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PubMed1995

Modulation of learning processes by ionotropic glutamate receptor ligands.

A great body of evidence has been provided for the role of N-methyl-d-aspartate (NMDA) receptors in learning processes, since the pioneering work of Morris et al. (1986) showing impairment of water maze learning and long-term potentiation (LTP) during i.c.v. infusion of the NMDA receptor antagonst 2-amino-5-phosphonovaleric acid (AP5). The existing literature, based on pharmacological studies, suggests the importance of NMDA receptors for the acquisition and/or the initial phase of long-term memory consolidation in many, but not all, learning paradigms. Data on short-term memory are inconsistent, probably due to difficulties in separation of learning deficits from performance. Although it is generally accepted that NMDA receptor antagonists impair learning, more recent data suggest that, under certain conditions, the opposite effect, enhancement of learning, can be obtained. The role of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors in learning, although accepted in LTP, is less well documented. It has been suggested that positive modulation of these receptors could result in cognitive enhancement that might find therapeutic application. The present paper reviews the literature dealing with these issues and discusses possible consequences for the therapy of dementia.

Journal Article↗
PubMed2005

Amyloid precursor protein expression in the rat hippocampal dentate gyrus modulates during memory consolidation.

Despite advances in our understanding of the basic biology of amyloid precursor protein (APP), the normal physiological function(s) of APP in learning and memory remains unclear. Here we show increased APP degradation in the hippocampus to be associated with the consolidation of a passive avoidance response. Neurone-specific APP695 expression became transiently reduced 2-4 h post-training through association with endosomal adaptin proteins and enhanced internalization. By contrast, internalization of glial-associated APP containing a Kunitz protease inhibitor-like domain (APP-KPI) was dependent on the low-density lipoprotein receptor-related protein (LRP). In addition, LRP expression and association with apolipoprotein E increased in the 2-4 h post-training period. The LRP antagonist receptor-associated protein prevented the APP-KPI internalization and LRP-apolipoprotein E association and this resulted in amnesia. Degradation of APP695 and APP-KPI did not appear to be related to alpha-secretase activity, as no learning-associated increase of secreted APP was observed in the CSF. Moreover, as internalization of APP isoforms was observed only in dentate gyrus, it probably relates to the learning-associated restructuring of the perforant path terminals. Memory-associated APP processing in both neuronal and glial compartments points to a role for glial unsheathing of synaptic connections, an event required for the synaptic restructuring that accompanies memory consolidation. These observations may have a direct relevance to understanding the pathophysiology of Alzheimer's disease as beta/gamma-secretase-derived beta-amyloid is formed following internalization of cell surface APP into the endosomal compartment.

Adaptor Protein Complex Subunits↗
PubMed2006

From recurrent choice to skill learning: a reinforcement-learning model.

The authors propose a reinforcement-learning mechanism as a model for recurrent choice and extend it to account for skill learning. The model was inspired by recent research in neurophysiological studies of the basal ganglia and provides an integrated explanation of recurrent choice behavior and skill learning. The behavior includes effects of differential probabilities, magnitudes, variabilities, and delay of reinforcement. The model can also produce the violation of independence, preference reversals, and the goal gradient of reinforcement in maze learning. An experiment was conducted to study learning of action sequences in a multistep task. The fit of the model to the data demonstrated its ability to account for complex skill learning. The advantages of incorporating the mechanism into a larger cognitive architecture are discussed.

Animals↗
PubMed2003

Conditionals and conditional probability.

The authors report 3 experiments in which participants were invited to judge the probability of statements of the form if p then q given frequency information about the cases pq, p not q, not pq, and not p not q (where not = not). Three hypotheses were compared: (a) that people equate the probability with that of the material conditional, 1 - P(p not q); (b) that people assign the conditional probability, P(q/p); and (c) that people assign the conjunctive probability P(pq). The experimental evidence allowed rejection of the 1st hypothesis but provided some support for the 2nd and 3rd hypotheses. Individual difference analyses showed that half of the participants used conditional probability and that most of the remaining participants used conjunctive probability as the basis of their judgments.

Color Perception↗
PubMed1999

Apraxia and motor-skill acquisition in Alzheimer's disease are dissociable.

Many patients with Alzheimer's disease (AD) are apraxic and the apraxia has been posited to be related to a loss of movement representations. Whereas patients with Alzheimer's disease have been reported to demonstrate normal motor learning on a rotor pursuit skill acquisition task, it is unknown whether AD subjects who are apraxic demonstrate normal skill-learning. We tested subjects with probable AD and normal controls on a rotor pursuit task. We also tested the AD subjects for ideomotor apraxia. Subjects with AD who were apraxic had normal motor learning. In addition, praxis score did not correlate with performance on the skill-acquisition task. The results suggest that ideomotor praxis and motor learning are at least partly dissociable.

Aged↗
PubMed2005

Effects of errorless and errorful face-name associative learning in moderate to severe dementia.

