Reinforcement conditions and incidental learning in mentally retarded adolescents.
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Adolescent↗
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Results for “CONDITIONED LEARNING”
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The effects of antidepressant drugs on conditioned taste aversion learning of the olfactory bulbectomized rat.
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Amygdala↗
Conditioned c-Fos in mouse NTS during expression of a learned taste aversion depends on contextual cues.
c-Fos expression in the nucleus tractus solitarius (NTS) of the rat has been found to follow administration of a variety of pharmacologically diverse unconditioned stimuli (US), and it has been proposed that NTS is a critical structure in transduction of the US during taste aversion learning. Before conditioning, the conditioned stimulus (CS) taste does not induce c-Fos in NTS, but following pairing of the CS and US, subsequent CS presentation induces c-Fos in NTS. Although it has been suggested that the shift in the c-Fos response following conditioning represents a molecular correlate of taste aversion learning, i.e. the formerly neutral CS now predicts the toxicity associated with the US, the data presented here suggest a more cautious interpretation of c-Fos expression in NTS. In mice, post-conditioning c-Fos expression to the CS depends on contextual cues: when conditioning and testing occur in a novel environment, CS saccharin causes an increase in c-Fos expression, and when conditioning and testing occur in the home cage, CS saccharin produces a decrease in c-Fos expression relative to controls. Furthermore, we show that merely placing an animal into a novel environment is sufficient to drive c-Fos expression in NTS. These data suggest that c-Fos expression in NTS can be driven by a number of different stimuli and conditions, and that these responses may depend on context-dependent activation of forebrain structures shown to drive conditioned c-Fos expression in NTS.
Animals↗
Evidence for an involvement of the mu-type of opioid receptor in the modulation of learning.
Pavlovian conditioning of the rabbit's nictitating membrane response was used to determine whether the retardation of learning produced by enkephalin derivatives was mediated through an action on mu- or delta-opioid receptors. Intraventricular injection of the highly selective mu-agonist, [D-Ala2, MePhe4, Gly-ol5] enkephalin (DAMGO) significantly retarded (2 nmol) or completely blocked (20 nmol) the acquisition of conditioned responses. The retarded or blocked acquisition of conditioned responses produced by DAMGO could still be detected when the rabbits were tested two days after cessation of drug injections, suggesting that DAMGO had affected learning and not simply performance of conditioned responses. Intraventricular injection of a comparable dose (20 nmol) of the highly selective delta-agonist, [D-Pen2,5] enkephalin (DPDPE) did not retard learning. A higher dose of DPDPE (200 nmol), which would be expected to act at both mu- and delta-receptors, did produce a retardation of acquisition that was comparable to the effects of a 2-nmol dose of DAMGO. However, unlike DAMGO, the retardation of learning produced by this dose of DPDPE appeared to be due, at least in part, to a reduction in the aversive properties of the unconditioned stimulus. The retardation of learning produced by 2 nmol of DAMGO and 200 nmol of DPDPE was due to an action on an opioid receptor because this effect was blocked by a subcutaneous injection of naloxone (2.5 mumol/kg), a specific opioid antagonist. The stereoselective effects of the mu-opioid agonist levorphanol further confirmed that the retarded learning was mediated through actions at the mu-opioid receptor. Autoradiographic studies indicated that a 2-nmol, intraventricular dose of DAMGO achieved contents greater than 1 pmol/mg in tissue lying within 2 mm of the lateral ventricle, third ventricle and cerebral aqueduct. These data suggest that enkephalins produce a retardation of learning through an effect on the mu-type of opioid receptor and that at least one locus of their actions is produced at periventricular sites lying within 2 mm of the ventricles.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Patients with cerebellar lesions cannot acquire but are able to retain conditioned eyeblink reflexes.
