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单词 conditioned reflex
释义

conditioned reflex


Thesaurus
Noun1.conditioned reflex - an acquired response that is under the control of (conditional on the occurrence of) a stimulusconditioned reflex - an acquired response that is under the control of (conditional on the occurrence of) a stimulusacquired reflex, conditional reaction, conditional reflex, conditional response, conditioned reaction, conditioned responselearned reaction, learned response - a reaction that has been acquired by learningconditioned avoidance, conditioned avoidance response - a conditioned response that anticipates the occurrence of an aversive stimulus

conditioned reflex


Conditioned reflex

A learned response performed by a trained animal to a signal that was previously associated with an event of consequence for that animal. Conditioned reflex (CR) was first used by the Russian physiologist I. P. Pavlov to denote the criterion measure of a behavioral element of learning, that is, a new association between the signal and the consequential event, referred to as the conditioned stimulus (CS) and unconditioned stimulus (US), respectively. In Pavlov's classic experiment, the conditioned stimulus was a bell and the unconditioned stimulus was sour fluid delivered into the mouth of a dog restrained by harness; the conditioned stimulus was followed by the unconditioned stimulus regardless of the dog's response. After training, the conditioned reflex is manifested when the dog salivates to the sound of the bell.

Ideally, certain conditions must be met to demonstrate the establishment of a conditioned reflex according to Pavlov's classical conditioning method. Before conditioning, the bell conditioned stimulus should attract the dog's attention or elicit the orienting reflex (OR), but it should not elicit salivation, the response to be conditioned. That response should be specifically and reflexively elicited by the sour unconditioned stimulus, thus establishing its unlearned or unconditioned status. After conditioned pairings of the conditioned stimulus and the unconditioned stimulus, salivation is manifested prior to the delivery of the sour unconditioned stimulus. Salivation in response to the auditory conditional stimulus is now a “psychic secretion” or the conditioned reflex.

To this day, Pavlov's methods provide important guidelines for basic research upon brain mechanisms in learning and memory. Scientists all over the world have paired a vast array of stimuli with an enormous repertoire of reflexes to test conditioned reflexes in representative species of almost all phyla, classes, and orders of animals. As a result, classical conditioning is now considered a general biological or psychobiological phenomenon which promotes adaptive functioning in a wide variety of physiological systems in various phylogenetic settings. See Cognition, Memory

conditioned reflex

an automatic response which has been trained or learnt. A reflex response is a naturally occurring response to a stimulus, for example, salivation is the natural response to the stimulus of food, while the knee jerk is the natural response to a tap below the knee. However, Pavlov (1911) demonstrated that if a neutral stimulus is associated with the natural stimulus, this neutral stimulus becomes conditioned and will alone evoke the response. This response is then called a ‘conditioned reflex’ (see CONDITIONING). The paradigm is useful in explaining faulty learning, especially of fear responses, i.e. the development of phobias.

Reflexes are automatic, often involving emotional responses, not only of fear, but also of anger, pleasure or other emotions. Many human emotional responses can be seen to have developed as a result of conditioning through previous experiences. The term conditioned response is now used in preference.

Conditioned Reflex

 

an acquired, complex adaptive reaction of an animal or man; it is caused by a specific condition (hence its name) and is based on a temporary association between a conditioned stimulus (signal) and an unconditioned reflex act that reinforces the stimulus. Conditioned reflexes are caused by the activity of the highest areas of the central nervous system—the cerebral cortex and the subcortex; they occur during the process of ontogeny and are based on unconditioned reflexes.

The term “conditioned reflex” was introduced in 1903 by I. P. Pavlov. Pavlov’s research led him to devise the conditioned-reflex theory of animal and human behavior, as well as a new theory of brain functions that focused on the physiology of higher nervous activity. The study of the formation and characteristics of conditioned reflexes has furthered knowledge of the brain’s functioning.

Among the many techniques used for studying conditioned reflexes the best known is the method of the salivation reflex, which facilitates a simple and accurate evaluation of conditioned reflexes according to the extent of their development. Although modern electrophysiological, neurochemical, and psychopharmacological methods of analyzing the brain’s activity have provided much new information on conditioned reflexes, Pavlov’s original theories, based on the study of the salivation reflex, remain the foundation for research in the field.

