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At least 613 records · Page 34Linked to original sources
PubMed1998

Abstraction is impaired at the perceptual level in schizophrenic patients.

This study investigates category learning in schizophrenia in order to evaluate abstraction abilities at the perceptual level. The participants learned about two categories of geometric shapes. The category exemplars were presented successively. In the case of schizophrenic patients, longer exposure time and more stimulus presentations were used to counterbalance attention impairments. In spite of this, the perceptual category learning was significantly impaired in the patient group. In contrast, when the training procedure involved verbal category definition and not perceptual learning, the performance of schizophrenics was similar to that of the healthy controls. These findings suggest that the perceptual learning of categories, but not free classification judgements are impaired in schizophrenia, and that this impairment is not due to pure attentional disturbances.

Adult↗
PubMed1997

Recognition and treatment of reactions to contrast media: a model for resident and faculty education employing lectures and case scenario workshops.

RATIONALE AND OBJECTIVES: The effectiveness of an interactive course on the recognition and treatment of contrast media reactions was studied. METHODS: An instructional course on contrast media reactions was organized for the radiology staff, residents, and nurses. Before the beginning of the 3-day course, a 25-point pretest was administered to determine the ability of each participant to recognize and treat contrast material reactions. An identical posttest was administered after the course, and the pre- and posttest results were compared. RESULTS: There was a statistically significant improvement on the posttest scores for all subjects tested (P < .05). There was also a substantial improvement in the participants' confidence levels in dealing with contrast media reactions. CONCLUSIONS: A short course on contrast material reactions is a worthwhile learning aid that is simple to conduct and educates and instills confidence in both residents and staff.

Contrast Media↗
PubMed2005

Processing content or location: distinct brain activation in a memory task.

Objects are defined by their content ("what") and by their location ("where"). In the visual system, processing of these two types of information is segregated into distinct anatomical and functional pathways. Using H2 (15)O positron emission tomography to measure cerebral blood flow, we examined the differences in processing of "what" when compared with "where" information in human memory. We found that the detection of deviations from a previously learned image sequence activates distinct brain regions depending on whether the image's content or its location has changed. When deviations of an image's content had to be detected, the left medial temporal lobe (MTL) activation increased. In contrast, detection of deviations from the learned locations of the objects induced increased activation in the right MTL and in the right parietal cortex. These data demonstrate distinct contributions of the left and right MTL to the processing of "what" vs. "where" in memory.

Adult↗
PubMed1986

Reversal and nonreversal shifts under amphetamine.

Rats were trained in a Y maze on a two-choice simultaneous brightness discrimination with light as S+ and dark as S- (position irrelevant). Half of the animals were then switched to reversal, where the reinforcement contingencies of the original training were reversed, and the other half were switched to nonreversal, in which they learned a simultaneous right-left discrimination. Nonreversal was acquired faster than reversal in saline injected animals. The administration of 1 mg/kg d-amphetamine did not affect the acquisition of the initial brightness discrimination and of nonreversal. In contrast, the drug facilitated dramatically reversal learning. The results indicate that amphetamine enhances the attention to, or the associability of, the discriminative stimuli, leading to rapid learning to these stimuli under changed contingencies of reinforcement.

Animals↗
PubMed1996

Contrasting effects of fetal CA1 and CA3 hippocampal grafts on deficits in spatial learning and working memory induced by global cerebral ischaemia in rats.