BACKGROUND AND AIMS: The prevention of errors during learning has been found to be effective in overcoming memory problems in patients with amnesia compared with errorful or trial-and-error learning, possibly as a result of intact implicit memory function. Although errorless learning is a clinically promising technique used in cognitive training settings, to date only a few studies have examined errorless learning in patients with dementia. METHODS: The current study examined errorless and errorful learning using a face-name associative memory task in a group of moderate to severe dementia patients suffering from probable Alzheimer's disease (MMSE < or = 22; n = 10) using a fully counterbalanced within-subject design. RESULTS: Errorless learning had a significantly beneficial effect after two consecutive learning trials (p = 0.01). However, after an unfilled delay of 10 minutes, no significant differences in memory performance were found between errorless and errorful learning. Furthermore, current effects were much smaller compared with previous findings in healthy adults and early-stage dementia patients. CONCLUSIONS: Although errorful learning resulted in better performance in a face-name associative memory task in patients with dementia, this effect was only short-lived. Thus, the beneficial effects of errorless learning are probably not due to intact implicit memory function, but may also be subserved by explicit memory, a memory system that is typically impaired in dementia. Also, the clinical applicability of errorless learning in teaching patients with moderate to severe dementia face-name associations is limited.

Aged↗
PubMed2003

Musical skill in dementia: a violinist presumed to have Alzheimer's disease learns to play a new song.

Previous studies have described patients with possible or probable Alzheimer's disease (AD) who continued to play familiar songs skillfully, despite their dementias. There are no reports about patients with dementia who successfully learned to play new songs, and two papers describe failures of patients with AD to learn to play a new song although they continued to play familiar songs competently. In the present paper we describe a moderately demented patient (SL) with probable AD who learned to play a song (Cossackaya!) on the violin that was published after the apparent onset of his dementia. He showed modest retention of the song at delays of 0 and 10 minutes. This contrasts with his profound disturbance in both recall and recognition on other anterograde memory tests (word lists, stories, figures, environmental sounds, sounds of musical instruments), and marked impairment on measures of remote memory (famous faces, autobiographical memory). SL showed milder deficits in confrontation naming, verbal fluency and attention, but no dyspraxia or aphasic comprehension deficits. Except for the Block Design test, his visuospatial skills were intact. SL's learning of the new song in the absence of any evidence of episodic memory is reminiscent of patients with temporal lobe amnesia who show better memory for song melody than for lyrics or verse, although his retention was not as good.

Aged↗
PubMed1962

Elementary thinking and the classification of behavior.

A theory of thinking is presented which attributes the human brain's outstanding efficiency and versatility in problem solving and learning to two memory functions. The brain's efficiency is considered to be largely a function of the capacity to remember previous operations involved in finding answers to questions. Man's outstanding versatility in problem solving is basically attributed to memory which can activate, maintain, and terminate activities independent of, or only indirectly related to, environmental or physiologic regulatory factors. Within-brain activity patterns which have unidirectionally alterable probabilities of appearance allow for adaptation (learning). The fact that the probability of appearance of nervous system activity can be altered to approach zero or unity allows nervous system units to act as their own timing controls during answer finding; the fact that units are combined into pathways allows for propagation of addressed messages at rates of the same order of magnitude as those of the timing controls.

Behavior↗
PubMed2005

Effector-dependent and response location learning of probabilistic sequences in serial reaction time tasks.

We investigated the contributions of the sequences of effectors and response locations to probabilistic sequence learning in the serial reaction time task by means of bimanual transfer. Participants, trained with the dominant hand, were either required to maintain responding with the dominant hand after transfer or to switch to the nondominant hand. For both groups, half of the participants were transferred to the originally trained sequence, whereas the other half was transferred to a mirror-ordered sequence. This way, the sequence of effectors varied independently of the sequence of response locations. Sequence learning was assessed with probabilistic sequences, composed of either first-order or second-order probabilities. Transfer of sequence knowledge to the nondominant hand was equally good for the originally trained sequence as for the mirrored sequence. This suggests that probabilistic sequence learning can be based on either the sequence of effectors or response locations. However, when participants responded with the dominant hand to a mirrored sequence, transfer performance was disturbed. This indicates that changing both the sequences of effectors and response locations has a disruptive effect on the learning performance.

Adult↗
PubMed1999

The electronic learning zone in health informatics.

This paper outlines developments in health informatics education arising from the rapid development of the Internet and the growing importance of lifelong learning. The drivers for change in educational delivery are examined and examples of related uses of the Internet are given. The development of the Electronic Learning Zone at the University of Surrey is described and the paper concludes with the probable future extensions to support lifelong learning.

Computer-Assisted Instruction↗
PubMed2002

Toward a unified theory of decision criterion learning in perceptual categorization.

