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Results for “Contrastive learning”

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At least 883 records · Page 49Linked to original sources

PubMed2003

Developmental D-methamphetamine treatment selectively induces spatial navigation impairments in reference memory in the Morris water maze while sparing working memory.

In previous studies, we have shown that P11-20 treatment with D-methamphetamine (MA) (10 mg/kg x 4/day at 2-h intervals) induces impairments in spatial learning and memory in the Morris water maze after the offspring reach adulthood. Using a split-litter, multiple dose, design (0, 5, 10, and 15 mg/kg MA administered s.c. 4/day at 2-h intervals), the spatial learning effect was further explored with a multiple shifted platform (reversal), reference memory-based procedure and a working memory procedure. Prior to spatial learning, animals were first tested for swimming ability (in a straight swimming channel), sequential learning (in the Cincinnati multiple-T water maze), and proximal cue learning (in the Morris water maze). Rats were then assessed in the hidden platform, reference memory-based spatial version of the Morris maze for acquisition and on five subsequent phases in which the platform was moved to new locations. After the reference memory-based, fixed platform position learning phases, animals were tested in the trial-dependent, matching-to-sample, working memory version of the Morris maze. No group differences were found in straight channel, sequential maze, or cued Morris maze performance. By contrast, all MA groups were impaired in spatial learning during acquisition, multiple shift, and shifted with a reduced platform phases of reference memory-based learning. In addition, MA animals were impaired on memory (probe) trials during the acquisition and shifted with a reduced platform phases of learning. No effects on trial-dependent, matching-to-sample, working memory were found. The findings demonstrate that neonatal treatment with MA induces a selective impairment of reference memory-based spatial learning while sparing sequential, cued, and working memory-based learning.

Animals↗

PubMed2004

[Medical education and patient education: new teaching strategies and new communication dynamics].

INTRODUCTION: This study was designed to shed light on the learning difficulties of diabetic patients. MATERIALS AND METHODS: An open-ended questionnaire was sent to 50 patients and 50 diabetics patients and 100 health care professionals working in the field of diabetes and nutrition who had been trained in patient education techniques. They were asked to describe the skills that were the easiest to teach patients and those that patients mastered the best, as well as the skills they found hardest to teach patients, those that patients mastered the least and those that gave rise to errors persisting after the patients education was completed. RESULTS: On the whole, the results showed that the educators found it easy to teach techniques: patients mastered procedures well and made few mistakes. In contrast, diabetic patients seem to have problems learning skills, such as insulin dose adjustment, that require complex problem-solving (involving multiple variables). CONCLUSIONS: Based on these findings, the authors discuss the notions of learning complexity and the time needed for successful patient education.

Communication↗

PubMed1993

On the role of the hippocampus in learning and memory in the rat.

An overview of lesion experiments concerned with the involvement of the hippocampus in learning and memory in the rat is presented. Multiple injections of small amounts of ibotenic acid were used to selectively remove the hippocampus (dentate gyrus, hilar cells, CA1-CA3 pyramidal cells). Similar selective, axon-sparing ibotenate lesions of hippocampus were used in a series of learning and memory experiments employing tasks that are thought to be important in hippocampal function. The performance of rats with the hippocampus removed was compared with that of control animals in the acquisition and retention of spatial versus nonspatial information, forgetting of spatial and nonspatial information, contextual learning, recognition memory and concurrent discrimination learning, and complex representational learning (conditional discrimination and negative patterning learning). The general finding that rats without a hippocampus were impaired on those tasks that required the utilization of spatial and contextual information stands in contrast with the spared performance that was found in learning about and handling (even complex) nonspatial information. Rather than support for views that emphasize a role for the hippocampus in specific memory processes (working memory, declarative memory, temporary memory buffer, configural learning), the present results are more compatible with the idea that the hippocampus plays an especially important role in processing and remembering spatial and contextual information. The limited data that are available using more selective lesions of related hippocampal formation structures (entorhinal cortex, subiculum) suggest that these structures also make important contributions to learning and memory, and that some of these contributions may be different from those made by the hippocampus.

Animals↗

PubMed1993

The role of the amygdala and dorsal raphe nucleus in mediating the behavioral consequences of inescapable shock.

