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PubMedDate not supplied

[Prenatal exposure to sodium oxybutyrate prevents a disorder of general behavior, learning and memory in the progeny of rats subjected to chronic hemic hypoxia].

The hemic hypoxia caused by the methemoglobin-inducing agent sodium nitrite (40 mg/kg intraperitoneally at days 10 to 19 of pregnancy) evokes a decrease in the birth and survival rates of pups, delayed disorders of motor coordination. Prenatal hypoxia was demonstrated to be able to disturb the habituation in the open field, learning and memory in passive avoidance paradigm, cognitive ability in the plus-maze extrapolative water escape test. The treatment of pregnant rats with sodium hydroxybutyrate (150 mg/kg orally 1-3 times daily at days 12 to 19 of pregnancy) normalizes offsprings' birth and survival rates, prevents the above-mentioned neuropsychological disturbances and improves learning in the active avoidance test.

Animals↗
PubMed1994

Do ability-performance relationships differentiate age and practice effects in visual search?

Relationships between abilities and performance in visual search were investigated for young and old adults. Ss received extensive practice on category search task. A consistent version allowed development of an automatic attention response; a varied version allowed general performance improvements. Transfer conditions assessed learning. General ability, induction, semantic knowledge, working memory, perceptual speed, semantic memory access, and psychomotor speed were assessed. LISREL models revealed that general ability and semantic memory access predicted initial performance for both ages. Improvements on both the consistent and varied tasks were predicted by perceptual speed. Ability-performance relationships indexed performance changes but were not predictive of learning (i.e., automatic process vs. general efficiency). Qualitative differences in the ability-transfer models suggest age differences in learning.

Adolescent↗
PubMed1999

Parents' experiences of general hospital admission for adults with learning disabilities.

General hospital care for people with learning disabilities is strongly emphasized in recent health policy. Ten sets of parents were interviewed about their experiences of general hospital inpatient care for their adult sons and daughters with learning disabilities. Findings in the areas of placement, occupation, basic nursing care, feeding, toileting, nursing attitudes, staffing and procedures are presented. Recommendations are made for changes to reported nursing practice to improve the quality of general hospital care for people with learning disabilities.

Adult↗
PubMed2006

Generalization of motor learning depends on the history of prior action.

Generalization of motor learning refers to our ability to apply what has been learned in one context to other contexts. When generalization is beneficial, it is termed transfer, and when it is detrimental, it is termed interference. Insight into the mechanism of generalization may be acquired from understanding why training transfers in some contexts but not others. However, identifying relevant contextual cues has proven surprisingly difficult, perhaps because the search has mainly been for cues that are explicit. We hypothesized instead that a relevant contextual cue is an implicit memory of action with a particular body part. To test this hypothesis we considered a task in which participants learned to control motion of a cursor under visuomotor rotation in two contexts: by moving their hand through motion of their shoulder and elbow, or through motion of their wrist. Use of these contextual cues led to three observations: First, in naive participants, learning in the wrist context was much faster than in the arm context. Second, generalization was asymmetric so that arm training benefited subsequent wrist training, but not vice versa. Third, in people who had prior wrist training, generalization from the arm to the wrist was blocked. That is, prior wrist training appeared to prevent both the interference and transfer that subsequent arm training should have caused. To explain the data, we posited that the learner collected statistics of contextual history: all upper arm movements also move the hand, but occasionally we move our hands without moving the upper arm. In a Bayesian framework, history of limb segment use strongly affects parameter uncertainty, which is a measure of the covariance of the contextual cues. This simple Bayesian prior dictated a generalization pattern that largely reproduced all three findings. For motor learning, generalization depends on context, which is determined by the statistics of how we have previously used the various parts of our limbs.

Adult↗
PubMed2006

Parameter learning from stochastic teachers and stochastic compulsive liars.

This paper considers a general learning problem akin to the field of learning automata (LA) in which the learning mechanism attempts to learn from a stochastic teacher or a stochastic compulsive liar. More specifically, unlike the traditional LA model in which LA attempts to learn the optimal action offered by the Environment (also here called the "Oracle"), this paper considers the problem of the learning mechanism (robot, an LA, or in general, an algorithm) attempting to learn a "parameter" within a closed interval. The problem is modeled as follows: The learning mechanism is trying to locate an unknown point on a real interval by interacting with a stochastic Environment through a series of informed guesses. For each guess, the Environment essentially informs the mechanism, possibly erroneously (i.e., with probability p), which way it should move to reach the unknown point. When the probability of a correct response is p > 0.5, the Environment is said to be informative, and thus the case of learning from a stochastic teacher. When this probability p < 0.5, the Environment is deemed deceptive, and is called a stochastic compulsive liar. This paper describes a novel learning strategy by which the unknown parameter can be learned in both environments. These results are the first reported results, which are applicable to the latter scenario. The most significant contribution of this paper is that the proposed scheme is shown to operate equally well, even when the learning mechanism is unaware of whether the Environment ("Oracle") is informative or deceptive. The learning strategy proposed herein, called CPL-AdS, partitions the search interval into d subintervals, evaluates the location of the unknown point with respect to these subintervals using fast-converging E-optimal LRI LA, and prunes the search space in each iteration by eliminating at least one partition. The CPL-AdS algorithm is shown to provably converge to the unknown point with an arbitrary degree of accuracy with probability as close to unity as desired. Comprehensive experimental results confirm the fast and accurate convergence of the search for a wide range of values for the Environment's feedback accuracy parameter p, and thus has numerous potential applications.

Algorithms↗
PubMed1999

Syllable onsets: clusters and adjuncts in acquisition.

