SEARCH · PubMed Health

Results for “Contrastive learning”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources

PubMed1994

Transient global amnesia following cerebral angiography with non-ionic contrast medium.

Transient global amnesia (TGA) is an uncommon syndrome of recent memory deficit and inability to learn new data, usually resolving within 24 h. Two cases following use of non-ionic contrast media in cerebral angiography are described. The neuroanatomy of memory is reviewed. Possible aetiologies of TGA in relation to cerebral angiography include ischaemia (embolic, arterial spasm), epilepsy that may be primary or tumour-related and direct toxic effects of contrast media.

Adult↗

PubMed1993

The development of curricular knowledge: a case of problematic pedagogical content knowledge during advanced knowledge acquisition.

The study examined what and how 12 K-8 physical education teacher education (PETE) majors learned about a movement approach that was discrepant from their experiences with physical education. This article describes one portion of the findings: what and how PETE majors learned about a movement approach to game play/strategy and mechanisms of advanced knowledge acquisition that contributed to confusion about this topic. Analytic induction and constant comparison were used to analyze qualitative data from interviews, observations, and relevant documents. Eleven PETE majors initially maintained partial or inaccurate conceptions about a movement approach to game play/strategy or taught this content in ways that were inconsistent with their goals for physical education, their knowledge about learning and teaching game skills, and the information presented by faculty and cooperating teachers. Interacting with students' prior knowledge and what and how faculty taught, the following learning mechanisms contributed to confusion: (a) overgeneralizing a contrast between a movement and traditional approach, (b) forming associations prior to adequate differentiation, and (c) overrelying on bottom-up thinking when initially developing lesson/unit progressions.

Curriculum↗

PubMed1992

Informativeness and the learning of bipolar adjectives.

The effects of informativeness upon the learning of bipolar adjectives were examined by asking 20 preschoolers to learn novel words descriptive of different lengths vs tensions of a coiled spring. The set of adjectives which contrasted most highly for informativeness showed the greatest asymmetry for successful learning.

Child, Preschool↗

PubMed1996

[Mentally handicapped and learning disordered co-workers in the occupational environment].

Attention is drawn to the specific issues faced--in contrast to other disability groups--in the vocational rehabilitation of persons with mental retardation and learning disorders. Current practice serves as a background for pointing out specific desiderations and outlining possible solutions. In particular posited is the need for a more tangible definition of modularized occupational qualifications as well as upgrading and refinement of flexible, community-based supports to be made available at the special/general labour market interface.

Education of Persons with Intellectual Disabilitie↗

PubMed2000

Effects of neonatal inferior prefrontal and medial temporal lesions on learning the rule for delayed nonmatching-to-sample.

The ability of rhesus monkeys to master the rule for delayed nonmatching-to-sample (DNMS) has a protracted ontogenetic development, reaching adult levels of proficiency around 4 to 5 years of age (Bachevalier, 1990). To test the possibility that this slow development could be due, at least in part, to immaturity of the prefrontal component of a temporo-prefrontal circuit important for DNMS rule learning (Kowalska, Bachevalier, & Mishkin, 1991; Weinstein, Saunders, & Mishkin, 1988), monkeys with neonatal lesions of the inferior prefrontal convexity were compared on DNMS with both normal controls and animals given neonatal lesions of the medial temporal lobe. Consistent with our previous results (Bachevalier & Mishkin, 1994; Málková, Mishkin, & Bachevalier, 1995), the neonatal medial temporal lesions led to marked impairment in rule learning (as well as in recognition memory with long delays and list lengths) at both 3 months and 2 years of age. By contrast, the neonatal inferior convexity lesions yielded no impairment in rule-learning at 3 months and only a mild impairment at 2 years, a finding that also contrasts sharply with the marked effects of the same lesion made in adulthood. This pattern of sparing closely resembles the one found earlier after neonatal lesions to the cortical visual area TE (Bachevalier & Mishkin, 1994; Málková et al., 1995). The functional sparing at 3 months probably reflects the fact that the temporo-prefrontal circuit is nonfunctional at this early age, resulting in a total dependency on medial temporal contributions to rule learning. With further development, however, this circuit begins to provide a supplementary route for learning.

Animals↗

PubMed1998

Physiological, pathophysiological and therapeutic roles of 5-HT systems in learning and memory.

