glial cells, postmitotic neurons and intermediate progenitor cells. Intermediate progenitor cells then divide symmetrically in the subventricular zone to generate neurons. During gliogenesis, radial glial cells differentiate into astrocytes.[5][6][7]

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Somatotopy

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The correspondence of receptors in regions or parts of the body via respective nerve fibers to specific functional areas of the cerebral cortex.

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Sulci

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a depression or fissure in the surface of the brain. It surrounds the gyri, creating the characteristic appearance of the brain in humans and other large mammals.

Large furrows (sulci) that divide the brain into lobes are often called fissures. The large furrow that divides the two hemispheres—the interhemispheric fissure—is very rarely called a "sulcus".

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Sylvian Fissure

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a fissure extending laterally between the temporal and frontal lobes, and turning posteriorly between the temporal and parietal lobes. Called also fissure of Sylvius, lateral cerebral sulcus.

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Temporal Lobe

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a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain.

The temporal lobe is involved in auditory perception and is home to the primary auditory cortex. It is also important for the processing of semantics in both speech and vision. The temporal lobe contains the hippocampus and plays a key role in the formation of long-term memory.

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Synaptogenesis

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the formation of synapses. Although it occurs throughout a healthy person's lifespan, an explosion of synapse formation occurs during early brain development. Synaptogenesis is particularly important during an individual's "critical period" of life, during which there is a certain degree of neuronal pruning due to competition for neural growth factors by neurons and synapses. Processes that are not used, or inhibited during this critical period will fail to develop normally later on in life.[1] Currently, the neuromuscular junction is the most well-characterized synapse, however new techniques have allowed for the study of hippocampal and cerebellar synapses.

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Thalamus

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a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections. Its function includes relaying sensation, spatial sense and motor signals to the cerebral cortex, along with the regulation of consciousness, sleep and alertness. The thalamus surrounds the third ventricle. It is the main product of the embryonic diencephalon.

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Topography

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is the study of Earth's surface shape and features or those of planets, moons, and asteroids. It is also the description of such surface shapes and features (especially their depiction in maps).

The topography of an area can also mean the surface shape and features themselves.

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Tract

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A neural pathway, or neural tract, connects one part of the nervous system with another and usually consists of bundles of elongated, myelin-insulated neurons, known collectively as white matter. Neural pathways serve to connect relatively distant areas of the brain or nervous system, compared to the local communication of grey matter.

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White Matter

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one of the two components of the central nervous system and consists mostly of myelinated axons. White matter tissue of the freshly cut brain appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color is due to its usual preservation in formaldehyde. A 20 year-old male has around 176,000 km of myelinated axons in his brain.[1]

The other main component of the brain is grey matter (actually pinkish tan due to blood capillaries). A third colored component found in the brain that appears darker due to higher levels of melanin in dopaminergic neurons than its nearby areas is the substantia nigra.

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Angiography

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a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins and the heart chambers. This is traditionally done by injecting a radio-opaque contrast agent into the blood vessel and imaging using X-ray based techniques such as fluoroscopy. The word itself comes from the Greek words angeion, "vessel", and graphein, "to write or record". The film or image of the blood vessels is called an angiograph, or more commonly, an angiogram.

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Blood Oxygenation Level-Dependant (BOLD)

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Blood-oxygen-level dependent (BOLD) magnetic resonance imaging (MRI) is technique useful in detecting myocardial ischemia. Oxyhaemoglobin and deoxyhaemoglobin differ in their magnetic properties – the former in diamagnetic while the latter is paramagnetic. This difference in magnetic properties can be used as an endogenous contrast to visualize tissue oxygenation. This technique has been termed BOLD MRI. Deoxygenation of hemoglobin causes inhomogeneity in the local magnetic field and hence a change in T2 weighted MRI images. BOLD MRI can detect changes in deoxyhemoglobin levels as a result of changes in blood flow and oxygen consumption. When coronary vasodilation is induced by giving dipyridamole, the levels of deoxyhemoglobin in the coronary venous blood falls as the blood flow increase is disproportionate to the oxygen demand. Occlusion of a coronary artery on the other hand increases the myocardial venous blood deoxyhemoglobin concentration due to myocardial ischemia. In areas supplied by a stenotic coronary artery, there will be no vasodilatory reserve as the capillaries are already maximally dilated. Hence dipyridamole can be used to identify ischemic myocardium by BOLD MRI as these regions will show decreased signal on MRI suggesting hypoperfusion.

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Brain Lesion

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any abnormal tissue found on or in an organism, usually damaged by disease or trauma. Lesion is derived from the Latin word laesio which means injury.

