Extinction, Psychological: The procedure of presenting the conditioned stimulus without REINFORCEMENT to an organism previously conditioned. It refers also to the diminution of a conditioned response resulting from this procedure.Extinction, Biological: The ceasing of existence of a species or taxonomic groups of organisms.Fear: The affective response to an actual current external danger which subsides with the elimination of the threatening condition.Conditioning, Classical: Learning that takes place when a conditioned stimulus is paired with an unconditioned stimulus.Freezing Reaction, Cataleptic: An induced response to threatening stimuli characterized by the cessation of body movements, except for those that are involved with BREATHING, and the maintenance of an immobile POSTURE.Conditioning (Psychology): A general term referring to the learning of some particular response.Cycloserine: Antibiotic substance produced by Streptomyces garyphalus.Fossils: Remains, impressions, or traces of animals or plants of past geological times which have been preserved in the earth's crust.Conditioning, Operant: Learning situations in which the sequence responses of the subject are instrumental in producing reinforcement. When the correct response occurs, which involves the selection from among a repertoire of responses, the subject is immediately reinforced.Paleontology: The study of early forms of life through fossil remains.Amygdala: Almond-shaped group of basal nuclei anterior to the INFERIOR HORN OF THE LATERAL VENTRICLE of the TEMPORAL LOBE. The amygdala is part of the limbic system.Electroshock: Induction of a stress reaction in experimental subjects by means of an electrical shock; applies to either convulsive or non-convulsive states.Association Learning: The principle that items experienced together enter into a connection, so that one tends to reinstate the other.Population Dynamics: The pattern of any process, or the interrelationship of phenomena, which affects growth or change within a population.Conservation of Natural Resources: The protection, preservation, restoration, and rational use of all resources in the total environment.Reinforcement (Psychology): The strengthening of a conditioned response.Ecosystem: A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)Biodiversity: The variety of all native living organisms and their various forms and interrelationships.Self Administration: Administration of a drug or chemical by the individual under the direction of a physician. It includes administration clinically or experimentally, by human or animal.Avoidance Learning: A response to a cue that is instrumental in avoiding a noxious experience.Drug-Seeking Behavior: Activities performed to obtain licit or illicit substances.Behavior, Animal: The observable response an animal makes to any situation.Galvanic Skin Response: A change in electrical resistance of the skin, occurring in emotion and in certain other conditions.Cues: Signals for an action; that specific portion of a perceptual field or pattern of stimuli to which a subject has learned to respond.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.Endangered Species: An animal or plant species in danger of extinction. Causes can include human activity, changing climate, or change in predator/prey ratios.Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Reinforcement Schedule: A schedule prescribing when the subject is to be reinforced or rewarded in terms of temporal interval in psychological experiments. The schedule may be continuous or intermittent.Cocaine: An alkaloid ester extracted from the leaves of plants including coca. It is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake.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.History, Ancient: The period of history before 500 of the common era.Appetitive Behavior: Animal searching behavior. The variable introductory phase of an instinctive behavior pattern or sequence, e.g., looking for food, or sequential courtship patterns prior to mating.Rats, Long-Evans: An outbred strain of rats developed in 1915 by crossing several Wistar Institute white females with a wild gray male. Inbred strains have been derived from this original outbred strain, including Long-Evans cinnamon rats (RATS, INBRED LEC) and Otsuka-Long-Evans-Tokushima Fatty rats (RATS, INBRED OLETF), which are models for Wilson's disease and non-insulin dependent diabetes mellitus, respectively.Behavior, Addictive: The observable, measurable, and often pathological activity of an organism that portrays its inability to overcome a habit resulting