It has been argued that exposure to inescapable shock produces later behavioral changes such as poor shuttle box escape learning because it leads to the conditioning of intense fear, which later transfers to the shuttle box test situation and interferes with escape. Both fear, as assessed by freezing, and escape were measured in Sprague-Dawley rats 24 hr after exposure to inescapable shock. Lesions of the basolateral region and central nucleus of the amygdala eliminated the fear that transfers to the shuttle box after inescapable shock, as well as the fear conditioned in the shuttle box by the shuttle box shocks. However, the amygdala lesions did not reduce the escape learning deficit produced by inescapable shock. In contrast, dorsal raphe nucleus lesions did not reduce the fear that transfers to the shuttle box after inescapable shock, but eliminated the enhanced fear conditioning in the shuttle box as well as the escape deficit. The implications of these results for the role of fear and anxiety in mediating inescapable shock effects are discussed.

Amygdala↗

PubMed2006

Sensitivity to effective relational complexity in the occipitoparietal lobe.

Previous work identified bilateral regions in the occipitoparietal lobe sensitive to the complexity of relational information [Phillips, S., Niki, K., 2003. Increased bilateral occipitoparietal activity for retention of binary versus unary indexed lists in pair recognition. NeuroImage 20 (2), 1226-1235]. Here, we investigate the effect of learning on sensitivity to relational complexity. Eight subjects were scanned on a pair recognition task before, during and after a 2-week training period when subjects learned to recognize a set of shape pairs. For each trial of the pair recognition task, subjects determined whether a probe pair appeared in a list of learned or novel pairs. In the low/high relational complexity condition, every pair in list AB CD EF/AB AD CB was uniquely identifiable by an item in either/both the first or/and second position. Whole-brain and region of interest contrasts revealed a significant interaction between complexity and learning in the occipitoparietal lobe. The increase in activity for the retention of high versus low complexity lists was greater for learned than novel pair lists. Subjects were more likely to respond to low complexity lists as though they were high complexity prior to training. The results suggest that this region provides a window into effective relational complexity, that is, complexity of relational information as processed by the subject, not as presumed by task design.

Adult↗

PubMedDate not supplied

Relationship of age-related decline across several behavioral domains.

These studies were designed to assess whether aged rats have a similar degree of impairment across a number of behavioral tasks. In Experiment 1, no relationship between the severity of a spatial learning impairment and reaction time performance was found among aged rats. This result is in contrast with a relationship that was found in aged rats between spatial learning and the rate of recovery from gustatory neophobia (results of Experiments 2 and 3). Experiment 3 further showed that the relative spatial learning abilities of two subgroups of aged rats, i.e., "impaired" and "unimpaired," were related to transfer training in the water maze conducted six weeks after the completion of original training. The subgroups of aged animals were also distinguished by their latencies (but not errors) on a circular holeboard maze, and the pattern of water consumption during the light/dark cycle determined at the end of the entire protocol (13th week of testing). Other measures, however, did not distinguish the aged subgroups that were formed on the basis of spatial learning ability.

Aging↗

PubMed2005

A new mathematical model for assessment of memorization dynamics.

A new memory model is proposed based on regression analysis and exponential- shaped learning curves. The efficacy of the model is tested with several types of experiments including food aversion in snails, maze learning in rats and memory tests for adults and children. The model is also tested on drug abusers and alcoholics. The results of goodness of fit tests indicate that our model can accurately be used to predict the memory dynamics of diverse experiments and populations. The model can also be used to predict both group and individual performance. The application of the model to detect memory impairment is discussed, as are limitations.

Adult↗

PubMed1976

Effect of pulvinar lesions on visual pattern discrimination in monkeys.