The Sonority Sequencing Principle is a presumed universal that governs the permissible sequences of consonants within syllables. In two single-subject experiments, we evaluated this principle as applied to the acquisition of onset clusters and adjuncts by children exhibiting functional phonological delays (age in years;months: 3;2 to 7;8). Experiment 1 tested the hypothesis that children abide by the Sonority Sequencing Principle in development, such that the occurrence and use of marked true clusters implies unmarked clusters, but not vice versa. This claim was validated, in part, by the gradient generalization learning patterns of children who were taught marked clusters. Others who were taught unmarked clusters exhibited limited learning characteristic of within-class generalization, with apparent gaps in sonority sequencing. Experiment 2 examined the role of adjunct sequences /sp, st, sk/, whose markedness status is questionable given their violation of the Sonority Sequencing Principle. Results indicated that children learned adjuncts consistent with patterns of within-class generalization, thereby supporting the view that these sequences are unmarked in structure. Experimental findings are integrated in discussion of the representation of onset clusters and their course of emergence in phonological acquisition relative to the Sonority Sequencing Principle.

Articulation Disorders↗
PubMed2006

Implicit learning and statistical learning: one phenomenon, two approaches.

The domain-general learning mechanisms elicited in incidental learning situations are of potential interest in many research fields, including language acquisition, object knowledge formation and motor learning. They have been the focus of studies on implicit learning for nearly 40 years. Stemming from a different research tradition, studies on statistical learning carried out in the past 10 years after the seminal studies by Saffran and collaborators, appear to be closely related, and the similarity between the two approaches is strengthened further by their recent evolution. However, implicit learning and statistical learning research favor different interpretations, focusing on the formation of chunks and statistical computations, respectively. We examine these differing approaches and suggest that this divergence opens up a major theoretical challenge for future studies.

Attention↗
PubMed2006

Generalization in perceptual learning for speech.

Lexical context strongly influences listeners' identification of ambiguous sounds. For example, a sound midway between /f/ and /s/ is reported as /f/ in "sheri_," but as /s/ in "Pari_." Norris, McQueen, and Cutler (2003) have demonstrated that after hearing such lexically determined phonemes, listeners expand their phonemic categories to include more ambiguous tokens than before. We tested whether listeners adjust their phonemic categories for a specific speaker. Do listeners learn a particular speaker's "accent"? Similarly, we examined whether perceptual learning is specific to the particular ambiguous phonemes that listeners hear, or whether the adjustments generalize to related sounds. Participants heard ambiguous /d/ or /t/ phonemes during a lexical decision task. They then categorized sounds on /d/-/t/ and /b/-/p/ continua, either in the same voice that they had heard for lexical decision, or in a different voice. Perceptual learning generalized across both speaker and test continua: Changes in perceptual representations are robust and broadly tuned.

Decision Making↗
PubMed1993

Continuing education for general practice. 1. Experience, competence and the media of self-directed learning for established general practitioners.

The arrangements under which continuing education for general practice is provided and attendance by general practitioners is rewarded have now been in operation for three years. More recently, reaccreditation has emerged as a significant issue for the profession. For these reasons it appears timely to review the whole basis of ongoing learning by established general practitioners. In this the first of two papers, learning by established professionals is considered in relation to the educational development of the learner, the role of experience and the goals of competence and performance. It is concluded that self-directed learning based on experience should form the centre-piece of continuing education for general practice and that educational provision should adopt a complementary role in sustaining motivation to learn and by enabling learning from experience to be shared and enriched. A model of self-directed learning, connecting experience and competence through systematic application of three learning media, reading, reflection and audit, is proposed and related to appropriate educational participation by established general practitioners.

Clinical Competence↗
PubMed2001

Incremental projection learning for optimal generalization.

In many practical situations in neural network learning, it is often expected to further improve the generalization capability after the learning process has been completed. One of the common approaches is to add training data to the neural network. In view of the learning methods of human beings, it seems natural to build posterior learning results upon prior results, which is generally referred to as incremental learning. Many incremental learning methods have been devised so far. However, they provide poor generalization capability compared with batch learning methods. In this paper, a method of incremental projection learning in the presence of noise is presented, which provides exactly the same learning result as that obtained by batch projection learning. The effectiveness of the presented method is demonstrated through computer simulations.

Humans↗
PubMed2000

Mechanisms of generalization in perceptual learning.

Learning in many visual perceptual tasks has been shown to be specific to practiced stimuli, while new stimuli have to be learned from scratch. Here we demonstrate generalization using a novel paradigm in motion discrimination where learning has been previously shown to be specific. We trained subjects to discriminate directions of moving dots, and verified the previous results that learning does not transfer from a trained direction to a new one. However, by tracking the subjects' performance across time in the new direction, we found that their speed of learning doubled. Therefore, we found generalization in a task previously considered too difficult to generalize. We also replicated, in a second experiment, transfer following training with 'easy' stimuli, when the difference between motion directions is enlarged. In a third experiment we found a new mode of generalization: after mastering the task with an easy stimulus, subjects who have practiced briefly to discriminate the easy stimulus in a new direction generalize to a difficult stimulus in that direction. This generalization depends on both the mastering and the brief practice. The specificity of perceptual learning and the dichotomy between learning of 'easy' versus 'difficult' tasks have been assumed to involve different learning processes at different cortical areas. Here we show how to interpret these results in terms of signal detection theory. With the assumption of limited computational capacity, we obtain the observed phenomena--direct transfer and acceleration of learning--for increasing levels of task difficulty. Human perceptual learning and generalization, therefore, concur with a generic discrimination system.

Discrimination, Psychological↗