in an insatiable craving for a substance or for performing certain acts. The addictive behavior includes the emotional and physical overdependence on the object of habit in increasing amount or frequency.Population Density: Number of individuals in a population relative to space.Birds: Warm-blooded VERTEBRATES possessing FEATHERS and belonging to the class Aves.Geography: The science dealing with the earth and its life, especially the description of land, sea, and air and the distribution of plant and animal life, including humanity and human industries with reference to the mutual relations of these elements. (From Webster, 3d ed)Startle Reaction: A complex involuntary response to an unexpected strong stimulus usually auditory in nature.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.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.Human Activities: Activities performed by humans.Retention (Psychology): The persistence to perform a learned behavior (facts or experiences) after an interval has elapsed in which there has been no performance or practice of the behavior.Dopamine Uptake Inhibitors: Drugs that block the transport of DOPAMINE into axon terminals or into storage vesicles within terminals. Most of the ADRENERGIC UPTAKE INHIBITORS also inhibit dopamine uptake.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Mental Recall: The process whereby a representation of past experience is elicited.Marine Biology: The study of the origin, structure, development, growth, function, genetics, and reproduction of organisms which inhabit the OCEANS AND SEAS.Volcanic Eruptions: The ash, dust, gases, and lava released by volcanic explosion. The gases are volatile matter composed principally of about 90% water vapor, and carbon dioxide, sulfur dioxide, hydrogen, carbon monoxide, and nitrogen. The ash or dust is pyroclastic ejecta and lava is molten extrusive material consisting mainly of magnesium silicate. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Acoustic Stimulation: Use of sound to elicit a response in the nervous system.Ecology: The branch of science concerned with the interrelationship of organisms and their ENVIRONMENT, especially as manifested by natural cycles and rhythms, community development and structure, interactions between different kinds of organisms, geographic distributions, and population alterations. (Webster's, 3d ed)Amphibians: VERTEBRATES belonging to the class amphibia such as frogs, toads, newts and salamanders that live in a semiaquatic environment.Environment: The external elements and conditions which surround, influence, and affect the life and development of an organism or population.Cocaine-Related Disorders: Disorders related or resulting from use of cocaine.Mammals: Warm-blooded vertebrate animals belonging to the class Mammalia, including all that possess hair and suckle their young.Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Geology: The science of the earth and other celestial bodies and their history as recorded in the rocks. It includes the study of geologic processes of an area such as rock formations, weathering and erosion, and sedimentation. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Antimetabolites: Drugs that are chemically similar to naturally occurring metabolites, but differ enough to interfere with normal metabolic pathways. (From AMA Drug Evaluations Annual, 1994, p2033)Geological Phenomena: The inanimate matter of Earth, the structures and properties of this matter, and the processes that affect it.Learning: Relatively permanent change in behavior that is the result of past experience or practice. The concept includes the acquisition of knowledge.Chytridiomycota: A phylum of fungi that was formerly considered a subdivision of Phycomycetes. They are the only fungi that produce motile spores (zoospores) at some stage in their life cycle. Most are saprobes but they also include examples of plant, animal, and fungal pathogens.Climate Change: Any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer). It may result from natural factors such as changes in the sun's intensity, natural processes within the climate system such as changes in ocean circulation, or human activities.Columbidae: Family in the order COLUMBIFORMES, comprised of pigeons or doves. They are BIRDS with short legs, stout bodies, small heads, and slender bills. Some sources call the smaller species doves and the larger pigeons, but the names are interchangeable.Food Chain: The sequence of transfers of matter and energy from organism to organism in the form of FOOD. Food chains intertwine