This study compares the performance (percent correct responses and reaction times) of three unoperated control monkeys with the postoperative performance of eight monkeys with pulvinar lesions, either inferior pulvinar or medial and lateral pulvinar, on a tachistoscopically presented visual pattern-discrimination task highly demanding of attention. To further emphasize and assess the attentional factor in visual pattern discrimination, all monkeys who attained criterion performance (90% correct response on three consecutive sessions of 100 trials each) were tested for the effects of visually distracting interference stimuli added to the original discriminative stimuli. In addition, retention of postoperatively learned discriminations was tested after a 6-wk interval withou training and compared with the performance of control monkeys. Four monkeys with only inferior pulvinar lesions and one monkey with inferior pulvinar plus medial and lateral pulvinar lesions were markedly impaired in the postoperative learning of a visual pattern discrimination. Three of these monkeys failed to acquire criterion perfromance in 9,000 or more training trials, while two learned to ceiterion level only after prolonged training (7,400 and 6,900 trials). In contrast, monkeys with medial and lateral pulvinar lesions showed no deficit in learning ability compared to unoperated control monkeys. Furthermore, the performance of the two monkeys with inferior pulvinar lesions, who attained the criterion level of learning only with difficulty, was further impaired by the addition of distracting interference stimuli, where the performance of monkeys with medial and lateral pulvinar lesions as well as the control monkeys was only temporarily disrupted by this procedure. None of the monkeys with pulvinar lesions, who were tested for retention of the postoperatively learned discrimination, showed appreciable deficits in comparison to control monkeys. All monkeys, including controls and those uith pulvinar lesions who were able to learn the visual pattern discrimination, showed a common pattern of reaction time (RT) change during the course of the learning; that is, RT was low during change-level performance, increased during learning, and decreased once criterion performance was achieved. Reaction times of monkeys with inferior pulvinar lesions tended to be longer than for controls or for those with medial and lateral pulvinar lesions. These results provide the first behavior evidence that the inferior pulvinar of monkeys is involved in visual pattern discrimination and add further support to the concept of a second visual system in which the inferior pulvinar plays a role. The attentional aspects of the visual pattern-discrimination task employed in this study and the additional effects obtained with distracting stimuli suggest that the impairments arising from inferior pulvinar lesions may be dependent in part on visual attentional factors.

Acoustic Stimulation↗

PubMed1984

Behavior and academic achievement in hyperactive subgroups and learning-disabled boys. A six-year follow-up.

Hyperactive boys with and without conduct disorder and a contrast group of boys with specific reading disability were compared on behavior ratings and academic achievement six years after their initial examination to clarify the relationship between hyperactivity and learning disability. Both hyperactive groups were rated as problematic on dimensions of overactivity, inattention, and impulsivity. Hyperactive boys who had earlier been undersocialized and aggressive continued to have problems with aggression, while the "pure" hyperactive boys did not. Achievement measures showed performance to be normal for both subgroups, and the incidence of learning disability was only 8%. Reading-disabled youngsters, in contrast, showed only a behavior problem with inattention, yet they all continued to exhibit significant achievement delays. These findings suggest that, while hyperactivity and learning disability may coexist, the incidence of such overlap is less than previously estimated.

Achievement↗

PubMed2005

Early age-related cognitive impairment in mice lacking cannabinoid CB1 receptors.

The molecular mechanisms contributing to the normal age-related decline of cognitive functions or to pathological learning and memory impairment are largely unknown. We demonstrate here that young mice (6-7 weeks) with a genetic deletion of the cannabinoid CB1 receptor performed as well as WT mice, or often better, in a number of learning and memory paradigms, including animal models of skill-learning, partner recognition, and operant conditioning. In contrast, the performance of mature mice (3-5 months) lacking CB1 receptors was much worse than that of age-matched WT animals. In most tests, these mice performed at the same level as old animals (14-17 months), suggesting that the decline in cognitive functions is accelerated in the absence of CB1 receptors. This rapid decline in CB1-deficient animals is accompanied by a loss of neurons in the CA1 and CA3 regions of the hippocampus.

Aging↗

PubMed1999

Neuropsychological deficits associated with antiphospholipid antibodies.

Neurologic events associated with antiphospholipid antibodies (aPAs) include transient ischemic attack, stroke, and vascular dementia in individuals much younger than is typically observed with these disorders. The present study evaluated 27 non-elderly adults with aPAs but without concurrent disease processes or history of neurologic event and 27 age- and education-matched controls. MANOVA (p <.01) indicated group differences in executive functioning, verbal learning and memory, and visuospatial ability. In contrast, gross attentional processes and fine motor skills appeared unaffected by the <?Pub Caret>syndrome. Moreover, the frequency of impaired neuropsychologic performance was greater among individuals with aPAs than among controls (p <.01). The presence of cognitive deficits in otherwise asymptomatic patients with aPAs indicates a preclinical phase of neurologic involvement and may prove to be the most sensitive markers of the syndrome.