Multiple 5-hydroxytryptamine (5-HT) receptors have been identified (5-HT1A/1B/1D/1E/1F, 5-HT2A/2B/2C, 5-HT3A/3B, 5-HT4A/4B, 5-HT5A/5B, 5-HT6 and 5-HT7A/7B/7C/7D) and extensive evidence suggests that 5-HT receptors have a role in learning and memory. Indeed, available evidence strongly supports physiological, pathophysiological and therapeutic roles of 5-HT systems in cognitive processes, although the evidence seems incomplete. Indeed, there has been a clear tendency to use pre-learning administration most frequently, whereas post-learning and pre-retention administration protocols have been utilized in only a few studies, and probably this trend has led to missed relevant information. For instance, when pre- vs post-training administration of 5-HT1A agonist, 5-HT2 antagonists and 5-HT4 agonists have been compared contrasting findings were reported in aversive and appetitive learning tasks. Emerging evidence also indicates that 5-HT1A and 5-HT4 receptor agonists, as well as, 5-HT1A antagonists, 5-HT2 antagonists, 5-HT3 antagonists and 5-HT uptake inhibitors may have therapeutic utility in the treatment of Alzheimer's disease and amnesia. Inasmuch as the activation or blockade of diverse 5-HT receptors is able to modulate cognitive processes, and 5-HT uptake inhibition could have therapeutic applications in the treatment of cognitive disorders, it seems evident that the role of 5-HT in learning and memory is more complex than a simple imbalance. Consequently, the notion that activation of the 5-HT systems impairs performance, whereas reduced serotonergic function may facilitate learning, must be reconsidered.

Animals↗

PubMed1990

Homicidal adolescents: a replication.

30 homicidal delinquents were matched with 30 nonviolent delinquents on age, race, sex, and socioeconomic status. Both groups received physical, psychological, educational, psychiatric and social examinations. Data were evaluated using stepwise discriminant analysis. Previous research was replicated. Homicidal adolescents shared four symptoms: criminally violent families, gang participation, alcohol abuse, severe learning difficulties. In addition, when the sample and the original group of murderers were combined the contrast between groups became clearer. Juvenile murderers lived in criminally violent families learning aggression during early childhood. Cognitive and perceptual deficits associated with epilepsy and central nervous system (CNS) conditions led to difficulties in the school years. During adolescence, gang participation and alcohol abuse added to earlier risk factors.

Adolescent↗

PubMed1994

Serial pattern learning after head injury.

Nonverbal serial pattern learning in patients with traumatic brain injury was examined using a serial reaction time task developed by Nissen and Bullemer (1987). During four blocks of pattern acquisition trials, subjects responded to asterisks appearing in repetitions of a 10-element spatial sequence. An indirect measure of pattern learning was obtained by comparing response times in the fourth pattern acquisition block with response times in a fifth block where asterisks occurred in random sequence. A direct measure of pattern memory was provided by accuracy scores in a final pattern generation block in which subjects predicted the spatial sequence of asterisks. Prior research with this task has shown that individuals from several special populations--including the normal elderly, Korsakoff's syndrome patients, and Alzheimer's patients--show intact performance on the indirect measure of pattern learning, but are impaired on the direct measure. In contrast to these earlier findings, the results of this study showed that mild to moderately severe traumatic brain injury does not cause a marked disruption in the ability to learn and remember serial pattern information. There was evidence that the amount of practice required to learn the serial pattern increases after moderately severe head injury; however, the ability to use pattern memory to enhance prediction accuracy appears to be normal.

Adolescent↗

PubMed1993

Constructive induction and protein tertiary structure prediction.

To date, the only methods that have been used successfully to predict protein structures have been based on identifying homologous proteins whose structures are known. However, such methods are limited by the fact that some proteins have similar structure but no significant sequence homology. We consider two ways of applying machine learning to facilitate protein structure prediction. We argue that a straightforward approach will not be able to improve the accuracy of classification achieved by clustering by alignment scores alone. In contrast, we present a novel constructive induction approach that learns better representations of amino acid sequences in terms of physical and chemical properties. Our learning method combines knowledge and search to shift the representation of sequences so that semantic similarity is more easily recognized by syntactic matching. Our approach promises not only to find new structural relationships among protein sequences, but also expands our understanding of the roles knowledge can play in learning via experience in this challenging domain.

Artificial Intelligence↗

PubMed2004

Nociceptin/orphanin FQ modulates spatial learning via ORL-1 receptors in the dorsal hippocampus of the rat.

The endogenous peptide nociceptin (orphanin FQ) plays a role in several important physiological functions in the CNS such as pain, anxiety and locomotion. It has previously been found that injection of 10 nmol nociceptin into the CA3 region of the hippocampus markedly impairs spatial learning and memory in the rat. The present study examined the effects of lower doses of nociceptin (3.3, 1, 0.33 and 0.1 nmol/rat) on spatial learning. The 3.3 nmol dose impaired spatial learning over the 5 days of training although the effect was not as strong as with 10 nmol. In contrast, the two lower doses, 1 and 0.33 nmol/rat, improved spatial learning whereas the lowest dose, 0.1 nmol/rat, had no significant effect. Both the impairing and facilitating effect of nociceptin could be blocked by an ORL-1 receptor antagonist, [Phe1Psi(CH(2)-NH)Gly2]NC(1-13)NH2 (10 nmol/rat), indicating that both effects are ORL-1 receptor-mediated. The 3.3 nmol dose of nociceptin did not impair the performance in the visual platform task and did not alter swim speed or motor activity indicating no effects on motivation or motor performance. Taken together, these results show that nociceptin has a biphasic dose-effect curve and provide further evidence for a role of this neuropeptide in cognitive processes in the hippocampus.