locally into a food web because most organisms consume more than one type of animal or plant. PLANTS, which convert SOLAR ENERGY to food by PHOTOSYNTHESIS, are the primary food source. In a predator chain, a plant-eating animal is eaten by a larger animal. In a parasite chain, a smaller organism consumes part of a larger host and may itself be parasitized by smaller organisms. In a saprophytic chain, microorganisms live on dead organic matter.Muscimol: A neurotoxic isoxazole isolated from species of AMANITA. It is obtained by decarboxylation of IBOTENIC ACID. Muscimol is a potent agonist of GABA-A RECEPTORS and is used mainly as an experimental tool in animal and tissue studies.Cephalopoda: A class in the phylum MOLLUSCA comprised of SQUID; CUTTLEFISH; OCTOPUS; and NAUTILUS. These marine animals are the most highly organized of all the mollusks.Radiometric Dating: Techniques used to determine the age of materials, based on the content and half-lives of the RADIOACTIVE ISOTOPES they contain.Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Discrimination Learning: Learning that is manifested in the ability to respond differentially to various stimuli.Carnivora: An order of MAMMALS, usually flesh eaters with appropriate dentition. Suborders include the terrestrial carnivores Fissipedia, and the aquatic carnivores PINNIPEDIA.Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Limbic System: A set of forebrain structures common to all mammals that is defined functionally and anatomically. It is implicated in the higher integration of visceral, olfactory, and somatic information as well as homeostatic responses including fundamental survival behaviors (feeding, mating, emotion). For most authors, it includes the AMYGDALA; EPITHALAMUS; GYRUS CINGULI; hippocampal formation (see HIPPOCAMPUS); HYPOTHALAMUS; PARAHIPPOCAMPAL GYRUS; SEPTAL NUCLEI; anterior nuclear group of thalamus, and portions of the basal ganglia. (Parent, Carpenter's Human Neuroanatomy, 9th ed, p744; NeuroNames, http://rprcsgi.rprc.washington.edu/neuronames/index.html (September 2, 1998)).Implosive Therapy: A method for extinguishing anxiety by a saturation exposure to the feared stimulus situation or its substitute.Self-Injurious Behavior: Behavior in which persons hurt or harm themselves without the motive of suicide or of sexual deviation.Reptiles: Cold-blooded, air-breathing VERTEBRATES belonging to the class Reptilia, usually covered with external scales or bony plates.Escape Reaction: Innate response elicited by sensory stimuli associated with a threatening situation, or actual confrontation with an enemy.Invertebrates: Animals that have no spinal column.Foraminifera: An order of amoeboid EUKARYOTES characterized by reticulating pseudopods and a complex life cycle with an alternation of generations. Most are less than 1mm in size and found in marine or brackish water.Reward: An object or a situation that can serve to reinforce a response, to satisfy a motive, or to afford pleasure.Climate: The longterm manifestations of WEATHER. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Genetic Speciation: The splitting of an ancestral species into daughter species that coexist in time (King, Dictionary of Genetics, 6th ed). Causal factors may include geographic isolation, HABITAT geometry, migration, REPRODUCTIVE ISOLATION, random GENETIC DRIFT and MUTATION.Anisomycin: An antibiotic isolated from various Streptomyces species. It interferes with protein and DNA synthesis by inhibiting peptidyl transferase or the 80S ribosome system.Oxepins: Compounds based on a 7-membered heterocyclic ring including an oxygen. They can be considered a medium ring ether. A natural source is the MONTANOA plant genus. Some dibenzo-dioxepins, called depsidones, are found in GARCINIA plants.Mediodorsal Thalamic Nucleus: The largest of the medial nuclei of the thalamus. It makes extensive connections with most of the other thalamic nuclei.Feeding and Eating Disorders of Childhood: Mental disorders related to feeding and eating usually diagnosed in infancy or early childhood.PhenoxyacetatesNucleus 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.Generalization, Stimulus: The tendency to react to stimuli that are different from, but somewhat similar to, the stimulus used as a conditioned stimulus.Heroin: A narcotic analgesic that may be habit-forming. It is a controlled substance (opium derivative) listed in the U.S. Code of Federal Regulations, Title 21 Parts 329.1, 1308.11 (1987). Sale is forbidden in the United States by Federal statute. (Merck Index, 11th ed)Archaeology: The scientific