Antibodies, Antiphospholipid↗

PubMedDate not supplied

Learning and memory in rats gestationally and lactationally exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

Recently we reported that in utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or coplanar polychlorinated biphenyls (PCBs) resulted in a reduction of errors on a radial arm maze (RAM) working memory task. The effect was more pronounced in males than in females. In this study, we further investigated the effects of in utero and lactational exposure to TCDD on learning and memory by testing male and female TCDD-exposed rats on three different spatial learning and memory tasks: the RAM, the Morris water maze (MWM), and spatial discrimination-reversal learning (RL), as well as on a nonspatial learning task, visual RL. Time-mated Sprague-Dawley rats were gavaged with either TCDD (0.1 microg/kg/day) or corn oil vehicle on gestation days 10-16. Litters were culled to eight on day 2 and weaned on day 21. Beginning on day 80, one male and one female from each litter were tested on the same RAM working memory task used in the previous study. Again, the TCDD-exposed male rats displayed a pronounced decrease in errors relative to control males. Following the RAM testing, the same animals were tested on the MWM, but no differences between the exposed and control rats were observed. Another male and female from each litter were tested on spatial RL on a T-maze. There were no differences between the exposed and control rats on this task. Following spatial RL, the same rats were tested on visual RL on the same maze. The exposed animals did not differ from controls on original learning, but took more trials to reach criterion on the first and second reversals. These results demonstrate a reliable, but task-specific, facilitation of spatial learning and memory in male rats exposed to TCDD during gestation and lactation. In contrast, both male and female TCDD-exposed rats showed a deficit in learning on the visual RL task. This pattern is consistent with that seen in earlier monkey studies. Perinatally TCDD-exposed monkeys were facilitated on certain spatial tasks, but impaired on visual RL tasks.

Analysis of Variance↗

PubMed2001

Ketamine Prevents Learning Impairment When Administered Immediately after Status Epilepticus Onset.

Permanent cognitive impairment is common following status epilepticus (SE) in both humans and animals. We examined the effect of the NMDA antagonist ketamine administered after SE onset on two forms of associative learning in the rat: conditioned taste aversion and fear-conditioned analgesia. Following the onset of lithium/pilocarpine-induced SE, rats were administered either ketamine (100 mg/kg) or acepromazine (25 mg/kg). Acepromazine-treated animals show marked deficits in both learning measures at 1 month after SE. In contrast, ketamine-treated and nonepileptic control animals did not differ in performance for either task. Although studies have shown that ketamine is ineffective at controlling electrographic seizures early in SE, these results are consistent with previous studies showing that ketamine can preserve learning proficiency if administered shortly after seizure onset. As a clinically available drug, ketamine may prove useful in the treatment of SE when combined with conventional antiepileptic strategies.

Journal Article↗

PubMed2000

Neural substrates for the recognition of newly learned faces: a functional MRI study.

Face recognition is critical to the appreciation of our social and physical relations. Functional magnetic resonance imaging (fMRI) was used to identify brain regions involved in the recognition of newly learned faces. Two experiments were conducted. Experiment 1 contrasted a fixation control task with a face recognition task in which subjects were exposed solely to previously viewed faces (all-target). Experiment 2 compared a fixation control with another face recognition task in which subjects were presented with both novel and viewed faces (half-target). Compared to the fixation control, the all-target face recognition was associated with activation in the bilateral occipital and occipitotemporal regions, whereas the half-target face recognition produced activation in the right parietal and prefrontal regions, in addition to the occipital and occipitotemporal. The all-target minus half-target comparison revealed significant activation in the bilateral fusiform gyrus, suggesting stronger fusiform activity during the all-target than the half-target face recognition. The half-target minus all-target comparison showed significant activation in the superior and inferior parietal lobules and several regions in the right frontal lobe. These findings demonstrated that the bilateral fusiform gyrus is involved, not only in face perception, but in a certain aspect of face recognition memory and that this aspect is related to the actual recognition of previously viewed faces rather than the processing of novel ones, which results are consistent with previous lesion work. The right parietal and frontal regions, in contrast, are differentially more associated with the processes related to the detection of novel faces or retrieval effort.

Adult↗

PubMed1996

Machine learning paradigms for pattern recognition and image understanding.

In this paper some issues are considered related to the encoding of spatial information and associated perceptual learning algorithms which, it is claimed, are necessary for robust pattern and object recognition in multi-object (natural) scenes. The types of learning requirements within a 'recognition-by-parts' paradigm are contrasted with findings from alternative models.

Form Perception↗

PubMed1977

Environmental health education: a different orientation.