A conditioned stimulus may be any change in the external or internal environment that is received by the body’s receptors. During a conditioned reflex’s initial, or generalization, stage an identical reaction can occur in response to many signals. Later, the conditioned reflex becomes stronger, more specialized, more selective, and more regular in magnitude. Only one signal out of many, or those stimuli that are similar to the signal, are then able to evoke an adequate reaction. If the conditions governing the formation of a conditioned reflex are disrupted, the reflex changes its parameters or disappears.

Variability, which is the most characteristic feature of a conditioned reflex, ensures the body’s adjustment to the external environment. A conditioned signal that gives incorrect information on the external environment ceases to be a stimulus for responsive behavior, and the reaction to such a signal disappears. This phenomenon is based on internal inhibition, which causes a sensitive discrimination among stimuli according to their physiological and biological properties and which helps the body dispense with conditioned reflexes that are no longer biologically useful.

Internal inhibition, which occurs during even the most highly conditioned responses, is the basis of the classification of all conditioned reflexes as either positive or negative. During positive (reinforced) conditioned reflexes, the conditioned signal causes stimulation and specific physiological activity, for example, feeding. In negative (unreinforced) conditioned reflexes, such activity is suppressed owing to the development of internal inhibition.

Depending on the stimulus causing the reflex, conditioned reflexes are classified as either natural or artificial. Natural conditioned reflexes are evoked by the inherent properties of an unconditional reinforcement that have biological significance for an animal, for example, the sight and smell of food. Artificial conditioned reflexes are evoked by stimuli that are initially unconnected to a reinforcement, for example, a bell, a light, or the sound of a metronome.

Conditioned reflexes, in conformity with the biological significance of the unconditional reinforcement, may be food-related (connected with the procurement, intake, and assimilation of food) or protective (defensive). Conditioned reflexes are also classified as autonomic or motor reflexes, according to the nature of the response.

Conditioned reflexes are further differentiated according to the structure of the conditioned stimuli, the relationships between the time required for the action of the conditional and unconditional components, the nature of the reinforcement, and the time that elapses between the signal and the response. These four factors determine the classification of conditioned reflexes into first-order reflexes, based on unconditional reflexes; second- and third-order reflexes, which originate in previously developed temporary relationships; imitative reflexes, in which the behavioral reactions of another animal serve as the reinforcement; associative reflexes, which occur when a conditioned reflex is evoked by two simultaneous indifferent stimuli; and instrumental reflexes, which help an animal procure food or which free it from such unpleasant sensations as pain. During a given type of conditioned reflex the response to the signal does not reproduce the reaction from which the response was developed.

A relatively high level of organization of the central nervous system is a prerequisite for the development of a conditioned reflex; individually acquired forms of behavior in invertebrates are not regarded as conditioned reflexes. True conditioned reflexes occur only in vertebrates: fishes, amphibians, reptiles, birds, and mammals. Higher-order conditioned reflexes are of a complexity that corresponds to the organism’s level of neural organization. In dogs, fifth- and sixth-order conditioned reflexes may be produced, and in monkeys, tenth- through 12th-order reflexes. Man, with his ability to think abstractly, can develop conditioned reflexes of the 20th order or higher. Examples of such complex reactions are the operation of various apparatus and machines, the performance of other types of manual labor, and the motor activities associated with speech.

The analysis and synthesis of stimuli from the external and internal environments are continually perfected during conditioned-reflex activity. The analysis of stimuli consists of the discrimination and separation of signals and of the differentiation in their effects on the body. The synthesis of stimuli is manifested in the association, generalization, and combination of stimuli that originate in different parts of the cerebral cortex owing to the interaction between individual neurons and groups of neurons. The analysis and synthesis of stimuli are interconnected and proceed in a parallel manner; they constitute the main function of the brain. An example of the analytic and synthetic activity of the cerebral cortex is the formation of the dynamic stereotype, which combines several temporary interactions into a functional system. The cortex fixes the order of the stimuli and of their corresponding reactions; this facilitates the cortex’s efficient functioning during the performance of a stereotyped succession of reflexes.