study of past societies through artifacts, fossils, etc.Perceptual Disorders: Cognitive disorders characterized by an impaired ability to perceive the nature of objects or concepts through use of the sense organs. These include spatial neglect syndromes, where an individual does not attend to visual, auditory, or sensory stimuli presented from one side of the body.Behavior Therapy: The application of modern theories of learning and conditioning in the treatment of behavior disorders.Predatory Behavior: Instinctual behavior pattern in which food is obtained by killing and consuming other species.Time: The dimension of the physical universe which, at a given place, orders the sequence of events. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Trees: Woody, usually tall, perennial higher plants (Angiosperms, Gymnosperms, and some Pterophyta) having usually a main stem and numerous branches.Genetic Load: The relative amount by which the average fitness of a POPULATION is lowered, due to the presence of GENES that decrease survival, compared to the GENOTYPE with maximum or optimal fitness. (From Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)Conditioning, Eyelid: Reflex closure of the eyelid occurring as a result of classical conditioning.Stochastic Processes: Processes that incorporate some element of randomness, used particularly to refer to a time series of random variables.Vertebrates: Animals having a vertebral column, members of the phylum Chordata, subphylum Craniata comprising mammals, birds, reptiles, amphibians, and fishes.Mammoths: An extinct genus of large mammals in the family Elephantidae that fed by grazing on low vegetation. Most died out at the end of the last ice age.Blinking: Brief closing of the eyelids by involuntary normal periodic closing, as a protective measure, or by voluntary action.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.Body Size: The physical measurements of a body.GABA Agonists: Endogenous compounds and drugs that bind to and activate GAMMA-AMINOBUTYRIC ACID receptors (RECEPTORS, GABA).Minor Planets: Small solar system planetary bodies including asteroids. Most asteroids are found within the gap lying between the orbits of Mars and Jupiter.ArtiodactylaOceans and Seas: A great expanse of continuous bodies of salt water which together cover more than 70 percent of the earth's surface. Seas may be partially or entirely enclosed by land, and are smaller than the five oceans (Atlantic, Pacific, Indian, Arctic, and Antarctic).Tropical Climate: A climate which is typical of equatorial and tropical regions, i.e., one with continually high temperatures with considerable precipitation, at least during part of the year. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Nootropic Agents: Drugs used to specifically facilitate learning or memory, particularly to prevent the cognitive deficits associated with dementias. These drugs act by a variety of mechanisms. While no potent nootropic drugs have yet been accepted for general use, several are being actively investigated.Taste: The ability to detect chemicals through gustatory receptors in the mouth, including those on the TONGUE; the PALATE; the PHARYNX; and the EPIGLOTTIS.Generalization (Psychology): The phenomenon of an organism's responding to all situations similar to one in which it has been conditioned.Greenhouse Effect: The effect of GLOBAL WARMING and the resulting increase in world temperatures. The predicted health effects of such long-term climatic change include increased incidence of respiratory, water-borne, and vector-borne diseases.Dinosaurs: General name for two extinct orders of reptiles from the Mesozoic era: Saurischia and Ornithischia.North AmericaFeeding Behavior: Behavioral responses or sequences associated with eating including modes of feeding, rhythmic patterns of eating, and time intervals.Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.