The indiviual behaviour, group habits and corporate activities that are the keys to environmental prevention are markedly different in character from the personal hygiene and illness behaviours of primary care and patient education. Education for personal care is oriented towards the educatee's own future behaviour and related to the internal processes of his or her physiological organism. It is learning that is aimed both at children and adults. In contrast, in environmental prevention, education is oriented to changing present behaviour related to external stressers and feedbacks. In most programmes this learning is aimed at adults. The health education impact on environmental risks differs in three distinct types of environmental programmes i.e.: (1) when control applies cost-effective technological advances (sewer systems, etc.) which usually bring about behaviour change with little educational effort; (2) when the programme aims at correcting infectious or injurious conditions which require adequate motivation on the part of the people; and (3) when the focus is on social stressers and behaviours, on the reduction of chronic diseases and mental disorders, an area where education and community organization have then a major role to play. Do techniques that effectively develop awareness, communicate information, develop individual or group know-how, and thus lead to preventive action differ between patient behaviour education and environmental health education? The answer must be a partial but important "yes". In environmental prevention programmes the motivating appeal has to be more altruistic, more "other" oriented, and the programme has to be group involving. The behaviours to be changed are not one's own alone, but those common among individuals or corporate bodies around one. In fact, health education faces five challenging problems in the area of environmental risk prevention. First, how do we most quickly and effectively communicate our concern about some stresser or behavioural matter to a specific population? Second, how can we keep voluntary community organizations, which we have helped to develop, from faltering or expiring after three or four years of useful endeavour? Third, how do we reach the populations typified by anomic personalities--the withdrawn, disillusioned or apathetic? Fourth, how do we identify key influential people and interest them in becoming involved in our environmental programmes, in participating in the setting of priorities and contributing to their realization? And last but not least, how can we best ensure that health education services will be provided to community organizations long enough in order to obtain confirmation that the population's behaviour changes have become self-continuing habits or customs?

Ecology↗

PubMed2007

The influence of four serotonin-related genes on decision-making in suicide attempters.

Genetic factors have been associated with the vulnerability to suicidal behavior. We previously reported decision-making impairment in suicide attempters and hypothesized that these cognitive alterations may represent an endophenotype of suicidal behavior. In this study, we aimed to investigate the influence of four serotonin-related genes relevant to suicidal behavior on decision-making, in a large population of suicide attempters. The Iowa Gambling Task was used to assess decision-making in 168 patients with a personal history of attempted suicide. Patients were genotyped for four serotonergic polymorphisms: 5HTTLPR, TPH1 A218C, MAOA u-VNTR, and TPH2 rs1118997. Patients carrying the 5HTTLPR-ll and -sl, TPH1-CC and -AC, MAOA-HH (in women) and TPH2-AA genotypes significantly improved their performance during the task, suggesting a genetic modulation of the learning process required for advantageous decision-making. In contrast, genotypes previously associated with a higher risk of suicidal behavior, a greater sensitivity to the environment and a higher propensity to negative feelings are those conferring poorer learning abilities. We hypothesize that the influence of genetic factors on the vulnerability to suicidal behavior may partly be achieved through their modulation of decision-making and particularly its learning component.

Adolescent↗

PubMed2004

Intrahippocampal administration of the alpha-keto acids accumulating in maple syrup urine disease provokes learning deficits in rats.

Learning disability is a common feature of patients affected by maple syrup urine disease (MSUD). However, the pathomechanisms underlying learning deficit in this disorder are poorly known. In the present study, we investigated the effect of acute administration of the alpha-keto acids accumulating in MSUD into the hippocampus on the behavior of rats in the open field and in the inhibitory avoidance tasks. Adult male Wistar rats received intrahippocampal injections of alpha-ketoisocaproic acid (KIC, 8 micromol), alpha-ketoisovaleric acid (KIV, 5 micromol), alpha-keto-beta-methylvaleric acid (KMV, 5 micromol), or NaCl (8 micromol) (controls) immediately after or 10 min before training. Testing session was performed 24 h later. Posttraining administration of the keto acids had no effect on learning in the open-field task. In contrast, pretraining administration of KIV and KMV impaired habituation in the open field. Similarly, pretraining administration of KIC, KIV, and KMV affected rat performance in the inhibitory avoidance task, suggesting disruption of acquisition. The results indicate that the alpha-keto acids accumulating in MSUD induce learning deficits in aversive and nonaversive tasks. We therefore suggest that these findings may be related to the psychomotor delay/mental retardation observed in MSUD, and may indicate the contribution of increased brain concentrations of these organic acids to the pathophysiology of the neurological dysfunction of MSUD patients.

Animals↗