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Results for “Contrastive learning”

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PubMed1986

Effect of small cue-response separation on pattern discrimination in macaques (Macaca fuscata and M. mulatta).

In order to elucidate the nature of the effect of small cue-response separations on pattern discriminations by monkeys, three studies were performed. When training on a pattern discrimination with a cue-response separation was discontinued during performance at the chance level, there was no saving on the rate of learning a second task (with identical cues but a different cue-response separation) relative to the performance of naive control animals. By contrast, when training was discontinued at a performance level a little better than chance, there was significant saving on learning a second task. After learning the second task, a third task with new pattern cues was learned, with marked saving on the duration of performance at the chance level. The results indicate that during the initial stage of performance at the chance level, monkeys do not attend to cues if there is even a small separation between the cue and the response site.

Animals↗

PubMed2006

Functional imaging of sequence learning in Parkinson's disease.

Sequence learning, a cognitive task linked to cortico-striatal function, is impaired in Parkinson's disease (PD). We chose this task as a behavioral paradigm to study the functional architecture of PD in treated and untreated conditions. In our studies, participants were scanned with H(2)(15)O while performing a kinematically controlled motor sequence learning task and a matching motor baseline task. Experiments revealed that a specific sequence learning network predicts learning in normal subjects, and in independent cohorts of early and advanced PD patients. The analysis of the relationship of network activity to learning performance revealed diverging influences of dopaminergic therapy and deep brain stimulation (DBS). DBS of the internal GP and of STN increased network activity and task performance, while levodopa decreased both measures. In separate studies, we investigated the role of dopaminergic modulation on brain activation during sequence learning. In healthy subjects dopamine transporter (DAT) binding correlated with learning-related brain activation in prefrontal, premotor and cingulate cortices, and in the thalamus. By contrast, in PD most of these regional relationships were lost. Only ventral and dorsolateral prefrontal cortex activation correlated with caudate dopaminergic input. In a final set of studies, we found a significant decline in learning performance in early stage PD patients followed over the course of 2 years. Longitudinal declines in learning-related activation were found in parietal areas, while concomitant increases were localized to the left hippocampus. These observations support hypotheses on disease-stage and task-specific effects within the different cortico-striato-pallido-thalamocortical loops and the mesocortical system in PD.

Aged↗

PubMed1998

A retrospective study of the learning history origins of anxiety sensitivity.

Anxiety sensitivity (AS; the fear of anxiety-related sensations) has been proposed as a risk factor for the development of panic disorder. The present study involved a conceptual replication of Ehlers' (1993, Behaviour Research and Therapy, 31, 269-278) study on childhood learning experiences and panic attacks, but also extended her work by investigating the relationship between early learning experiences and the development of AS, in a non-clinical sample. A sample of 551 university students participated in a retrospective assessment of their childhood and adolescent instrumental and vicarious learning experiences with respect to somatic symptoms (i.e. anxiety and cold symptoms, respectively) using an expanded version of Ehler's (1993) Learning History Questionnaire. AS levels were assessed using the Anxiety Sensitivity Index, and panic history was obtained using the Panic Attack Questionnaire, Revised. Contrary to hypotheses, the learning experiences of high AS individuals were not found to be specific to anxiety symptoms, but involved parental reinforcement of sick-role behavior related to somatic symptoms in general. High AS subjects reported both more anxiety and cold symptoms prior to age 18 than individuals with lower levels of AS. In addition, both cold and anxiety symptoms elicited more special attention and/or instructions from parents for high AS individuals to take special care of themselves. These findings are contrasted with the results for self-reported panickers who reported more learning experiences (modeling and parental reinforcement) specific to anxiety-related symptoms, than the non-panickers. The results suggest that higher-than-normal levels of AS may arise from learning to catastrophize about the occurrence of bodily symptoms in general, rather than anxiety-related symptoms in particular.