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.Proto-Oncogene Proteins c-fos: Cellular DNA-binding proteins encoded by the c-fos genes (GENES, FOS). They are involved in growth-related transcriptional control. c-fos combines with c-jun (PROTO-ONCOGENE PROTEINS C-JUN) to form a c-fos/c-jun heterodimer (TRANSCRIPTION FACTOR AP-1) that binds to the TRE (TPA-responsive element) in promoters of certain genes.Aquatic Organisms: Organisms that live in water.Protein Synthesis Inhibitors: Compounds which inhibit the synthesis of proteins. They are usually ANTI-BACTERIAL AGENTS or toxins. Mechanism of the action of inhibition includes the interruption of peptide-chain elongation, the blocking the A site of ribosomes, the misreading of the genetic code or the prevention of the attachment of oligosaccharide side chains to glycoproteins.Lithium Chloride: A salt of lithium that has been used experimentally as an immunomodulator.Intellectual Disability: Subnormal intellectual functioning which originates during the developmental period. This has multiple potential etiologies, including genetic defects and perinatal insults. Intelligence quotient (IQ) scores are commonly used to determine whether an individual has an intellectual disability. IQ scores between 70 and 79 are in the borderline range. Scores below 67 are in the disabled range. (from Joynt, Clinical Neurology, 1992, Ch55, p28)Overlearning: Learning in which practice proceeds beyond the point where the act can just be performed with the required degree of excellence.Butterflies: Slender-bodies diurnal insects having large, broad wings often strikingly colored and patterned.Wolves: Any of several large carnivorous mammals of the family CANIDAE that usually hunt in packs.Mice, Inbred C57BLMicroinjections: The injection of very small amounts of fluid, often with the aid of a microscope and microsyringes.Regression (Psychology): A return to earlier, especially to infantile, patterns of thought or behavior, or stage of functioning, e.g., feelings of helplessness and dependency in a patient with a serious physical illness. (From APA, Thesaurus of Psychological Index Terms, 1994).Yohimbine: A plant alkaloid with alpha-2-adrenergic blocking activity. Yohimbine has been used as a mydriatic and in the treatment of ERECTILE DYSFUNCTION.Motivation: Those factors which cause an organism to behave or act in either a goal-seeking or satisfying manner. They may be influenced by physiological drives or by external stimuli.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.Geologic Sediments: A mass of organic or inorganic solid fragmented material, or the solid fragment itself, that comes from the weathering of rock and is carried by, suspended in, or dropped by air, water, or ice. It refers also to a mass that is accumulated by any other natural agent and that forms in layers on the earth's surface, such as sand, gravel, silt, mud, fill, or loess. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1689)Models, Theoretical: Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.Psychological Theory: Principles applied to the analysis and explanation of psychological or behavioral phenomena.Competitive Behavior: The direct struggle between individuals for environmental necessities or for a common goal.Anxiety Disorders: Persistent and disabling ANXIETY.Receptor, Cannabinoid, CB1: A subclass of cannabinoid receptor found primarily on central and peripheral NEURONS where it may play a role modulating NEUROTRANSMITTER release.Glycine Plasma Membrane Transport Proteins: A family of sodium chloride-dependent neurotransmitter symporters that transport the amino acid GLYCINE. They differ from GLYCINE RECEPTORS, which signal cellular responses to GLYCINE. They are located primarily on the PLASMA MEMBRANE of NEURONS; GLIAL CELLS; EPITHELIAL CELLS; and RED BLOOD CELLS where they remove inhibitory neurotransmitter glycine from the EXTRACELLULAR SPACE.Daphnia: A diverse genus of minute freshwater CRUSTACEA, of the suborder CLADOCERA. They are a major food source for both young and adult freshwater fish.Neuronal Plasticity: The capacity of the NERVOUS SYSTEM to change its reactivity as the result of successive activations.Desensitization, Psychologic: A behavior therapy technique in which deep muscle relaxation is used to inhibit the effects of graded anxiety-evoking stimuli.Inhibition (Psychology): The interference with or prevention of a behavioral or verbal response even though the stimulus for that response is present; in psychoanalysis the unconscious restraining of an instinctual process.Hybrid Cells: Any cell, other than a ZYGOTE, that contains elements (such as NUCLEI and CYTOPLASM) from two or more different cells, usually produced by artificial CELL FUSION.Meteoroids: Any solid objects moving in interplanetary space that are smaller than a planet or asteroid but larger than a molecule. Meteorites are any meteoroid that has fallen to a planetary surface. