Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Probability Learning”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,423 records · Page 79Linked to original sources
PubMed1996

Varieties of Helmholtz Machine.

The Helmholtz machine is a new unsupervised learning architecture that uses top-down connections to build probability density models of input and bottom-up connections to build inverses to those models. The wake-sleep learning algorithm for the machine involves just the purely local delta rule. This paper suggests a number of different varieties of Helmholtz machines, each with its own strengths and weaknesses, and relates them to cortical information processing. Copyright 1996 Elsevier Science Ltd.

Journal Article↗
PubMed1999

Stress impairs performance in spatial water maze learning tasks.

The water maze task has been developed to test spatial learning abilities in rats or mice, and is widely used. Though it has been reported before that numerous cognitive abilities are of importance for learning this task, poor performance is usually interpreted as an impairment of spatial memory formation. Previous investigations that tried to correlate long-term potentiation (LTP) of synaptic transmission with spatial learning abilities in rats reported that injection of drugs or specific gene deletions which blocked the expression of LTP correlated with learning impairments of spatial tasks in a water maze. Recent studies, however, have shown that pretraining enables these animals to learn such spatial tasks even though LTP was still found to be blocked. I investigated to what degree altered fear condition and stress perception could account for the impaired spatial learning when no pretraining is given. In a fear habituation task, unhandled rats preferred a dark over a well lit chamber more than handled animals did, but unhandled rats favoured the lit chamber more in an active avoidance task. They also performed poorly in a spatial water maze task compared with handled rats. Rats pretrained in a radial arm maze performed better in a water maze than non-pretrained rats. No difference between groups was found in a non-spatial water maze task. On the other hand, when pretrained in a water maze, rats performed only marginally better in a radial arm maze compared to non-pretrained animals. Since animals have to be handled to learn a radial arm maze, the difference in this task was not due to stress but most probably due to getting accustomed to the room dimensions prior to learning the spatial task. The results suggest that impaired learning of spatial tasks in the water maze can be due to increased stress and decreased fear conditioning without actually affecting spatial learning abilities. These results question the interpretations of the results of some previously published results of spatial water maze tasks.

Animals↗
PubMed2006

The problem of reversals in assessing implicit sequence learning with serial reaction time tasks.

We report two experiments in which implicit learning is demonstrated within a short session of practice, in the absence of explicit knowledge of what is learned. In Experiment 1, we replicate the experiments by Curran (Psychol Res 60:24-41, 1997a; J Cogn Neurosci 9(4):522-533, 1997b) and highlight the importance of avoiding a random sequence as comparison to the training sequence, due to the higher proportion of reversal trials included in the random one, which leads to an artifactual measure of learning. In Experiment 2 we present a procedure in which two structurally analogous sequences are used both as training and control sequences, thus controlling for any factor different from learning. The results show that implicit learning is obtained within a short session of practice, and in the absence of any explicit knowledge as assessed through a subsequent generation task. We surmise that this procedure might be especially useful in areas in which short procedures are needed, such as when special populations are tested (e.g., patients, children or elderly people) or when the neural bases of implicit learning are being investigated through neurophysiological measures.

Analysis of Variance↗
PubMedDate not supplied

Cognitive processes and cognitive progresses as didactic tools in psychiatry.

The authors expose the characteristics of two methods about the teaching and the learning of Psychiatry. Hermeneutic method is based on the model: "this want to say that". It gives rise to rapid and diffused learning which are rarely personalized and it attributes activity to the teacher and passivity to the pupil. "Conjectural" method is based on the model: "this is one of the aspects of a polymer of significances that we may point out as probable conjecture and not as truth". It produces learning less rapid, less diffused but more personal. It attributes activity and passivity as to the teacher as to the pupil. The first method tends to provoke pathological dependence as proselitism and/or contest so the pupil difficulty may assume the heritage of the teacher by having idealized or killed him. The second method tends to form self-governing pupils able to break away from the teacher after having learned from him new knowledges which they use in a personal way.

Humans↗
PubMed1994

Attention deficit disorder in children: three clinical variants.