Adult↗

PubMed1999

Declarative and procedural memory functioning in abstinent cocaine abusers.

BACKGROUND: We determined the nature and recovery of procedural and declarative memory functioning in a cocaine-abusing cohort in the 45-day period following use. METHODS: Thirty-seven cocaine abusers and 27 control subjects were administered the following memory and mood measures: California Verbal Learning Test, recall of the Rey-Osterrieth Complex Figure Test, Pursuit Rotor Task, and Profile of Mood States at 4 visits (within 72 hours of admission and at 10, 21, and 45 days following abstinence). RESULTS: Analysis of performance on the Rey-Osterrieth Complex Figure Test revealed that both groups improved in their recall over repeated administrations, though the control group recalled significantly more of the information than cocaine subjects during the 45-day interval. Results for the California Verbal Learning Test indicated improved learning for both subject groups over time, but no group x time interaction. On the Pursuit Rotor Task, cocaine abusers improved their performance at a faster rate than controls at visit 1. At day 45 (visit 4), cocaine abusers again showed improvement on the Pursuit Rotor Task, whereas controls demonstrated a relative plateau in rate of learning. CONCLUSIONS: This study documented a lasting detrimental effect on a sensitive nonverbal declarative memory task in cocaine-dependent subjects following abstinence of 45 days. In contrast, abstinence from cocaine during this 45-day period was associated with sustained improvement on a motor learning test in the cocaine abusers relative to controls.

Adult↗

PubMed2005

Sequence learning: response structure and effector transfer.

Two experiments are reported that investigate the response structure and effector transfer of repeated movement sequences. Participants moved a lever to targets sequentially presented on the computer monitor. In Experiment 1 the learning of 10- and 16-element sequences (identical movement pattern) was contrasted. After 1 day of practice the 10-element sequence was organized into fewer subsequences and, thus, performed more rapidly than the 16-element sequence. The imposed organization appeared to be coded in a relatively abstract way, as evidenced by effector transfer that was as good as that on the retention test. In Experiment 2 the 16-element sequence was studied after more extensive practice. By the end of 4 days of practice the participants produced relatively seamless responses void of obvious transitions between subsequences, but the control of the movement was less effector independent than observed earlier in practice. The results suggest that the process of consolidating the sequence, which led to more fluent response production, also resulted in the utilization of effector specific information.

Computers↗

PubMedDate not supplied

Visual discrimination learning in binocularly deprived cats: 20 years of studies in the Nencki Institute.

Data obtained by the author and his colleagues on various forms of visual discrimination learning in cats binocularly deprived of pattern vision with cloth masks (BD cats) are reviewed. In these studies two comparison groups were used: controls reared also in the laboratory but with open eyes (C cats) and cats reared in normal environment outside the laboratory (N cats). Data from other laboratories on lid-sutured and dark-reared BD cats are also shortly reviewed. The BD cats showed several clear-cut deficits. Those in pattern discrimination and in fine contrast discrimination were presumably mainly due to impairment of the perceptual inhibitory learning, whereas those in coping with the partition in the apparatus and in successive discrimination were due to impairment of associative inhibitory learning. The deficits in object discrimination and in interocular transfer were apparently due to a reduced number of binocular neurons in the deprived visual cortex and superior colliculi. Dramatic deficit in relearning after ablation of the superior colliculi-pretectum complex shows a reduced utilization of the abnormal cortex in discrimination learning. The C cats shared fully with BD cats a dramatic impairment in the visually delayed response. This short-term memory deficit was presumably due to a limited practice in visual learning in cage-reared cats. The C cats showed also some impairment in coping with the partition and in relearning after the colliculus-pretectum ablation. The BD cats were not impaired in pattern vs. no-pattern discrimination and in grating discrimination. Thus, visual deprivation does not impair the formation of excitatory and simple inhibitory connections required in crude discrimination. Moreover, presumably due to their less distractibility by external stimuli, the BD cats could be even superior to N and C cats in very crude discrimination tasks.