Functional effects of fetal hippocampal field grafts were assessed in rats with spatial learning and memory impairments following global cerebral ischaemia. Experiment 1 examined effects of grafts dissected from fields CA1 and CA3 at embryonic day 19 and from the dentate gyrus at postnatal day 1. Cell suspensions (15,000 cells/site) were implanted bilaterally at two points above the dorsal CA1 area two weeks after four-vessel occlusion (electrocoagulation of the vertebral arteries followed the 24 h later by occlusion of the carotid arteries for 15 min). Histological examination showed that CA1 neuronal loss (60-70%) was equivalent in all ischaemic groups and that 80% of CA1 and 60% of CA3 grafts survived and were sited appropriately in the alveus or corpus callosum above the area of ischaemic CA1 damage in the host, but there was no survival of dentate grafts. Results from rats with poor pyramidal cell graft survival were excluded, but those from rats with non-surviving dentate grafts were retained as an additional control group. Acquisition in the water maze was examined nine and 25 weeks after transplantation, and spatial working memory was assessed in three-door runway and water maze matching-to-position tasks 19 and 28 weeks after grafting, respectively. For water maze acquisition rats were trained with two trails/day and a 10 min inter-trial interval for 10-12 days to locate a submerged platform. Ischaemic rats with CA1 grafts learned the platform position as rapidly as non-ischaemic controls, searched appropriately in the training quadrant and were accurate in heading towards the platform, but were initially impaired on recall of the precise platform position on probe trials with the platform removed. Performance of ischaemic controls and groups with CA3 and non-surviving dentate graft groups was significantly impaired relative to controls and to the CA1 grafted group. The CA1 grafted group was also as successful as controls in matching-to-position in the water maze and substantially superior to the other ischaemic groups, assessed using three trials/day, with a 30-s inter-trial interval and a different platform position on each day. In a more complex matching-to-position task in the three-door runway, the performance of the CA1 grafted group was significantly impaired relative to controls, although superior to that of the other ischaemic control and graft groups. Functional recovery with CA1, but not CA3, grafts in ischaemic rats was replicated in a second experiment which assessed water maze acquisition and working memory at 10 and 14 weeks after transplantation, in rats with 90% graft survival. These results indicate that long-lasting, task-dependent improvements can be seen in ischaemic rats with CA1 fetal grafts in both aversively and appetitively motivated spatial learning tasks. The findings suggest that functional recovery requires homotypic replacement of CA1 cells damaged by ischaemia, rather than provision of structurally similar glutamate-releasing CA3 pyramidal cells.

Animals↗
PubMed2003

Infant perception of non-native consonant contrasts that adults assimilate in different ways.

Numerous findings suggest that non-native speech perception undergoes dramatic changes before the infant's first birthday. Yet the nature and cause of these changes remain uncertain. We evaluated the predictions of several theoretical accounts of developmental change in infants' perception of non-native consonant contrasts. Experiment 1 assessed English-learning infants' discrimination of three isiZulu distinctions that American adults had categorized and discriminated quite differently, consistent with the Perceptual Assimilation Model (PAM: Best, 1995; Best et al., 1988). All involved a distinction employing a single articulatory organ, in this case the larynx. Consistent with all theoretical accounts, 6-8 month olds discriminated all contrasts. However, 10-12 month olds performed more poorly on each, consistent with the Articulatory-Organ-matching hypothesis (AO) derived from PAM and Articulatory Phonology (Studdert-Kennedy & Goldstein, 2003), specifically that older infants should show a decline for non-native distinctions involving a single articulatory organ. However, the results may also be open to other interpretations. The converse AO hypothesis, that non-native between-organ distinctions will remain highly discriminable to older infants, was tested in Experiment 2, using a non-native Tigrinya distinction involving lips versus tongue tip. Both ages discriminated this between-organ contrast well, further supporting the AO hypothesis. Implications for theoretical accounts of infant speech perception are discussed.

Discrimination Learning↗
PubMed2025

Learning neural dynamics through instructive signals.

Rapid learning is essential for flexible behavior, but its basis in the brain remains unknown. Here we introduce the PRISM plasticity rule, a unifying mechanistic model of three well-established, fast-acting synaptic plasticity rules-in hippocampus, cerebellum and mushroom body-which relies exclusively on pre-synaptic activity and an "instructive signal" from another brain area. Using a multi-region network model we show that guiding PRISM plasticity with instructive signals enables the network to quickly learn extremely flexible nonlinear dynamics underlying behaviorally relevant computations, as well as to emulate unknown external system dynamics from real-time error signals, which we demonstrate with comprehensive simulations supported by exact mathematical theory. Thus, PRISM plasticity guided by instructive signals is well-suited to rapidly learn general-purpose neural computations-in contrast to canonical Hebbian rules. Finally, we show how including this plasticity rule in artificial learning algorithms can solve long-range temporal credit assignment, a long-standing challenge in machine learning.

cerebellum↗
PubMed1988

Beyond career choice: the role of learning style analysis in residency training.