A clinic-referred population of 116 children with attentional problems was classified by DSM-III [attention deficit disorder (ADD)] with respect to inattention, impulsivity, and hyperactivity. The sample proved to subdivide into three groups: inattentive, impulsive, and hyperactive (HII), n = 60; inattentive and impulsive (II), n = 26; and inattentive (I), n = 30. The distinction between II and I resolves the confounding of impulsivity and inattention in previous studies of children who have ADD but are not hyperactive. The three groups were found to be similar in mean age, gender ratio, prevalence, and pattern of associated learning disabilities, family history of psychopathology, and probability of favorable response to methylphenidate. Group I differed from Groups HII and II in the frequency of externalizing relative to internalizing comorbid psychopathology. A group that is hyperactive and impulsive but not inattentive was not found. The preponderance of similarities in associated characteristics suggests that the three groups are differing clinical presentations of an ADD spectrum.

Adolescent↗
PubMed1988

Learning in mature mice (Peromyscus leucopus) subjected to deep hypothermia as neonates.

In certain species of nonhibernating rodents, although young nestlings cease breathing and heart action when their body temperature is lowered to near freezing, the nestlings need only be rewarmed to recover. This remarkable capacity for immediate recovery has been known many years, but long-range consequences of deep neonatal hypothermia have never before been investigated. Mice (Peromyscus leucopus) that had been exposed to four 2.5-hr episodes of deep (2-4 degrees C) hypothermia when 4-10 days old were later compared with littermate controls in their performance on two learning tasks. The two groups did not differ in their acquisition or extinction of a lithium-induced learned taste aversion to sucrose. Nor did they differ in learning to find a hidden platform in a swimming pool. Thus in a nonhibernating rodent species, deep hypothermia experienced neonatally--unlike similar hypothermia administered in adulthood--seems not to induce deficits in subsequent learning capabilities. The resistance of neonates to damage probably represents an adaptation, for their modest thermoregulatory abilities render them vulnerable to deep hypothermia in frigid environments.

Animals↗
PubMed2004

A neural correlate of reward-based behavioral learning in caudate nucleus: a functional magnetic resonance imaging study of a stochastic decision task.

Humans can acquire appropriate behaviors that maximize rewards on a trial-and-error basis. Recent electrophysiological and imaging studies have demonstrated that neural activity in the midbrain and ventral striatum encodes the error of reward prediction. However, it is yet to be examined whether the striatum is the main locus of reward-based behavioral learning. To address this, we conducted functional magnetic resonance imaging (fMRI) of a stochastic decision task involving monetary rewards, in which subjects had to learn behaviors involving different task difficulties that were controlled by probability. We performed a correlation analysis of fMRI data by using the explanatory variables derived from subject behaviors. We found that activity in the caudate nucleus was correlated with short-term reward and, furthermore, paralleled the magnitude of a subject's behavioral change during learning. In addition, we confirmed that this parallelism between learning and activity in the caudate nucleus is robustly maintained even when we vary task difficulty by controlling the probability. These findings suggest that the caudate nucleus is one of the main loci for reward-based behavioral learning.

Adult↗
PubMed2001

Expression of protein kinase C inhibitor blocks cerebellar long-term depression without affecting Purkinje cell excitability in alert mice.