The purpose of these experiments was to examine the role of the human cerebellum in the acquisition and retention of conditioned reflexes. Normal human subjects and patients with cerebellar lesions were tested for their capacity to acquire, retain and express conditioned eyeblink responses. In acquisition tests, subjects were trained in a delay classical conditioning paradigm using a tone conditioned stimulus and a midline forehead tap as an unconditioned stimulus. While normal subjects developed anticipatory eyeblinks to the tone in one session, patients with cerebellar lesions failed to acquire conditioned responses in four consecutive training sessions. The conditioning deficit was bilateral even in patients with a unilateral cerebellar pathology. The same groups of subjects were tested for the presence of eyeblinks to a visual threat. In these experiments, both normal subjects and patients with cerebellar lesions exhibited a high level of responding when they saw an object approaching their face. These eyeblinks to the visual threat are probably naturally acquired conditioned responses because they extinguish in normal subjects if they are not reinforced by the unconditioned cutaneous stimulus. In addition, the stimulus of seeing an approaching object blocks the acquisition of classically conditioned eyeblinks to a new conditioned stimulus in normal subjects. These data imply that patients with cerebellar lesions who cannot acquire new classically conditioned responses are able to retain and express conditioned eyeblinks which were acquired before the onset of the pathology. Consequently, cerebellum-dependent neural substrates which are involved in learning new conditioned reflexes do not seem to be required for the storage of naturally learned conditioned responses.
Adult↗
Learning: classical and avoidance conditioning the mollusk Pleurobranchaea.
Naive specimens of the marine gastropod Pleurobranchaea withdraw from tactile stimulation of the oral veil and show feeding responses to food chemicals. Experimental subjects, trained by pairing touch (conditioned stimullus) with food chemicals (unconditioned stimulus), soon acquired a classically conditioned feeding response to touch alone. Control subjects that received touch alone or unpaired touch and food chemicals showed significantly fewer feeding responses to touch than did experimentals. Classically conditioned specimens were used for avoidance conditioning. Subjects that received aversive electrical stimulation when they did not withdraw from touch rapidly learned to withdraw rather than to feed in response to touch alone. Controls that received touch alone or unpaired touch and shock continued to exhibit the feeding response to touch alone. The learned responses persisted for up to 2 weeks without reinforcement before extinction, and could be demonstrated in the isolated nervous system.
Animals↗
Invariance of retinal output during visual learning.
Visually conditioned heart-rate change in the pigeon has been developed as a vertebrate model system for the cellular analysis of associative learning. This development included identifying the visual pathways that transmit the conditioned stimulus information. That, in turn, established a foundation for neurophysiological analyses during conditioning to determine whether these pathways behave merely as input lines or undergo training-induced modification. We began this analysis at the visual periphery, the retina. By recording the activity of single optic tract fibers over the acquisition of the conditioned response it was demonstrated that neither the maintained nor CS-evoked activity of retinal ganglion cells are modified during non-associative or associative paradigms. Thus, the data (a) describe the temporal properties of the CS-evoked retinal response, (b) exclude various possibilities that might have modified this response during learning, and (c) establish a firm foundation for cellular neurophysiological analysis of central visual structures involved in transmitting the CS information.
Animals↗
The peripheral unconditioned stimulus pathway in a model learning system involving defensively conditioned heart rate change in the pigeon.
The peripheral pathway transmitting the unconditioned stimulus information is described in a vertebrate model system for studying learning-visually conditioned heart rate change in the pigeon. In this system footshock serves as the unconditioned stimulus, and it is shown that the effective stimulation field of this stimulus, defined with respect to the unconditioned cardioacceleratory response, includes cutaneous dermatomes 21-25 (L1-Sl). The stimulus information is then transmitted by Group III and IV fibers in portions of the femoral and sciatic nerves which enter the spinal cord over segments 21-25. Further, it is shown that interrupting this pathway by section of dorsal roots 21-25 precludes establishing conditioned heart rate change with footshock as the unconditioned stimulus.
Action Potentials↗
Dynorphin A (1-13) and responsiveness of the newborn rat to a surrogate nipple: immediate behavioral consequences and reinforcement effects in conditioning.