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Cognitive Psychology

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a subdiscipline of psychology exploring internal mental processes. It is the study of how people perceive, remember, think, speak, and solve problems.[1]

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Computed Tomography (CT, CAT)

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a medical imaging method employing tomography created by computer processing.[1] Digital geometry processing is used to generate a three-dimensional image of the inside of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation.[2]

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Deep-Brain Stimulation (DBS)

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a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain. DBS in select brain regions has provided remarkable therapeutic benefits for otherwise treatment-resistant movement and affective disorders such as chronic pain, Parkinson's disease, tremor and dystonia.[1] Despite the long history of DBS,[2] its underlying principles and mechanisms are still not clear. DBS directly changes brain activity in a controlled manner, its effects are reversible (unlike those of lesioning techniques) and is one of only a few neurosurgical methods that allows blinded studies.

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Diffusion Tensor Imaging (DTI)

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is important when a tissue—such as the neural axons of white matter in the brain or muscle fibers in the heart—has an internal fibrous structure analogous to the anisotropy of some crystals. Water will then diffuse more rapidly in the direction aligned with the internal structure, and more slowly as it moves perpendicular to the preferred direction. This also means that the measured rate of diffusion will differ depending on the direction from which an observer is looking. In DTI, each voxel therefore has one or more pairs of parameters: a rate of diffusion and a preferred direction of diffusion—described in terms of three dimensional space—for which that parameter is valid. The properties of each voxel of a single DTI image is usually calculated by vector or tensor math from six or more different diffusion weighted acquisitions, each obtained with a different orientation of the diffusion sensitizing gradients. In some methods, hundreds of measurements—each making up a complete image—are made to generate a single resulting calculated image data set. The higher information content of a DTI voxel makes it extremely sensitive to subtle pathology in the brain. In addition the directional information can be exploited at a higher level of structure to select and follow neural tracts through the brain—a process called tractography.[1][2]

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Double Dissociation

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To strengthen a single dissociation, a researcher can establish a "double dissociation", a term that was introduced by H.-L. Teuber in 1955.[2] This is the demonstration that two experimental manipulations each have different effects on two dependent variables; if one manipulation affects the first variable and not the second, the other manipulation affects the second variable and not the first.[3] If one can demonstrate that a lesion in brain structure A impairs function X but not Y, and further demonstrate that a lesion to brain structure B impairs function Y but spares function X, one can make more specific inferences about brain function and function localization.

In cognitive neuroscience, double dissociation is an experimental technique by which two areas of neocortex are functionally dissociated by two behavioral tests, each test being affected by a lesion in one zone and not the other.[4] In a series of patients with traumatic brain injury, one might find two patients, A and B. Patient A has difficulty performing cognitive tests for, say auditory memory but has no problem with visual memory. Patient B has the opposite problem. By using neuroimaging (or neuropathology post-mortem) to identify the overlap and dissociation between lesioned areas of the brain, one can infer something about the localization of visual and auditory function in the normal brain.

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Electroencephalography (EEG)

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the recording of electrical activity along the scalp produced by the firing of neurons within the brain.[2] In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from multiple electrodes placed on the scalp. In neurology, the main diagnostic application of EEG is in the case of epilepsy, as epileptic activity can create clear abnormalities on a standard EEG study.[3] A secondary clinical use of EEG is in the diagnosis of coma, encephalopathies, and brain death. EEG used to be a first-line method for the diagnosis of tumors, stroke and other focal brain disorders, but this use has decreased with the advent of anatomical imaging techniques such as MRI and CT.

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Event-Related Potential (ERP)

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a form of functional Magnetic Resonance Imaging (fMRI) in which a series of fMRI images are time-locked to a stimulus presentation and averaged together over many trials. The relationship of the technique to fMRI is analogous to the relationship between Event-related potential (ERP) data and Electroencephalogram (EEG) data.

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Functional Magnetic Resonance Imaging (fMRI)

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a type of specialized MRI scan. It measures the hemodynamic response (change in blood flow) related to neural activity in the brain or spinal cord of humans or other animals. It is one of the most recently developed forms of neuroimaging. Since the early 1990s, fMRI has come to dominate the brain mapping field due to its relatively low invasiveness, absence of radiation exposure, and relatively wide availability.

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Knockout Procedure

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a genetically engineered mouse in which one or more genes have been turned off through a targeted mutation.

Knockout mice are important animal models for studying the role of genes which have been sequenced but whose functions have not been determined. By causing a specific gene to be inactive in the mouse, and observing any differences from normal behaviour or condition, researchers can infer its probable function.

Mice are currently the most closely related laboratory animal species to humans for which the knockout technique can easily be applied. They are widely used in knockout experiments, especially those investigating genetic questions that relate to human physiology. Gene knockout in rats is much harder and has only been possible since 2003.[1][2]

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Magnetic Resonance Imaging (MRI)

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primarily a noninvasive medical imaging technique used in radiology to visualize detailed internal structure and limited function of the body. MRI provides much greater contrast between the different soft tissues of the body than computed tomography (CT) does, making it especially useful in neurological (brain), musculoskeletal, cardiovascular, and oncological (cancer) imaging.