A recent article in this journal took an important step toward rethinking the utility of behavioural instruments designated as learning style tests (Jewett et al. 1987). The authors of that paper made much of a distinction between the terms 'learning style' and 'learning preference'. However, the results of their study do not seem to substantiate a marked difference between the function of the Rezler Learning Preference Inventory (LPI) and Kolb's Learning Style Inventory (LSI) with which it was contrasted. The most important aspect of their paper was that it rescued the concept of learning style analysis from the arena of career choice prediction at the undergraduate level and applied these ideas to doctors who had already made their specialty selections and were actively engaged in residency training. Clinical instructors in teaching institutions have, for the most part, little or no formal background in educational principles. For these individuals, an easily comprehensible model of resident-instructor psychology can be very useful on a daily basis. This article reviews the authors' experience with the LSI and describes their utilization of Kolb's Experimental Learning Model in the areas of resident counselling and residency curriculum design. The results of two recent studies are also presented in which learning style was examined as a predictor of success in residency, and teacher-resident learning style distributions were shown to exhibit parallel relationships at four different anaesthesiology residency training programmes.

Anesthesiology↗
PubMed1996

A neostriatal habit learning system in humans.

Amnesic patients and nondemented patients with Parkinson's disease were given a probabilistic classification task in which they learned which of two outcomes would occur on each trial, given the particular combination of cues that appeared. Amnesic patients exhibited normal learning of the task but had severely impaired declarative memory for the training episode. In contrast, patients with Parkinson's disease failed to learn the probabilistic classification task, despite having intact memory for the training episode. This double dissociation shows that the limbic-diencephalic regions damaged in amnesia and the neostriatum damaged in Parkinson's disease support separate and parallel learning systems. In humans, the neostriatum (caudate nucleus and putamen) is essential for the gradual, incremental learning of associations that is characteristic of habit learning. The neostriatum is important not just for motor behavior and motor learning but also for acquiring nonmotor dispositions and tendencies that depend on new associations.

Aged↗
PubMed1987

Learning and using specific instances.

A biologically plausible method for rapidly learning specific instances is described. It is contrasted with a formal model of classical conditioning (Rescorla-Wagner learning/perception training), which is shown to be relatively good for learning generalizations, but correspondingly poor for learning specific instances. A number of behaviorally relevant applications of specific instance learning are considered. For category learning, various combinations of specific instance learning and generalization are described and analyzed. Two general approaches are considered: the simple inclusion of Specific Instance Detectors (SIDs) as additional features during perception training, and specialized treatment in which SID-based categorization takes precedence over generalization-based categorization. Using the first approach, analysis and empirical results demonstrate a potential problem in representing feature presence and absence in a symmetric fashion when the frequencies of feature presence and absence are very different. However, it is shown that by using the proper representation, the addition of SIDs can only improve the convergence rate of perceptron training, the greatest improvement being achieved when SIDs are preferentially allocated for peripheral positive and negative instances. Some further improvement is possible if SIDs are treated in a specialized manner.

Animals↗
PubMed1994

Effects of (R)-alpha-methylhistamine and scopolamine on spatial learning in the rat assessed using a water maze.