Animals↗

PubMedDate not supplied

[The interaction of a state of haloperidol-induced catalepsy and a passive-avoidance conditioned reflex].

Injection of haloperidol (2.5 mg/kg) immediately after elaboration of the passive avoidance conditioned reflex stabilized retrieval of the conditioned reflex on the 2nd, 7th, and 14th days. Catalepsy induced by haloperidol injection was increased after the completion of passive avoidance conditioning. Conditioned reflex retrieval decreased catalepsy which was retrieved without repeated haloperidol injection. In contrast to the control animals, in the animals after conditioning the most pronounced catalepsy was observed immediately after the conditioned reflex retrieval with the following stabilization at the lower level. The auto enhancement of catalepsy retrieval was more expressed on the 14th day (as compared with the 7th day) both in the control and learned animals, but in the latter it did not depend on the testing time (in contrast to the control animals.

Animals↗

PubMed1986

Behavioral effects of large and small lesions of the rat medial frontal cortex.

Rats with either sham operations, small medial frontal cortex lesions (SMF), or large medial frontal cortex lesions (LMF) were tested in the open field, for spatial alternation and for 8-arm maze learning. The behaviors of sham-operated and SMF rats were similar on the spatial learning tasks, while the LMF group performed poorly in relation to these two groups. In contrast, the two lesion groups differed from the sham group, but not from each other, on locomotor activity in the open field. The differences in performance between the SMF and LMF groups on the spatial learning measures suggest that medial frontal cortex lesion size and locus may be important factors underlying the variable results of previous studies evaluating spatially-oriented behaviors of rats with varying degrees of medial frontal cortex damage.

Animals↗

PubMed1993

Strain-dependent escape deficit in two rat models of learned helplessness.

The shuttle box escape deficit produced by prior inescapable shock (IS) or by escapable shock (ES) was investigated in Koltushi high- (KHA) and low-avoidance (KLA) rat strains, genetically selected on the basis of divergent acquisition of a conditioned avoidance response in a two-way shuttle box. IS enhanced escape failures only in KHA rats. In contrast, ES produce escape deficit only in KLA rats. These data suggest that the learned helplessness interpretation of escape deficit might be relevant only when IS is administered to KHA rats. In the case of KLA rats exposed to ES, escape deficit represents a coping behavior.

Animals↗

PubMed1988

Absolute and relative measures of dimensional contrast.

Two sets of experiments examined the discriminative performance of pigeons on a visual flicker-rate continuum using a maintained generalization procedure. In the first experiment, responses during the intermediate stimulus value were not reinforced, whereas responses during all other stimuli were reinforced periodically. In the second experiment, training was similar to the first, with the exception of one condition in which stimuli adjacent to the negative stimulus border were eliminated from the discrimination set. Results from both experiments show that positive dimensional contrast seems to represent a relative enhancement of discrimination gradient form, rather than an absolute increase in responding with respect to prior baseline. Further, the form and magnitude of positive dimensional contrast are not predictable from the form and magnitude of baseline response rates. Results from the second experiment indicate that eliminating border stimuli increased response-rate differences between positive and negative stimuli, but did not necessarily diminish the magnitude of positive dimensional contrast.

Animals↗

PubMed2005

A lateralized avian hippocampus: preferential role of the left hippocampal formation in homing pigeon sun compass-based spatial learning.