Unlike CT, MRI uses no ionizing radiation. Rather, it uses a powerful magnetic field to align the nuclear magnetization of (usually) hydrogen atoms in water in the body. Radio frequency (RF) fields are used to systematically alter the alignment of this magnetization. This causes the hydrogen nuclei to produce a rotating magnetic field detectable by the scanner. This signal can be manipulated by additional magnetic fields to build up enough information to construct an image of the body.[1]:36

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Magnetoencephalography (MEG)

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a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using arrays of SQUIDs (superconducting quantum interference devices). Applications of MEG include localizing regions affected by pathology before surgical removal, determining the function of various parts of the brain, and neurofeedback.

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Multiunit Recording

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the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart. In neuroscience, it includes measurements of the electrical activity of neurons, and particularly action potential activity. Recordings of large-scale electric signals from the nervous system such as electroencephalography, may also be referred to as electrophysiological recordings[1].

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Neural Network

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the term neural network had been used to refer to a network or circuit of biological neurons[1]; the modern usage of the term often refers to artificial neural networks, which are composed of artificial neurons or nodes.

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Neurology

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is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue, such as muscle.[1] The corresponding surgical specialty is neurosurgery. A neurologist is a physician who specializes in neurology, and is trained to investigate, or diagnose and treat neurological disorders. Pediatric neurologists treat neurological disease in children. Neurologists may also be involved in clinical research, clinical trials, as well as basic research and translational research.

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Neurophysiology

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is a part of physiology. Neurophysiology is the study of nervous system function. Primarily, it is connected with neurobiology, psychology, neurology, clinical neurophysiology, electrophysiology, biophysical neurophysiology, ethology, neuroanatomy, cognitive science and other brain sciences.[1]
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Positron Emission Tomography (PET)

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a nuclear medicine imaging technique which produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule. Images of tracer concentration in 3-dimensional or 4-dimensional space (the 4th dimension being time) within the body are then reconstructed by computer analysis. In modern scanners, this reconstruction is often accomplished with the aid of a CT X-ray scan performed on the patient during the same session, in the same machine.

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Receptive Field

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The receptive field of a sensory neuron is a region of space in which the presence of a stimulus will alter the firing of that neuron. Receptive fields have been identified for neurons of the auditory system, the somatosensory system, and the visual system.

The concept of receptive fields can be extended to further up the neural system; if many sensory receptors all form synapses with a single cell further up, they collectively form the receptive field of that cell. For example, the receptive field of a ganglion cell in the retina of the eye is composed of input from all of the photoreceptors which synapse with it, and a group of ganglion cells in turn forms the receptive field for a cell in the brain. This process is called convergence.

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Regional Cerebral Blood Flow (rCBF)

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analyzed in PET

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Retinotopic

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the spatial organization of the neuronal responses to visual stimuli. In many locations within the brain, adjacent neurons have receptive fields that include slightly different, but overlapping portions of the visual field. The position of the center of these receptive fields forms an orderly sampling mosaic that covers a portion of the visual field. Because of this orderly arrangement, which emerges from the spatial specificity of connections between neurons in different parts of the visual system, cells in each structure can be seen as forming a map of the visual field (also called a retinotopic map, or a visuotopic map). Retinotopic maps are a particular case of topographic organization. Many brain structures that are responsive to visual input, including much of the visual cortex and visual nuclei of the brain stem (such as the superior colliculus) and thalamus (such as the lateral geniculate nucleus and the pulvinar), are organized into retinotopic maps, also called visual field maps.

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Voxel

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{a statistical technique for examining differences in brain activity recorded during functional neuroimaging experiments using neuroimaging technologies such as fMRI or PET. It may also refer to a specific piece of software created by the Wellcome Department of Imaging Neuroscience (part of University College London) to carry out such analyses.}

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Single-Cell Recording

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a technique used in research to observe changes in voltage or current in a neuron.

In this technique an animal, usually anesthetized, has a microelectrode inserted into its skull and into a neuron in the area of the brain that is of interest. The electrode measures the changes in charge as the neuron reaches its action potential.

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Single Dissociation

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When dissecting complex mental tasks into their subcomponents, a researcher can establish a "single dissociation" between functions. This is done by demonstrating that a lesion to brain structure A disrupts function X but not function Y. Such a demonstration allows one to infer that function X and function Y are independent of each other in some way.

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Transcranial magnetic Stimulation (TMS)

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a noninvasive method to cause depolarization in the neurons of the brain. TMS uses electromagnetic induction to induce weak electric currents using a rapidly changing magnetic field; this can cause activity in specific or general parts of the brain with minimal discomfort, allowing the functioning and interconnections of the brain to be studied. A variant of TMS, repetitive transcranial magnetic stimulation (rTMS), has been tested as a treatment tool for various neurological and psychiatric disorders including migraines, strokes, Parkinson's disease, dystonia, tinnitus, depression and auditory hallucinations.