Animals↗

PubMed2006

Speech errors reflect newly learned phonotactic constraints.

Speech errors reveal the speaker's implicit knowledge of phonotactic constraints, both languagewide constraints (e.g., /K/ cannot be a syllable onset when one is speaking English) and experimentally induced constraints (e.g., /k/ cannot be an onset during the experiment). Four experiments investigated the acquisition of novel 2nd-order constraints, in which the allowable position of a consonant depends on some other property of the syllable (e.g., /k/ can only be an onset if the vowel is /I/). Participants recited strings of syllables that exhibited the novel constraints throughout a 4-day experiment. Their errors reflected the newly learned constraints but not until the 2nd day of training. This contrasts with previous research showing that errors become sensitive to 1st-order constraints almost immediately. A model that learns to assign phonemes to syllable positions is presented. It attributes the relative slowness of the acquisition of 2nd-order constraints to the self-interfering property of these constraints.

Humans↗

PubMed2003

Spatial and temporal sequence learning in patients with Parkinson's disease or cerebellar lesions.

The functional role of different subcortical areas in sequence learning is not clear. In the current study, Parkinson's patients, patients with cerebellar damage, and age-matched control participants performed a serial reaction time task in which a spatial sequence and a temporal sequence were presented simultaneously. The responses were based on the spatial sequence, and the temporal sequence was incidental to the task. The two sequences were of the same length, and the phase relationship between them was held constant throughout training. Sequence learning was assessed comparing performance when both sequences were present versus when the dimension of interest was randomized. In addition, sequence integration was assessed by introducing phase-shift blocks. A functional dissociation was found between the two patient groups. Whereas the Parkinson's patients learned the spatial and temporal sequences individually, they did not learn the relationship between the two sequences, suggesting the basal ganglia play a functional role in sequence integration. In contrast, the cerebellar patients did not show any evidence of sequence learning at all, suggesting the cerebellum might play a general role in forming sequential associations.

Aged↗

PubMed1995

Visual pattern memory without shape recognition.

Visual pattern memory of Drosophila melanogaster at the torque meter is investigated by a new learning paradigm called novelty choice. In this procedure the fly is first exposed to four identical patterns presented at the wall of the cylinder surrounding it. In the test it has the choice between two pairs of patterns, a new one and one the same as the training pattern. Flies show a lasting preference for the new figure. Figures presented during training are not recognized as familiar in the test, if displayed (i) at a different height, (ii) at a different size, (iii) rotated or (iv) after contrast reversal. No special invariance mechanisms are found. A pixel-by-pixel matching process is sufficient to explain the observed data. Minor transfer effects can be explained if a graded similarity function is assumed. Recognition depends upon the overlap between the stored template and the actual image. The similarity function is best described by the ratio of the area of overlap to the area of the actual image. The similarity function is independent of the geometrical properties of the employed figures. Visual pattern memory at this basic level does not require the analysis of shape.

Animals↗

PubMed2006

Short-term and long-term effects of violent media on aggression in children and adults.

OBJECTIVES: To test whether the results of the accumulated studies on media violence and aggressive behavior are consistent with the theories that have evolved to explain the effects. We tested for the existence of both short-term and long-term effects for aggressive behavior. We also tested the theory-driven hypothesis that short-term effects should be greater for adults and long-term effects should be greater for children. DESIGN: Meta-analysis. PARTICIPANTS: Children younger than 18 years and adults. MAIN EXPOSURES: Violent media, including TV, movies, video games, music, and comic books. MAIN OUTCOME MEASURES: Measures of aggressive behavior, aggressive thoughts, angry feelings, physiological arousal (eg, heart rate, blood pressure), and helping behavior. RESULTS: Effect size estimates were combined using meta-analytic procedures. As expected, the short-term effects of violent media were greater for adults than for children whereas the long-term effects were greater for children than for adults. The results also showed that there were overall modest but significant effect sizes for exposure to media violence on aggressive behaviors, aggressive thoughts, angry feelings, arousal levels, and helping behavior. CONCLUSIONS: The results are consistent with the theory that short-term effects are mostly due to the priming of existing well-encoded scripts, schemas, or beliefs, which adults have had more time to encode. In contrast, long-term effects require the learning (encoding) of scripts, schemas, or beliefs. Children can encode new scripts, schemas, and beliefs via observational learning with less interference and effort than adults.