Conditioned reflexes are produced as a result of the closure of the neural link between two simultaneously stimulated parts of the brain. Pavlov’s conclusions about the cortical-closure mechanism of conditioned reflexes have been confirmed by detailed analysis of the neural mechanism of the conditioned-reflex link. This analysis has been based on accurate modern techniques of electroencephalography and the study of evoked potentials and of neuron activity.

According to P. K. Anokhin, the action of conditioned and unconditioned stimuli is accompanied by a generalized activation of the cortex with a subsequent convergence of increasing stimuli in certain neurons. As a result of the interaction on the cellular level between current and former processes of stimulation, temporary associations develop and are established. Every conditioned reflex is based on a system of neuron groups that is capable of reproducing traces of former stimuli in response to a signal. It was originally believed that the excitation from one group of cortical cells which receive this signal is transmitted to another group only along the horizontal nerve fibers that pass through the cortex. However, further research by the Soviet physiologists E. A. Asratian, I. S. Beritashvili, A. B. Kogan, M. M. Khananashvili, and N. Iu. Belenkov has indicated that a new functional connection may occur in a different way: from the cortex to the subcortex and back to the cortex. In addition to the cortex, many subcortical structures, including the reticular formation, the hippocampus, the basal ganglia, and the hypothalamus, contribute to the development of conditioned reflexes.

The development and establishment of a conditioned reflex are accompanied by the formation of a reflex arc, consisting of afferent, central, and efferent areas. Information on the results of a completed action enters the brain by means of feedback.

To a great extent, the multiplicity of conditioned reflexes in animals determines their complex behavior. Conditioned reflexes facilitate an organism’s adaptation to the environment. By means of many indirect signs that acquire the significance of signals, an animal obtains advance knowledge about food or impending danger and adjusts its behavior accordingly. The development of a higher-order conditioned reflex is the synthesis of two temporary connections; during this synthesis there is inhibition in the central and efferent areas of the reflex arc of the original conditioned reflex. The afferent area of the arc, however, becomes involved in the newly developed reflex. Higher levels of integration occur in an analogous way. Asratian’s hypothesis that the development of complex behavioral acts from conditioned reflexes is an integrative process proceeds from a belief that individually acquired behavioral acts are the products of reflex action.

The principles of both elementary and complex conditioned reflexes are the same for animals and man. This leads to a conclusion that is important in terms of natural science and philosophy: that the human brain obeys general biological laws and may be studied objectively. At the same time, the human brain’s activity is qualitatively unique, and its conditioned-reflex activity differs fundamentally from that of animals. This difference is caused by the presence of two signal systems in man.

REFERENCES

Kogan, A. B. Elektrofiziologicheskoe issledovanie tsentral’nykh mekhanizmov nekotorykh slozhnykh refleksov. Moscow, 1949.
Pavlov, I. P. Poln. sobr. tr., vol. 3. Moscow-Leningrad, 1949.
Belenkov, N. Iu. Uslovnyi refleks i podkorkovye obrazovaniia mozga. Moscow, 1965.
Anokhin, P. K. Biologiia i neirofiziologiia uslovnogo refleksa. Moscow, 1968.
Beritov, I. S. Struktura i funktsii kory bol’shogo mozga. Moscow, 1969.
Asratian. E. A. Ocherki po fiziologii uslovnykh refleksov. Moscow, 1970.
Konorski. J. Integrativnaia deiatel’nost’ mozga. Moscow, 1970. (Translated from English.)
Fiziologiia vysshei nervnoi deiatel’nosti, parts 1–2. Leningrad, 1970–71.
Livanov, M. N. Prostranstvennaia organizatsiia protsessov golovnogo mozga. Moscow, 1972.
Eleklricheskaia aktivnost’ golovnogo mozga pri obrazovanii prostykh form vremennoi sviazi. Moscow, 1972.
Milner, P. Fiziologicheskaia psikhologiia. Moscow, 1973. (Translated from English.)
Dmitriev, A. S. Fiziologiia vysshei nervnoi deiatel’nosti. Moscow, 1974.
Rudenko. L. P. Funktsional’naia organizatsiia elementarnykh i slozhnykh form uslovnoreflektornoi deiatel’nosti. Moscow, 1974.
Pribram, K. lazyki mozga. Moscow, 1975. (Translated from English.)