A longstanding but still controversial hypothesis is that long-term depression (LTD) of parallel fiber-Purkinje cell synapses in the cerebellum embodies part of the neuronal information storage required for associative motor learning. Transgenic mice in which LTD is blocked by Purkinje cell-specific inhibition of protein kinase C (PKC) (L7-PKCI mutants) do indeed show impaired adaptation of their vestibulo-ocular reflex, whereas the dynamics of their eye movement performance are unaffected. However, because L7-PKCI mutants have a persistent multiple climbing fiber innervation at least until 35 d of age and because the baseline discharge of the Purkinje cells in the L7-PKCI mutants is unknown, factors other than a blockage of LTD induction itself may underlie their impaired motor learning. We therefore investigated the spontaneous discharge of Purkinje cells in alert adult L7-PKCI mice as well as their multiple climbing fiber innervation beyond the age of 3 months. We found that the simple spike and complex spike-firing properties (such as mean firing rate, interspike interval, and spike count variability), oscillations, and climbing fiber pause in the L7-PKCI mutants were indistinguishable from those in their wild-type littermates. In addition, we found that multiple climbing fiber innervation does not occur in cerebellar slices obtained from 3- to 6-month-old mutants. These data indicate (1) that neither PKC inhibition nor the subsequent blockage of LTD induction disturbs the spontaneous discharge of Purkinje cells in alert mice, (2) that Purkinje cell-specific inhibition of PKC detains rather than prevents the developmental conversion from multiple to mono-innervation of Purkinje cells by climbing fibers, and (3) that as a consequence the impaired motor learning as observed in older adult L7-PKCI mutants cannot be attributable either to a disturbance in the baseline simple spike and complex spike activities of their Purkinje cells or to a persistent multiple climbing fiber innervation. We conclude that cerebellar LTD is probably one of the major mechanisms underlying motor learning, but that deficits in LTD induction and motor learning as observed in the L7-PKCI mutants may only be reflected in differences of the Purkinje cell signals during and/or directly after training.

Action Potentials↗
PubMed1990

Brain mechanisms underlying motor skill learning in the rat.

Young rats subjected to bilateral brain lesions were subsequently tested for acquisition of eight puzzle-box problems. Lesions to 12 of the 37 brain sites investigated (anterior pretectal area, subthalamus, posterolateral hypothalamus, frontocingulate cortex, anterior thalamus, mediodorsal thalamus, ventromedial thalamus, parafascicular nucleus, mamillary bodies, cerebellum, olfactory bulb, and ventromedial hypothalamus) retarded puzzle-box learning. This study, combined with earlier investigation of 11 additional brain sites, show that 21 of the 48 total brain structures are involved in motor skill learning. These findings suggest that motor skill learning requires the integrity of a nonspecific mechanism and several specific mechanisms, such as vestibular-proprioceptive-kinesthetic discrimination mechanism and probably also response flexibility, visuospatial attentional, visual discrimination and place learning mechanisms.

Animals↗
PubMed2001

An algorithm for modifying neurotransmitter release probability based on pre- and postsynaptic spike timing.

The precise times of occurrence of individual pre- and postsynaptic action potentials are known to play a key role in the modification of synaptic efficacy. Based on stimulation protocols of two synaptically connected neurons, we infer an algorithm that reproduces the experimental data by modifying the probability of vesicle discharge as a function of the relative timing of spikes in the pre- and postsynaptic neurons. The primary feature of this algorithm is an asymmetry with respect to the direction of synaptic modification depending on whether the presynaptic spikes precede or follow the postsynaptic spike. Specifically, if the presynaptic spike occurs up to 50 ms before the postsynaptic spike, the probability of vesicle discharge is upregulated, while the probability of vesicle discharge is downregulated if the presynaptic spike occurs up to 50 ms after the postsynaptic spike. When neurons fire irregularly with Poisson spike trains at constant mean firing rates, the probability of vesicle discharge converges toward a characteristic value determined by the pre- and postsynaptic firing rates. On the other hand, if the mean rates of the Poisson spike trains slowly change with time, our algorithm predicts modifications in the probability of release that generalize Hebbian and Bienenstock-Cooper-Munro rules. We conclude that the proposed spike-based synaptic learning algorithm provides a general framework for regulating neurotransmitter release probability.

Action Potentials↗
PubMed2003

Acquisition and short-term retention of inhaler techniques require intact executive function in elderly subjects.