Adult↗

PubMed1981

Genetic counseling: a comparison of counselee's genetic knowledge before and after (Part III).

Forty-seven mothers of children with Down syndrome were evaluated on their knowledge of genetic facts pertaining to Down syndrome. We found that more knowledge of this disorder was acquired by counselees before counseling than from counseling. The data show that counseling is most effective in enhancing counselees' knowledge of general genetics, ie, the origin of the extra chromosome in a child with Down syndrome. In contrast, counselees had the most difficulty in learning the recurrence risks for others, including the risks for relatives, siblings, and the population in general. A finding of practical importance is that formal education is inversely related to the amount of information counselees learned from counseling. Mothers with less than a high school education acquired most of their genetic knowledge from counseling, while those with more than a high school education acquired most of this information before counseling.

Down Syndrome↗

PubMedDate not supplied

Debias the environment instead of the judge: an alternative approach to reducing error in diagnostic (and other) judgment.

Questions about how to improve human judgment and reasoning are of theoretical and practical interest, notwithstanding the continuing controversy over whether people are "rational". Improving judgment may involve modifying people's processes to fit their environments better, or vice versa. We illustrate the latter approach in a study of diagnostic reasoning in which subjects learned to distinguish two fictitious diseases. Prior findings suggest that people may judge the likelihood of a diagnostic category on the presence or absence of features that are typical of, rather than diagnostic of, the category. We varied the structure of the information provided to subjects without attempting to modify their judgmental processes. In an "independent" format, subjects learned about each disease separately; in a "contrastive" format, information about the two diseases was juxtaposed to highlight distinctive features. Subjects in the two conditions formed different disease concepts. Diagnoses following contrastive training were much closer to the statistically prescribed judgments based on likelihood ratios. Interventions that modify the environment may provide an alternative approach where it is difficult to modify people's processes. Effective design of such interventions is one motivation for directing research toward understanding how task characteristics affect the use of and the outcomes of judgment and reasoning processes.

Adult↗

PubMed1991

Are eyeblink responses to tone in the decerebrate, decerebellate rabbit conditioned responses?

Bloedel and associates recently claimed to have established conditioned eyeblink responses in the acute decerebrate, decerebellate rabbit. Their training procedure was extreme massed practice (mean intertrial interval of 9 s) and they used an idiosyncratic definition of the conditioned response (10% or more of the unconditioned response amplitude). They did not measure or control the excitability of their preparations and did not run any separate control groups for alpha responses, alpha conditioning or pseudoconditioning. Using normal animals we compared their training procedure with procedures standard in the field and analyzed the consequences of their scoring procedure. Our group trained at a 30-s intertrial interval (ITI) showed clear learning in the training session. In marked contrast, 3 groups trained at a 9-s ITI developed no conditioned responses. We also found that the method of scoring used by Bloedel and associates counts many spontaneous responses as conditioned responses (CRs) if unconditioned response (UR) amplitudes are low, excludes genuine CRs if UR amplitudes are high and does not control for the occurrence of spontaneous responses. It must therefore be concluded that the eyeblink responses to tone reported by Bloedel and associates to occur in the decerebrate, decerebellate rabbit are not associative CRs as they develop in the normal animal.

Animals↗

PubMedDate not supplied

Promoting healthy weight: lessons learned from WIN the Rockies and other key studies.

In contrast to the traditional weight-centered approach, the Health At Every Size (HAES) or nondieting approach is health centered, with no focus on losing a predetermined amount of weight or fat. A key HAES principle of advocating healthy changes in food selection rather than adherence to prescriptive diets that involve calorie counting was adopted by Wellness in the Rockies (WIN the Rockies), a community-based research, intervention, and outreach project that promoted healthy lifestyles related to food, physical activity, and body image at the individual and community levels in Wyoming, Montana, and Idaho. The results from the project's cross-sectional surveys indicated that increased frequency of eating food while doing another activity, of drinking sweetened beverages such as soft drinks, and of consuming foods from fast-food restaurants were significant predictors of a high body mass index (BMI). In terms of energy expenditure, other predictors of high BMI from the WIN the Rockies cross-sectional surveys were lower frequency of participation in physical activity and the perception of not getting as much exercise as needed. The overall data provide support for the view that small diet- and physical activity-related lifestyle changes can cumulatively make a significant contribution to maintenance of healthy body weights. Although the community intervention emphasis of WIN the Rockies did not allow a specific assessment of the efficacy of HAES for individual participants in the project, this approach appears to hold great potential for promoting healthful lifestyle changes that improve quality of life.

Body Image↗