The role of endogenous opioid system in learning (Pavlovian conditioning) and reinforcement was studied in newborn rats by pairing central injection of dynorphin A (1-13), an endogenous ligand with high affinity for kappa opioid receptors, with a surrogate nipple. For conditioning, the nipple served as the conditioned stimulus and dynorphin as the unconditioned stimulus. Dynorphin was found to elicit an immediate unconditioned, dose-dependent increase in the neonatal responsiveness to a surrogate nipple providing water, an effect apparently mediated through the kappa opioid receptors. This immediate effect of dynorphin was evident in the context of suckling behavior but not in the context of adult-like drinking when water was delivered through an intra-oral cannula. One hour after injection, the unconditioned stimulatory effect of dynorphin had dissipated and no longer affected responsiveness to the nipple. However, pairing of centrally injected dynorphin and suckling on a nipple delivering water substantially enhanced responsiveness to a nipple 1h later. This suggested conditioning, and hence reinforcement, by the centrally injected dynorphin. The conditioned sustained nipple attachment was mediated through both kappa and micro opioid receptors. These experiments confirm a central role for the brain opioid systems in reinforcement of neonatal behavior on the nipple.
Animals↗
The generality of the incentive-motivational effects of classically conditioned stimuli in instrumental learning.
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Animals↗
The misbehavior of value and the discipline of the will.
Most reinforcement learning models of animal conditioning operate under the convenient, though fictive, assumption that Pavlovian conditioning concerns prediction learning whereas instrumental conditioning concerns action learning. However, it is only through Pavlovian responses that Pavlovian prediction learning is evident, and these responses can act against the instrumental interests of the subjects. This can be seen in both experimental and natural circumstances. In this paper we study the consequences of importing this competition into a reinforcement learning context, and demonstrate the resulting effects in an omission schedule and a maze navigation task. The misbehavior created by Pavlovian values can be quite debilitating; we discuss how it may be disciplined.
Animals↗
The effects of CS-US interval on avoidance conditioning in the rat.
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Animals↗
General conditions for predictivity in learning theory.
Developing theoretical foundations for learning is a key step towards understanding intelligence. 'Learning from examples' is a paradigm in which systems (natural or artificial) learn a functional relationship from a training set of examples. Within this paradigm, a learning algorithm is a map from the space of training sets to the hypothesis space of possible functional solutions. A central question for the theory is to determine conditions under which a learning algorithm will generalize from its finite training set to novel examples. A milestone in learning theory was a characterization of conditions on the hypothesis space that ensure generalization for the natural class of empirical risk minimization (ERM) learning algorithms that are based on minimizing the error on the training set. Here we provide conditions for generalization in terms of a precise stability property of the learning process: when the training set is perturbed by deleting one example, the learned hypothesis does not change much. This stability property stipulates conditions on the learning map rather than on the hypothesis space, subsumes the classical theory for ERM algorithms, and is applicable to more general algorithms. The surprising connection between stability and predictivity has implications for the foundations of learning theory and for the design of novel algorithms, and provides insights into problems as diverse as language learning and inverse problems in physics and engineering.
Algorithms↗
The effect of varying the temporal distribution of conditioning trials on equine learning behavior.
Two experiments were conducted to study the effect of varying the temporal distrbution of conditioning sessions on equine learning behavior. In the first experiment, 15 ponies were trained to clear a small hurdle in response to a buzzer in order to avoid a mild electric shock. Three treatments were used. One group received 10 learning trials daily, seven times a week; one group was trained in the same fashion two times a week and one group was trained once a week. The animals conditioned only once a week achieved a high level of performance in significantly fewer sessions than the ones conditioned seven times a week, although elapsed time from start of training to completion was two to three times greater for the former group. The twice-a-week group learned at an intermediate rate. In the second experiment, the ponies were rearranged into three new groups. They were taught to move backward a specific distance in response to a visual cue in order to avoid an electric shock. Again, one group was trained seven times a week, one group was trained two times and one group was trained once a week. As in the first experiment, the animals trained once a week achieved the learning criteria in significantly fewer sessions than those trained seven times a week, but, as in trial 1, elapsed time from start to finish was greater for them. The two times-a-week group learned at a rate in-between the rates of the other two groups.