The hippocampal formation (HF) plays a crucial role in amniote spatial cognition. There are also indications of functional lateralization in the contribution of the left and right HF in processes that enable birds to navigate space. The experiments described in this study were designed to examine left and right HF differences in a task of sun compass-based spatial learning in homing pigeons (Columba livia). Control, left (HFL) and right (HFR) HF lesioned pigeons were trained in an outdoor arena to locate a food reward using their sun compass in the presence or absence of alternative feature cues. Subsequent to training, the pigeons were subjected to test sessions to determine if they learned to represent the goal location with their sun compass and the relative importance of the sun compass vs. feature cues. Under all test conditions, the control pigeons demonstrated preferential use of the sun compass in locating the goal. By contrast, the HFL pigeons demonstrated no ability to locate the goal by the sun compass but an ability to use the feature cues. The behaviour of the HFR pigeons demonstrated that an intact left HF is sufficient to support sun compass-based learning, but in conflict situations and in contrast to controls, they often relied on feature cues. In conclusion, only the left HF is capable of supporting sun compass-based learning. However, preferential use of the sun compass for learning requires an intact right HF. The data support the hypothesis that the left and right HF make different but complementary contributions toward avian spatial cognition.

Animals↗

PubMedDate not supplied

Regularity and/or consistency in the production of the past participle?

In the present study we have investigated the acquisition of the past participle of Italian verbs of the second (including mostly irregular verbs) and third (including mostly regular verbs) conjugations in school age children, and with simulations with an artificial neural network. We aimed to verify the extent to which children are sensitive to regularity, as opposed to the consistency in the mapping from the infinitive to the past participle. In particular, we predicted that children would learn at some point that verbs of the second conjugation tend to be irregular, and therefore they would be more likely to produce irregularizations for verbs of this class, compared to the verbs of the third conjugation. However, they should also show sensitivity to the phonological mapping consistency within each subclass, learning to produce correct forms on the basis of phonological similarity. In contrast, children should be more likely to produce regular forms for verbs of the third conjugation. Thus, a larger regularity effect would be expected for verbs of the third than of the second conjugation, leading to the prediction of a regularity by conjugation interaction.

Child↗

PubMed2002

Dissociable effects of isolation rearing and environmental enrichment on exploration, spatial learning and HPA activity in adult rats.

Male Lister hooded rats were reared from weaning either singly or in groups of three in either barren or enriched cages (n=9 each) to study effects of isolation rearing and environmental enrichment on open-field activity, object exploration, activity in the Light/Dark box (L/D box), spatial learning and memory in the Morris water maze, and hypothalamic-pituitary-adrenal (HPA) activity in response to restraint stress. Regardless of inanimate background, isolation rearing mainly enhanced activity under several conditions of environmental novelty. By contrast, environmental enrichment, regardless of social background, primarily accelerated habituation to novelty and improved spatial learning and memory. None of the treatments significantly altered basal and response levels of plasma ACTH and corticosterone. Furthermore, rats reared singly in barren cages showed persistent activity in the L/D box, indicating an interaction between isolation-induced hyperactivity and reduced habituation due to barren caging. These results show that isolation rearing and environmental enrichment affect behaviour selectively, while at the same time revealing biologically relevant interactions between social and inanimate stimulation. It is concluded that systematic variation of social and inanimate stimulation can help distinguish between effects that generalise across variation in environmental background and effects that are idiosyncratic to a specific environmental background.

Adrenocorticotropic Hormone↗

PubMed1997

Relationships between Pb-induced changes in neurotransmitter system function and behavioral toxicity.

Lead (Pb) exposure impairs learning and results in changes in Fixed Interval (FI) schedule-controlled behavior in experimental animal studies. Studies from our laboratory suggest a major involvement of dopamine systems, and perhaps nucleus accumbens, in the FI performance changes. Dopaminergic (DA), but not other classes of compounds differentially alter FI response rates of control and Pb-treated rats. Marked changes in nucleus accumbens but not striatal D2 and dopamine uptake sites occur in response to Pb. Further, the irreversible DA antagonist EEDQ microinjected into nucleus accumbens but not into striatum suppresses FI performance. In contrast, glutamatergic system disturbances appear to play a key role in the learning impairments caused by Pb. Glutamatergic (GLU) compounds differentially alter learning accuracy levels in control vs. Pb-treated rats, whereas DA compounds do not. Accuracy levels in the learning paradigm were positively correlated with numbers of MK-801 and glutamate binding sites in control rats; these correlations were reversed by Pb exposure. Future studies should be designed to confirm these relationships, to examine the brain regions involved, to determine the extent to which other behaviors known to be mediated by GLU/DA mesocorticolimbic systems are disrupted by Pb, and to address the significance of developmental period of exposure to these effects as well as their reversibility.