BACKGROUND: patients with dementia are almost invariably unable to use any form of inhaler. Some elderly patients are unable to learn to use a metered dose inhaler or Turbohaler despite a normal abbreviated mental test score. Studies have shown that in many people this is due to unrecognised cognitive impairment and/or dyspraxia. The executive domains of cognition are particularly important in planning and sequencing; it might be expected therefore that disordered frontal (executive) function could be a predictor of poor inhaler technique in subjects with no overt features of dementia. OBJECTIVE: to explore the relationship between cognitive, and executive, function and the ability to acquire metered dose inhaler and Turbohaler technique in old age. DESIGN: a prospective randomised observational study with blinded evaluation. SUBJECTS: 30 inhaler-naive inpatients (21 female) with a mean age of 85 (range 75-94) and having a normal (8-10) abbreviated mental test score. METHODS: subjects received standardised metered dose inhaler and Turbohaler training and were scored on an analogue scale (for metered dose inhaler) or for competence (Turbohaler) the following day. The Mini-Mental State Examination and EXIT25 (for executive function) were performed by separate observers. RESULTS: significant correlation was found between the metered dose inhaler score and Mini-Mental State Examination (r 0.540, P<0.002) and EXIT25 (r -0.702, P<0.0001). Threshold effects emerged for the metered dose inhaler in that 18/19 with a competent score compared to 2/11 scored as incompetent had a Mini-Mental State Examination of >23 (P<0.01) and 19/19 compared to 0/11 had an EXIT25 of <15 (P<0.01). Similarly, for the Turbohaler 21/21 of the competent subjects had a Mini-Mental State Examination of >23 compared with 3/9 incompetent subjects (P<0.01), with 21/21 competent compared with 0/9 incompetent having an EXIT25 <15 (P<0.01). CONCLUSION: acquisition and short-term retention of metered dose inhaler and Turbohaler techniques is unlikely to be successful in frail elderly people who have an abnormal Mini-Mental State Examination and/or EXIT25 test. The latter test, when abnormal, is probably the superior predictor of inability to learn inhaler techniques.

Aged↗
PubMed1999

Sensitization to apomorphine in pigeons is due to conditioning, subject to generalization but resistant to extinction.

Apomorphine (Apo) administration induces a persistent bout of pecking in pigeons and other birds. Repeated injections of Apo in pigeons lead to sensitization, i.e. the pecking response to a particular dose increases up to a dose-dependent asymptotic level. It is also known that Apo-induced pecking can be classically conditioned to the cage environment where the animals experience the effect of the drug. Here we address the question of whether, and to what extent, the sensitization effect arises as a consequence of a conditioning or of a pharmacological process. An extinction experiment demonstrated that an extinction procedure supposed to be effective in inhibiting the conditioned pecking response was not effective in suppressing the sensitization to Apo, thus casting provisional doubt on the conditioning hypothesis. However, a conditioning experiment demonstrated that the sensitization effect undoubtedly involved an important component of conditioning to an experimental cage environment, but also suggested that there was an additional component possibly not due to learning. A generalization experiment, however, showed that this second component was very probably due to a stimulus generalization effect deriving from conditioning to the home cage, suggesting that learning can account for most, if not all, of the increase in Apo-induced pecking and that an exclusively pharmacological sensitization process plays, at best, a minor role. The apparent contrast between the results of the first experiment, indicating that the sensitization is not affected by inhibitory conditioning, and the results of the last two experiments, suggesting that the sensitization is due to excitatory conditioning, can be resolved by assuming that Apo induces a drug-state-dependent conditioning. These results are related to findings and arguments concerning the sensitization to psychostimulant drugs in mammals.

Animals↗
PubMed1984

Attentional bias between modalities: effect on the internal clock, memory, and decision stages used in animal time discrimination.