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Polynesia: The collective name for the islands of the central Pacific Ocean, including the Austral Islands, Cook Islands, Easter Island, HAWAII; NEW ZEALAND; Phoenix Islands, PITCAIRN ISLAND; SAMOA; TONGA; Tuamotu Archipelago, Wake Island, and Wallis and Futuna Islands. Polynesians are of the Caucasoid race, but many are of mixed origin. Polynesia is from the Greek poly, many + nesos, island, with reference to the many islands in the group. (From Webster's New Geographical Dictionary, 1988, p966 & Room, Brewer's Dictionary of Names, 1992, p426)Substance Withdrawal Syndrome: Physiological and psychological symptoms associated with withdrawal from the use of a drug after prolonged administration or habituation. The concept includes withdrawal from smoking or drinking, as well as withdrawal from an administered drug.Animal Migration: Periodic movements of animals in response to seasonal changes or reproductive instinct. Hormonal changes are the trigger in at least some animals. Most migrations are made for reasons of climatic change, feeding, or breeding.Ursidae: The family of carnivorous or omnivorous bears, having massive bodies, coarse heavy fur, relatively short limbs, and almost rudimentary tails.Bivalvia: A class in the phylum MOLLUSCA comprised of mussels; clams; OYSTERS; COCKLES; and SCALLOPS. They are characterized by a bilaterally symmetrical hinged shell and a muscular foot used for burrowing and anchoring.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)Biota: The spectrum of different living organisms inhabiting a particular region, habitat, or biotope.Habituation, Psychophysiologic: The disappearance of responsiveness to a repeated stimulation. It does not include drug habituation.Genetics, Population: The discipline studying genetic composition of populations and effects of factors such as GENETIC SELECTION, population size, MUTATION, migration, and GENETIC DRIFT on the frequencies of various GENOTYPES and PHENOTYPES using a variety of GENETIC TECHNIQUES.Genetic Variation: Genotypic differences observed among individuals in a population.Narcotics: Agents that induce NARCOSIS. Narcotics include agents that cause somnolence or induced sleep (STUPOR); natural or synthetic derivatives of OPIUM or MORPHINE or any substance that has such effects. They are potent inducers of ANALGESIA and OPIOID-RELATED DISORDERS.Immobility Response, Tonic: An induced response to threatening stimuli characterized by complete loss of muscle strength.Saccharin: Flavoring agent and non-nutritive sweetener.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Neural Pathways: Neural tracts connecting one part of the nervous system with another.Phylogeography: A field of study concerned with the principles and processes governing the geographic distributions of genealogical lineages, especially those within and among closely related species. (Avise, J.C., Phylogeography: The History and Formation of Species. Harvard University Press, 2000)Excitatory Amino Acid Antagonists: Drugs that bind to but do not activate excitatory amino acid receptors, thereby blocking the actions of agonists.Cannabinoid Receptor Agonists: Compounds that interact with and stimulate the activity of CANNABINOID RECEPTORS.Anthozoa: A class in the phylum CNIDARIA, comprised mostly of corals and anemones. All members occur only as polyps; the medusa stage is completely absent.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).Stress Disorders, Post-Traumatic: A class of traumatic stress disorders with symptoms that last more than one month. There are various forms of post-traumatic stress disorder, depending on the time of onset and the duration of these stress symptoms. In the acute form, the duration of the symptoms is between 1 to 3 months. In the chronic form, symptoms last more than 3 months. With delayed onset, symptoms develop more than 6 months after the traumatic event.Pacific OceanEcological and Environmental Processes: Ecosystem and environmental activities, functions, or events.Anxiety: Feeling or emotion of dread, apprehension, and impending disaster but not disabling as with ANXIETY DISORDERS.Pyrazoles: Azoles of two nitrogens at the 1,2 positions, next to each other, in contrast with IMIDAZOLES in which they are at the 1,3 positions.Population Growth: Increase, over a specific period of time, in the number of individuals living in a country or region.Memory, Long-Term: Remembrance of information from 3 or more years previously.Transfer (Psychology): Change in learning in one situation due to prior learning in another situation. The transfer can be positive (with second learning improved by first) or negative (where the reverse holds).Attention: Focusing on certain aspects of current experience to the exclusion of others. It is the act of heeding or taking notice or concentrating.Excitatory Amino Acid Agonists: Drugs that bind to and