N. F. SUVOROV

conditioned reflex

[kən′dish·ənd ′rē‚fleks] (psychology) Response of an organism to a stimulus which was inadequate to elicit the response until paired for one or more times with an adequate stimulus.

conditioned reflex


reflex

 [re´fleks] a reflected action or movement; the sum total of any particular automatic response mediated by the nervous system. A reflex is built into the nervous system and does not need the intervention of conscious thought to take effect.

The knee jerk is an example of the simplest type of reflex. When the knee is tapped, the nerve that receives this stimulus sends an impulse to the spinal cord, where it is relayed to a motor nerve. This causes the quadriceps muscle at the front of the thigh to contract and jerk the leg up. This reflex, or simple reflex arc, involves only two nerves and one synapse. The leg begins to jerk up while the brain is just becoming aware of the tap.
Other simple reflexes, the stretch reflexes, help the body maintain its balance. Every time a muscle is stretched, it reacts with a reflex impulse to contract. As a person reaches or leans, the skeletal muscles tense and tighten, tending to hold him and keep him from falling. Even in standing still, the stretch reflexes in the skeletal muscles make many tiny adjustments to keep the body erect.
The “hot stove” reflex is more complex, calling into play many different muscles. Before the hand is pulled away, an impulse must go from the sensory nerve endings in the skin to a center in the spinal cord, from there to a motor center, and then out along the motor nerves to shoulder, arm, and hand muscles. Trunk and leg muscles respond to support the body in its sudden change of position, and the head and eyes turn to look at the cause of the injury. All this happens while the person is becoming aware of the burning sensation. A reflex that protects the body from injury, as this one does, is called a nociceptive reflex. Sneezing, coughing, and gagging are similar reflexes in response to foreign bodies in the nose and throat, and the wink reflex helps protect the eyes from injury.
A conditioned reflex is one acquired as the result of experience. When an action is done repeatedly the nervous system becomes familiar with the situation and learns to react automatically, and a new reflex is built into the system. Walking, running, and typewriting are examples of activities that require large numbers of complex muscle coordinations that have become automatic.Nerve pathway of a simple reflex. When the sensory nerve ending is stimulated, a nerve impulse travels along a sensory (afferent) neuron to the spinal cord. Here an association neuron transfers the impulse to a motor (efferent) neuron. The motor neuron carries the impulse to a muscle, which contracts and moves a body part.
abdominal r's contractions of the abdominal muscles about the navel on stimulating the abdominal skin. It indicates that the spinal cord from the eighth to the twelfth thoracic nerve is intact.accelerator reflex an increase in heart rate in response to changes in intrathoracic pressure or respiratory rate; see also reflex" >Bainbridge reflex and reflex" >cardiac respiratory reflex.accommodation reflex the coordinated changes that occur when the eye adapts itself for near vision; they are constriction of the pupil, convergence of the eyes, and increased convexity of the lens.Achilles reflex ankle jerk.acoustic reflex contraction of the stapedius muscle in response to intense sound.anal reflex contraction of the anal sphincter on irritation of the anal skin.ankle reflex Achilles reflex.auditory reflex any reflex caused by stimulation of the vestibulocochlear nerve; especially momentary closure of both eyes produced by a sudden sound.Babinski reflex see babinski reflex.Babkin reflex see babkin reflex.Bainbridge reflex a rise in pressure in, or increased distension of, the large somatic veins or the right atrium causes acceleration of the heart beat. Called also Bainbridge effect.baroreceptor reflex the reflex responses to stimulation of baroreceptors of the carotid sinus and aortic arch, regulating blood pressure by controlling heart rate, strength of heart contractions, and diameter of blood vessels.biceps reflex contraction of the biceps muscle when its tendon is tapped.bite reflex strong closure of the jaws when the teeth or gums are stimulated.Brain's reflex extension of a hemiplegic flexed upper limb when a person is in a quadrupedal posture; called also quadrupedal extensor reflex.bulbocavernosus reflex (bulbospongiosus reflex) contraction of the bulbocavernous muscle in response to a tap on the dorsum