Animals↗

PubMed1993

Development of plasticity of brain function with repeated trainings and passage of time after basal forebrain lesions in rats.

Basal forebrain (BF) lesion-induced amnesia in rats is widely used as an animal model of Alzheimer's disease (AD). To study the plasticity of brain function in BF-lesioned rats, we examined the effects of repeated trainings and the passage of time after the lesion on learning ability 3 weeks and 3 months after BF-lesions with ibotenic acid, using an eight-arm radial maze and passive avoidance tasks, and measured choline acetyltransferase (ChAT) activity. Both time and re-training played important roles in the recovery of the ability to learn, as measured with the eight-arm radial maze task, but not the passive avoidance task. In contrast, ChAT activity in the frontal cortex, which was low 3 weeks after the lesion, still low 3 months after lesion, even though the ability to learn had recovered. Recovery of the ability to learn can be attributed to undamaged cholinergic neurons, or to other neuronal systems, or to both. This animal model can be used to demonstrate the plasticity of brain function.

Animals↗

PubMed2006

Contextual cueing in naturalistic scenes: Global and local contexts.

In contextual cueing, the position of a target within a group of distractors is learned over repeated exposure to a display with reference to a few nearby items rather than to the global pattern created by the elements. The authors contrasted the role of global and local contexts for contextual cueing in naturalistic scenes. Experiment 1 showed that learned target positions transfer when local information is altered but not when global information is changed. Experiment 2 showed that scene-target covariation is learned more slowly when local, but not global, information is repeated across trials than when global but not local information is repeated. Thus, in naturalistic scenes, observers are biased to associate target locations with global contexts.

Association Learning↗

PubMed2003

An operational measure of physician lifelong learning: its development, components and preliminary psychometric data.

Despite the emphasis placed on physicians' lifelong learning, no psychometrically sound instrument has been developed to provide an operational measure of the concept and its components among physicians. The authors designed this study to develop a tool for measuring physician lifelong learning, to identify its underlying components and to assess its psychometric properties. A 37-item questionnaire was developed, based on a review of literature and the results of two pilot studies. Psychometric analyses of the responses of 160 physicians identified 19 items that were included in the Jefferson Scale of Physician Lifelong Learning. Factor analysis of the 19 items showed five meaningful factors that were consistent with the definition and major features of lifelong learning. They were 'need recognition', 'research endeavor', 'self-initiation', 'technical skills' and 'personal motivation'. The method of contrasted groups provided evidence in support of the validity of the five factors. The factors' reliability was assessed by coefficient alpha. It is concluded that lifelong learning is a multifaceted concept, and its operational measure is feasible for evaluating different educational programs and for studying group differences among physicians.

Adult↗

PubMed2000

Analogy with knowledgeable learners: when analogy confers benefits and exacts costs.

Though embedding analogy in a text can improve acquisition of concepts that are relatively unfamiliar to learners (Donnelly & McDaniel, 1993), it remains uncertain how analogy influences learning for learners with some background knowledge for the target material. We develop several theoretical possibilities and report an experiment to test these possibilities. Target concepts familiar to college students were expressed either in literal form or through analogy, and the concepts were presented in a manner that either facilitated or discouraged contact with subjects' prior knowledge. As revealed by multiple-choice testing, analogy facilitated learning when the targets were presented to discourage contact with prior knowledge. In contrast, analogy decreased performance when the same targets were presented to facilitate contact with prior knowledge. Possible interpretations of this unique finding are discussed.

Adult↗