The effects of (R)-alpha-methylhistamine ((R)-alpha-MeHA, a selective H3-receptor agonist) and scopolamine (SCOP, a muscarinic antagonist) were investigated on spatial learning and memory in the rat (Hooded Lister) using a water maze (WM). (R)-alpha-MeHA treatment (6.3 and 10 mg/kg IP) had no apparent effect on spatial learning but did result in enhanced spatial recall at the higher dose, assessed by a transfer (probe) test after training. In contrast, SCOP (0.5 mg/kg IP) induced a learning and memory deficit measured both during and after training. In animals treated with (R)-alpha-MeHA and SCOP, (R)-alpha-MeHA partially (6.3 mg/kg) and completely (10 mg/kg) reversed the SCOP-induced deficit during the training phase, while in the post-training transfer test, (R)-alpha-MeHA (10 mg/kg) significantly reduced the SCOP-induced memory deficit. None of the treatments described resulted in impaired visual acuity as demonstrated by a raised platform test. These results are consistent with a role for histamine in cognitive processes and suggest a possible interaction between central histamine and cholinergic mechanisms associated with rodent spatial learning and memory.

Animals↗
PubMed2005

Antennal tactile learning in the honeybee: effect of nicotinic antagonists on memory dynamics.

Restrained worker honeybees (Apis mellifera L.) are able to learn to associate antennal-scanning of a metal plate with a sucrose reinforcement delivered to the mouthparts. Learning occurs reliably in a single association of the two sensory stimuli. The involvement of nicotinic pathways in memory formation and retrieval processes was tested by injecting, into the whole brain through the median ocellus, either mecamylamine (0.6 microg per bee) or alpha-bungarotoxin (2.4 ng per bee). Saline served as a control. Mecamylamine injected 10 min before the retrieval test impairs the retention level tested 3 h and 24 h after single- or multi-trial learning. Retrieval tests performed at various times after the injection show that the blocking effect of mecamylamine lasts about 1 h. The drug has no effect on the reconsolidation or extinction processes. Mecamylamine injected 10 min before conditioning impairs single-trial learning but has no effect on five-trial learning and on the consolidation process. By contrast, alpha-bungarotoxin only impairs the formation of long-term memory (24 h) induced by the five-trial learning and has no effect on medium-term memory (3 h), on single-trial learning or on the retrieval process. Hence, owing to previous data, at least two kinds of nicotinic receptors seem to be involved in honeybee memory, an alpha-bungarotoxin-sensitive and an alpha-bungarotoxin-insensitive receptor. Our results extend to antennal mechanosensory conditioning the role of the cholinergic system that we had previously described for olfactory conditioning in the honeybee. Moreover, we describe here in this insect a pharmacological dissociation between alpha-bungarotoxin sensitive long-term memory and alpha-bungarotoxin insensitive medium-term memory, the last one being affected by mecamylamine.

Animals↗
PubMed2003

Category use and category learning.

Categorization models based on laboratory research focus on a narrower range of explanatory constructs than appears necessary for explaining the structure of natural categories. This mismatch is caused by the reliance on classification as the basis of laboratory studies. Category representations are formed in the process of interacting with category members. Thus, laboratory studies must explore a range of category uses. The authors review the effects of a variety of category uses on category learning. First, there is an extensive discussion contrasting classification with a predictive inference task that is formally equivalent to classification but leads to a very different pattern of learning. Then, research on the effects of problem solving, communication, and combining inference and classification is reviewed.

Classification↗
PubMed2005

Discrimination training of phonemic contrasts enhances phonological processing in mainstream school children.

Auditory perceptual learning has been proposed as effective for remediating impaired language and for enhancing normal language development. We examined the effect of phonemic contrast discrimination training on the discrimination of whole words and on phonological awareness in 8- to 10-year-old mainstream school children. Eleven phonemic contrast continua were synthesised using linear interpolation coding from real speaker endpoints. Thirty children were pre-tested on the Word Discrimination Test (WDT) and the Phonological Assessment Battery (PhAB). Eighteen then trained for 12 x 30min sessions over 4 weeks using an adaptive three interval two alternative phonemic matching task. The remaining children participated in regular classroom activities. In Post-testing, trained children significantly increased their age-equivalent scores on both the WDT and PhAB by about 2 years. For the PhAB, no improvement was found in the controls. Enhanced performance in the trained children was maintained in a delayed test 5-6 weeks following training. Enhancements on the trained discriminations were weak and variable. The results indicate a dramatic improvement in phonological awareness following phonemic discrimination training without matching perceptual learning.