Both the presentation of unbalanced stimulus probabilities and the insertion of a predictive cue prior to the signal on each trial apparently induces a strong bias to use a particular stimulus modality in order to select a temporal criterion and response rule. This attentional bias toward one modality is apparently independent of the modality of the stimulus being timed and is strongly influenced by stimulus probabilities or prior warning cues. These techniques may be useful to control trial-by-trial sequential effects that influence a subject's perceptual and response biases when signals from more than one modality are used in duration discrimination tasks. Cross-procedural generality of the effects of attentional bias was observed. An asymmetrical modality effect on the latency to begin timing was observed with both the temporal bisection and the peak procedure. The latency to begin timing light signals, but not the latency to begin timing sound signals, was increased when the signal modality was unexpected. This asymmetrical effect was explained with the assumption that sound signals close the mode switch automatically, but that light signals close the mode switch only if attention is directed to the light. The time required to switch attention is reflected in a reduction of the number of pulses from the pacemaker that enter the accumulator. One positive aspect of this work is the demonstration that procedures similar to those used to study human cognition can be used with animal subjects with similar results. Perhaps these similarities will stimulate animal research on the physiological basis of various cognitive capacities. Animal subjects would be preferred for such physiological experimentation if it were established that they possessed some of the cognitive processes described by investigators of human information processing. One of the negative aspects of this work is that only one combination of modalities was used and variables such as stimulus intensity, stimulus probability, and range of signal durations have not been adequately investigated at present. Future work might test additional combinations of modalities and vary stimulus intensity and stimulus probability within a signal detection theory (SDT) framework to determine the effects of these variables on attentional bias.

Animals↗
PubMed2000

Comparison of the CERAD and CVLT list-learning tasks in Alzheimer's disease.

This investigation examined the relationship of the word list from the CERAD neuropsychological battery to the California Verbal Learning Test (CVLT) in a sample of 138 subjects with Probable Alzheimer's disease (AD). Results revealed modest but statistically significant associations between the two measures on many key variables. Total words learned showed the strongest association, with lower correlations for delayed recall, intrusion errors, and recognition variables. As expected, the CERAD and CVLT assess similar aspects of verbal learning in patients with AD. However, the modest level of many of the correlations suggests that caution should be exercised in applying the same interpretive strategies derived on more comprehensive measures to shorter ones.

Adult↗
PubMed2004

Stress enables synaptic depression in CA1 synapses by acute and chronic morphine: possible mechanisms for corticosterone on opiate addiction.

The hippocampus, being sensitive to stress and glucocorticoids, plays significant roles in certain types of learning and memory. Therefore, the hippocampus is probably involved in the increasing drug use, drug seeking, and relapse caused by stress. We have studied the effect of stress with morphine on synaptic plasticity in the CA1 region of the hippocampus in vivo and on a delayed-escape paradigm of the Morris water maze. Our results reveal that acute stress enables long-term depression (LTD) induction by low-frequency stimulation (LFS) but acute morphine causes synaptic potentiation. Remarkably, exposure to an acute stressor reverses the effect of morphine from synaptic potentiation (approximately 20%) to synaptic depression (approximately 40%), precluding further LTD induction by LFS. The synaptic depression caused by stress with morphine is blocked either by the glucocorticoid receptor antagonist RU38486 or by the NMDA-receptor antagonist D-APV. Chronic morphine attenuates the ability of acute morphine to cause synaptic potentiation, and stress to enable LTD induction, but not the ability of stress in tandem with morphine to cause synaptic depression. Furthermore, corticosterone with morphine during the initial phase of drug use promotes later delayed-escape behavior, as indicated by the morphine-reinforced longer latencies to escape, leading to persistent morphine-seeking after withdrawal. These results suggest that hippocampal synaptic plasticity may play a significant role in the effects of stress or glucocorticoids on opiate addiction.

Animals↗
PubMed2002

Likelihood judgment based on previously observed outcomes: the alternative-outcomes effect in a learning paradigm.

Previous research has demonstrated that intuitive perceptions of certainty regarding a focal outcome are sensitive to variations in how evidence supporting nonfocal alternatives is distributed, even when such variations have no bearing on objective probability. We investigated this alternative-outcomes effect in a learning paradigm in which participants made likelihood judgments on the basis of their memory for past observations of relevant outcomes. In Experiment 1, a manipulation of evidence (observed frequencies) across alternative outcomes influenced not only intuitive certainty estimates about a focal outcome but also numeric subjective probabilities. Experiment 2 ruled out the possibility that these effects were attributable to the influence of information loss on frequency estimations. The findings were consistent with the heuristic comparison account, which suggests that the judged likelihood of a focal outcome will be disproportionately influenced by the strength (frequency) of the strongest alternative outcome.

Humans↗