of the penis; called also penile reflex.cardiac respiratory reflex an increase in heart rate caused by an increase in respiratory rate that reduces venous return.carotid sinus reflex slowing of the heartbeat when pressure is applied to the carotid artery at the level of the cricoid cartilage. See also carotid sinus syndrome.Chaddock's reflex in lesions of the pyramidal tract, stimulation below the external malleolus causes extension of the great toe; called also Chaddock's sign.chain reflex a series of reflexes, each serving as a stimulus to the next, making a complete activity.ciliary reflex the movement of the pupil in accommodation.ciliospinal reflex dilation of the ipsilateral pupil on painful stimulation of the skin at the side of the neck.clasp-knife reflex clasp-knife rigidity.conditioned reflex conditioned response" >conditioned response.conjunctival reflex closure of the eyelid when the conjunctiva is touched.corneal reflex see corneal reflex.cough reflex the sequence of events initiated by the sensitivity of the lining of the airways and mediated by the medulla as a consequence of impulses transmitted by the vagus nerve, resulting in coughing, i.e., the clearing of the passageways of foreign matter.cremasteric reflex contraction of the ipsilateral cremaster muscle, drawing the testis upward, when the upper inner aspect of the thigh is stroked longitudinally.deep reflex one elicited by a sharp tap on the appropriate tendon or muscle to induce brief stretch of the muscle.digital reflex Hoffmann's sign (def. 2).doll's eye reflex doll's eye phenomenon.embrace reflex Moro reflex.gag reflex elevation of the soft palate and retching which is elicited by touching the back of the tongue or the wall of the pharynx; called also pharyngeal reflex.Areas that react in a gag reflex when touched.gastrocolic reflex increase in intestinal peristalsis after food enters the empty stomach.gastroileal reflex increase in ileal motility and opening of the ileocecal valve when food enters the empty stomach.grasp reflex flexion or clenching of the fingers or toes on stimulation of the palm of the hand or sole of the foot.Hering-Breuer r's see hering-breuer reflexes.Hoffmann's reflex Hoffmann's sign (def. 2).jaw reflex (jaw-jerk reflex) closure of the mouth caused by a downward blow on the passively hanging chin; rarely seen in health but very noticeable in corticospinal tract lesions.knee reflex knee jerk.light reflex 1. constriction of the pupil when a light is shone into the same (direct light reflex) or the opposite eye (indirect or consensual light reflex).2. a luminous image reflected when light strikes the normal tympanic membrane.lung r's Hering-Breuer reflexes.Magnus and de Kleijn neck r's extension of both limbs on the same side, or one limb or part of a limb, with increase of tonus on the side to which the chin is turned when the head is rotated, and flexion with loss of tonus on the side to which the occiput points; it usually indicates decerebrate rigidity" >decerebrate rigidity.Mayer's reflex opposition and adduction of the thumb combined with flexion at the metacarpophalangeal joint and extension at the interphalangeal joint, on downward pressure of the index finger.Mendel-Bekhterev reflex dorsal flexion of the second to fifth toes on percussion of the dorsum of the foot; in certain organic nervous disorders, plantar flexion occurs.micturition reflex any of the reflexes necessary for effortless urination and subconscious maintenance of continence.Moro reflex see moro reflex.myotatic reflex stretch reflex.neck righting reflex rotation of the trunk in the direction in which the head of the supine infant is turned; this reflex is absent or decreased in infants with spasticity.nociceptive r's reflexes initiated by painful stimuli; see also nociceptor and pain.oculocephalic reflex doll's eye phenomenon.orbicularis pupillary reflex unilateral contraction of the pupil, followed by dilatation after closure or attempted closure of eyelids that are forcibly held apart.palatal reflex (palatine reflex) stimulation of the palate causes swallowing. Called also swallowing reflex.paradoxical pupillary reflex reversed pupillary reflex.patellar reflex knee jerk.penile reflex bulbocavernosus reflex.pharyngeal reflex gag reflex.pilomotor reflex the production of flesh" >goose flesh on stroking of the skin.placing reflex flexion followed by extension of the leg when the infant is held erect and the dorsum of the foot is drawn along the under edge of a table top; it is obtainable in the normal infant up to the age of six weeks.plantar reflex plantar flexion of the foot when the ankle is grasped firmly