activate excitatory amino acid receptors.Learning Disorders: Conditions characterized by a significant discrepancy between an individual's perceived level of intellect and their ability to acquire new language and other cognitive skills. These disorders may result from organic or psychological conditions. Relatively common subtypes include DYSLEXIA, DYSCALCULIA, and DYSGRAPHIA.Uranium: Uranium. A radioactive element of the actinide series of metals. It has an atomic symbol U, atomic number 92, and atomic weight 238.03. U-235 is used as the fissionable fuel in nuclear weapons and as fuel in nuclear power reactors.Motor Activity: The physical activity of a human or an animal as a behavioral phenomenon.Madagascar: One of the Indian Ocean Islands off the southeast coast of Africa. Its capital is Antananarivo. It was formerly called the Malagasy Republic. Discovered by the Portuguese in 1500, its history has been tied predominantly to the French, becoming a French protectorate in 1882, a French colony in 1896, and a territory within the French union in 1946. The Malagasy Republic was established in the French Community in 1958 but it achieved independence in 1960. Its name was changed to Madagascar in 1975. (From Webster's New Geographical Dictionary, 1988, p714)Dugong: A genus of the order Sirenia characterized by a notched tail, the presence of nasal bones and a long nasal cavity, and large columnar teeth lacking enamel. Dugongs inhabit the coastal waters of the Indian Ocean, Red Sea, and the Malay Archipelago. (From Scott, Concise Encyclopedia Biology, 1996)Central Nervous System Stimulants: A loosely defined group of drugs that tend to increase behavioral alertness, agitation, or excitation. They work by a variety of mechanisms, but usually not by direct excitation of neurons. The many drugs that have such actions as side effects to their main therapeutic use are not included here.Piperidines: A family of hexahydropyridines.Models, Genetic: Theoretical representations that simulate the behavior or activity of genetic processes or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.WyomingReceptor, Metabotropic Glutamate 5: A type I G protein-coupled receptor mostly expressed post-synaptic pyramidal cells of the cortex and CENTRAL NERVOUS SYSTEM.Animal Distribution: A process by which animals in various forms and stages of development are physically distributed through time and space.Reaction Time: The time from the onset of a stimulus until a response is observed.Selection, Genetic: Differential and non-random reproduction of different genotypes, operating to alter the gene frequencies within a population.Marsupialia: An infraclass of MAMMALS, also called Metatheria, where the young are born at an early stage of development and continue to develop in a pouch (marsupium). In contrast to Eutheria (placentals), marsupials have an incomplete PLACENTA.Classification: The systematic arrangement of entities in any field into categories classes based on common characteristics such as properties, morphology, subject matter, etc.Earth (Planet): Planet that is the third in order from the sun. It is one of the four inner or terrestrial planets of the SOLAR SYSTEM.Reproduction: The total process by which organisms produce offspring. (Stedman, 25th ed)Fishes: A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.Life: The state that distinguishes organisms from inorganic matter, manifested by growth, metabolism, reproduction, and adaptation. It includes the course of existence, the sum of experiences, the mode of existing, or the fact of being. Over the centuries inquiries into the nature of life have crossed the boundaries from philosophy to biology, forensic medicine, anthropology, etc., in creative as well as scientific literature. (Random House Unabridged Dictionary, 2d ed; Dr. James H. Cassedy, NLM History of Medicine Division)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.Caribbean Region: The area that lies between continental North and South America and comprises the Caribbean Sea, the West Indies, and the adjacent mainland regions of southern Mexico, Central America, Colombia, and Venezuela.Demography: Statistical interpretation and description of a population with reference to distribution, composition, or structure.Baclofen: A GAMMA-AMINOBUTYRIC ACID derivative that is a specific agonist of GABA-B RECEPTORS. It is used in the treatment of MUSCLE SPASTICITY, especially that due to SPINAL CORD INJURIES. Its therapeutic effects result from actions at spinal and supraspinal sites, generally the reduction of excitatory transmission.