Child↗
PubMed2006

Radiology curriculum for medical students: clinicians' perspectives.

This study was conducted to establish clinicians' perspectives of a set of radiology curriculum topics for medical student teaching, which were held to be important by radiologists. A questionnaire was sent to clinicians in all specialties. Forty-six clinicians (51.1%) out of 90 returned the questionnaires. All curriculum topics were scored above an average of 4 (agree). The five highest ranking curriculum topics in order of importance were: developing a system for viewing chest radiographs (5.59), developing a system for viewing abdominal radiographs (5.56), developing a system for viewing bone and joint radiographs (5.33), distinguishing normal structures from abnormal in chest and abdominal radiographs (5.33) and identifying gross bone or joint abnormalities in skeletal radiographs (5.22). Correlative analysis between speciality groups showed surgical and medical specialities were significantly different in their responses of two learning outcomes: basic knowledge about the contrast media benefits and risks (P= 0.01) and ability to select the most appropriate and the most cost-effective methods of radiological investigations for clinical situations (P= 0.03). Acute specialities were not significantly different from the other two groups for these two learning outcomes. There was no statistically significant difference for other learning outcomes between the three speciality groups.

Curriculum↗
PubMed2006

Probabilistic fusion of stereo with color and contrast for bilayer segmentation.

This paper describes models and algorithms for the real-time segmentation of foreground from background layers in stereo video sequences. Automatic separation of layers from color/contrast or from stereo alone is known to be error-prone. Here, color, contrast, and stereo matching information are fused to infer layers accurately and efficiently. The first algorithm, Layered Dynamic Programming (LDP), solves stereo in an extended six-state space that represents both foreground/background layers and occluded regions. The stereo-match likelihood is then fused with a contrast-sensitive color model that is learned on-the-fly and stereo disparities are obtained by dynamic programming. The second algorithm, Layered Graph Cut (LGC), does not directly solve stereo. Instead, the stereo match likelihood is marginalized over disparities to evaluate foreground and background hypotheses and then fused with a contrast-sensitive color model like the one used in LDP. Segmentation is solved efficiently by ternary graph cut. Both algorithms are evaluated with respect to ground truth data and found to have similar performance, substantially better than either stereo or color/ contrast alone. However, their characteristics with respect to computational efficiency are rather different. The algorithms are demonstrated in the application of background substitution and shown to give good quality composite video output.

Algorithms↗
PubMedDate not supplied

Prenatal phenytoin exposure and spatial navigation in offspring: effects on reference and working memory and on discrimination learning.

Previous research has shown that rats exposed to phenytoin (PHT) in utero demonstrate abnormal circling, decreased learning, hyperactivity, and delayed air righting reflex development. The effects of prenatal PHT on offspring learning have been found on multiple-T mazes (Biel and Cincinnati types) and on spatial navigation (Morris maze). However, the specificity of the latter effects is unknown. Herein, we tested the effects of prenatal PHT in a Morris maze using six different procedures: cued versus spatial reference memory-based learning, cued versus spatial working memory-based learning, and cued versus spatial discrimination learning. PHT-exposed offspring showed increased preweaning mortality, growth reduction, and abnormal circling as noted in previous studies. PHT offspring were separated into those exhibiting circling and those not. PHT noncircling offspring demonstrated impaired reference memory-based spatial learning (acquisition and reversal), but no other effects. By contrast, PHT circling offspring demonstrated not only impaired reference memory-based spatial learning, but also impaired cued platform learning, impaired spatial discrimination, and impaired working memory-based learning. These data confirm that prenatal PHT induces a specific reference memory-based spatial learning deficit even in asymptomatic (noncircling) offspring that is distinct from the impairment induced in littermates exhibiting the circling impairment.

Analysis of Variance↗