Animals↗
Comparison of learning-related neuronal activity in the dorsal premotor cortex and striatum.
Previous studies have reported learning-related changes in neuronal activity during conditional visuomotor learning, also known as arbitrary sensorimotor mapping, conditional visual discrimination, and symbolic or endogenous mapping. Qualitatively similar observations have been reported for the dorsal premotor cortex, the supplementary eye field, the prefrontal cortex, the hippocampus, the striatum and the globus pallidus. The fact that cells in both the dorsal premotor cortex (PMd) and the basal ganglia show changes in activity during associative learning enables a test of the hypothesis that cortex and basal ganglia function in distributed architectures known as cortical-basal ganglionic modules or 'loops'. We reasoned that if these loops represent functional entities, as proposed, then learning-related changes in activity should occur simultaneously in both the cortical and striatal nodes of a loop. The present results confirmed this prediction; as monkeys learned conditional visuomotor associations, neurons in the premotor cortex and associated parts of the putamen changed their rates at approximately the same time. For the largest number of neurons, the evolution in neural activity occurred in close correspondence to the monkeys' learning curves. As a population, however, learning-related changes in activity continued after the monkeys reached an asymptote in performance.
Action Potentials↗
Gustatory thalamus lesions in the rat: II. Aversive and appetitive taste conditioning.
The learning capacities of rats with electrolytic lesions of the gustatory thalamus (GT) were investigated in 3 experiments. In Experiment 1, the presence of a taste cue failed to overshadow odor aversion learning in the lesioned rats, yet these same animals acquired normal taste and odor aversions. Thalamic lesions had no discernible effect on the acquisition of a conditioned flavor preference in Experiment 2. Finally, GT lesions completely reversed the anticipatory contrast effect shown by control subjects in Experiment 3. These results suggest that damage to the GT spares taste detection and recognition and simple associative learning but interferes with learning that involves more complex gustatory information processing.
Animals↗
What is learned in patterning discriminations? Further tests of configural accounts of associative learning in human electrodermal conditioning.
Two Pavlovian SCR conditioning experiments investigated positive and negative patterning discriminations in humans by means of transfer tests. In Experiment 1, positive patterning (A-,B-,AB+) was trained interleaved with non-reinforced presentations of an additional stimulus (C-). Then responding to new compounds consisting of either already trained elements (AC,BC) or new elements (DE) was examined. In Experiment 2, negative patterning (A+,B+,AB-) was trained interleaved with reinforced presentations of an additional stimulus (C+). Again, we examined responding to new compounds consisting of either already trained elements (AC,BC) or new elements (DE). In both experiments the initial patterning discrimination was solved successfully. The response patterns to the test compounds in both experiments were in contradiction to configural accounts of associative learning. In positive patterning human participants seemed to utilize 'number' or some other abstract feature in preference to available concrete stimuli. In negative patterning the abstract dimension of 'separate-versus-together' or 'opposite' was used.
Adult↗
Pedunculopontine tegmental nucleus lesions impair stimulus--reward learning in autoshaping and conditioned reinforcement paradigms.
The role of the pedunculopontine tegmental nucleus (PPTg) in stimulus-reward learning was assessed by testing the effects of PPTg lesions on performance in visual autoshaping and conditioned reinforcement (CRf) paradigms. Rats with PPTg lesions were unable to learn an association between a conditioned stimulus (CS) and a primary reward in either paradigm. In the autoshaping experiment, PPTg-lesioned rats approached the CS+ and CS- with equal frequency, and the latencies to respond to the two stimuli did not differ. PPTg lesions also disrupted discriminated approaches to an appetitive CS in the CRf paradigm and completely abolished the acquisition of responding with CRf. These data are discussed in the context of a possible cognitive function of the PPTg, particularly in terms of lesion-induced disruptions of attentional processes that are mediated by the thalamus.
Animals↗