and the lateral border of the sole is stroked or scratched from the heel toward the toes.proprioceptive reflex a reflex that is initiated by stimuli arising from some function of the reflex mechanism itself.psychogalvanic reflex decreased electrical resistance of the body due to emotional or mental agitation.pupillary reflex 1. contraction of the pupil on exposure of the retina to light.2. any reflex involving the iris, resulting in change in the size of the pupil, occurring in response to various stimuli, e.g., change in illumination or point of fixation, sudden loud noise, or emotional stimulation.quadriceps reflex knee jerk.quadrupedal extensor reflex Brain's reflex.red reflex a luminous red appearance seen upon the retina in retinoscopy.reversed pupillary reflex any abnormal pupillary reflex opposite of that which occurs normally; e.g., stimulation of the retina by light dilates the pupil. Called also paradoxical pupillary reflex.righting reflex the ability to assume an optimal position when there has been a departure from it.rooting reflex a reflex in the newborn in which stimulation of the side of the cheek or upper or lower lip causes the infant to turn the mouth and face to the stimulus.Rossolimo's reflex in pyramidal tract lesions, plantar flexion of the toes on tapping their plantar surface.spinal reflex any reflex action mediated through a center of the spinal cord.startle reflex Moro reflex.stepping reflex movements of progression elicited when the infant is held upright and inclined forward with the soles of the feet touching a flat surface; it is obtainable in the normal infant up to the age of six weeks.stretch reflex reflex contraction of a muscle in response to passive longitudinal stretching.sucking reflex sucking movements of the lips of an infant elicited by touching the lips or the skin near the mouth.suck-swallow reflex rhythmical sucking and swallowing movements in an infant when a finger or nipple is placed in the mouth.superficial reflex any withdrawal reflex elicited by noxious or tactile stimulation of the skin, cornea, or mucous membrane, including the corneal, pharyngeal, and cremasteric reflexes.swallowing reflex palatal reflex.tendon reflex contraction of a muscle caused by percussion of its tendon.tonic neck reflex extension of the upper limb and sometimes the lower limb on the side to which the head is forcibly turned, with flexion of the contralateral limbs; seen normally in the newborn. If it persists into the second or third year of life, it indicates a neurologic disorder.triceps reflex contraction of the belly of the triceps muscle and slight extension of the upper limb when the tendon of the muscle is tapped directly, with the limb flexed and fully supported and relaxed.triceps surae reflex Achilles reflex.vestibular r's the reflexes for maintaining the position of the eyes and body in relation to changes in orientation of the head.vestibulo-ocular reflex nystagmus or deviation of the eyes in response to stimulation of the vestibular system by angular acceleration or deceleration or when the caloric test is performed.vomiting reflex the reflex for vomiting" >vomiting, caused by reflexive stimulation of muscles of the gastrointestinal tract and throat; it is mediated by centers in the medulla oblongata and can be set in motion by a variety of stimuli. See also gag reflex.

con·di·tioned re·flex (CR),

a reflex that is gradually developed by training and association through the frequent repetition of a definite stimulus. See: conditioning. Synonym(s): acquired reflex, behavior reflex, conditioned response, trained reflex

con·di·tioned re·flex

(Cr) (kŏn-dish'ŭnd rē'fleks) A reflex that is gradually developed by training and association through the frequent repetition of a definite stimulus.
See: conditioning

conditioned reflex

An automatic response to a stimulus which differs from that initially causing the response but which has become associated with it by repetition. The sight of food causes a dog to salivate. If a bell is rung every time the food appears, the bell alone will, in time, cause salivation.

conditioned reflex


Related to conditioned reflex: conditioned response
  • noun

Synonyms for conditioned reflex

noun an acquired response that is under the control of (conditional on the occurrence of) a stimulus

Synonyms

  • acquired reflex
  • conditional reaction
  • conditional reflex
  • conditional response
  • conditioned reaction
  • conditioned response

Related Words

  • learned reaction
  • learned response
  • conditioned avoidance
  • conditioned avoidance response
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