Optimal decision criterion placement maximizes expected reward and requires sensitivity to the category base rates (prior probabilities) and payoffs (costs and benefits of incorrect and correct responding). When base rates are unequal, human decision criterion is nearly optimal, but when payoffs are unequal, suboptimal decision criterion placement is observed, even when the optimal decision criterion is identical in both cases. A series of studies are reviewed that examine the generality of this finding, and a unified theory of decision criterion learning is described (Maddox & Dodd, 2001). The theory assumes that two critical mechanisms operate in decision criterion learning. One mechanism involves competition between reward and accuracy maximization: The observer attempts to maximize reward, as instructed, but also places some importance on accuracy maximization. The second mechanism involves a flat-maxima hypothesis that assumes that the observer's estimate of the reward-maximizing decision criterion is determined from the steepness of the objective reward function that relates expected reward to decision criterion placement. Experiments used to develop and test the theory require each observer to complete a large number of trials and to participate in all conditions of the experiment. This provides maximal control over the reinforcement history of the observer and allows a focus on individual behavioral profiles. The theory is applied to decision criterion learning problems that examine category discriminability, payoff matrix multiplication and addition effects, the optimal classifier's independence assumption, and different types of trial-by-trial feedback. In every case the theory provides a good account of the data, and, most important, provides useful insights into the psychological processes involved in decision criterion learning.

Animals↗
PubMed2003

Recruitment, retention, and compliance results from a probability study of children's environmental health in economically disadvantaged neighborhoods.

The School Health Initiative: Environment, Learning, and Disease (SHIELD) study used a probability sample of children (second through fifth grades) from two low-income and racially mixed neighborhoods of Minneapolis, Minnesota, to assess childhood environmental health. Children were eligible to participate in SHIELD regardless of whether they or their families spoke a foreign language, their household had a telephone, or they were enrolled in a special education program. The overall enrollment rate in year 1 was 57%, with a substantial disparity between children from English-speaking (42%) versus non-English-speaking (71%) families. At the end of year 1, 85% were retained in the study. A relatively high percentage of children provided the two requested blood (82%) and urine (86%) samples in year 1, and 90% provided a valid spirometry sample. Eighty-two percent provided both requested volatile organic chemical badge samples, and both time-activity logs were obtained from 66%. However, only 32% provided both peak flow measurements. All percentages increased for those participating in the second year of the study. Results indicate that a school-based research design makes it feasible and practical to conduct probability-based assessments of children's environmental health in economically disadvantaged and ethnically diverse neighborhoods. There is an ongoing need, however, to improve understanding of the cultural, economic, psychologic, and social determinants of study participation among this population.

Child↗
PubMed2006

The importance of decision making in causal learning from interventions.

Recent research has focused on how interventions benefit causal learning. This research suggests that the main benefit of interventions is in the temporal and conditional probability information that interventions provide a learner. But when one generates interventions, one must also decide what interventions to generate. In three experiments, we investigated the importance of these decision demands to causal learning. Experiment 1 demonstrated that learners were better at learning causal models when they observed intervention data that they had generated, as opposed to observing data generated by another learner. Experiment 2 demonstrated the same effect between self-generated interventions and interventions learners were forced to make. Experiment 3 demonstrated that when learners observed a sequence of interventions such that the decision-making process that generated those interventions was more readily available, learning was less impaired. These data suggest that decision making may be an important part of causal learning from interventions.

Attention↗
PubMed1990

Duration of signals for intertrial reinforcement and nonreinforcement in random control procedures.

In the random control procedure, responding to a conditioned stimulus (target CS) is prevented when the probability of unsignaled, unconditioned stimuli (USs) in the intertrial interval (ITI) is equal to the probability of the US in the presence of the target CS. Three experiments used an autoshaping procedure with White Carneaux pigeons to examine the effects of the temporal duration of signals for the ITI USs (cover CSs) and for concomitant periods of nonreinforcement. In Experiment 1, a short duration cover, but not a long duration cover, resulted in responding to the target CS. In Experiment 2, an explicit CS- cue during periods of nonreinforcement did not affect target acquisition. In Experiment 3, a long CS-, but not a short cover CS, was a sufficient condition for the acquisition of responding to the target CS. These results imply that the acquisition of responding to a target CS requires a discriminable period of nonreinforcement that is long relative to the target CS duration.

Animals↗
PubMed1999

The recognition memory of imprinting: biochemistry and electrophysiology.

A restricted part of the intermediate and medial part of the hyperstriatum ventrale (IMHV) of the domestic chick forebrain is pivotal to the learning process of imprinting and is probably the site at which information about an imprinting stimulus is stored. A range of learning-related changes occur in the IMHV between 1 and 24 h after training. The earliest change described is in Fos-like immunoreactivity. There follow changes in phosphorylation of the protein kinase C substrate MARCKS, morphological changes in axospinous synapses, an increase in NMDA receptor number and increases in amounts of the major isoforms of the neural cell adhesion molecule and clathrin heavy chain. All but the change in Fos-immunopositivity occurs in the left, but not the right, IMHV. Insufficient nitric oxide synthase is available in the IMHV to support the hypothesis that nitric oxide is a retrograde messenger contributing to the effect on Fos-like immunoreactivity. In chicks anaesthetised approximately 24 h after imprinting training, the spontaneous mean neuronal firing rate is related to a preference score (a measure of learning). In unanaesthetised chicks 24 h after training, the responsiveness of some IMHV neurons is biassed specifically towards the imprinting stimulus.The responses of other neurons in the IMHV generalise across some features of the training stimulus, such as form or colour. Some neurons in the IMHV of unanaesthetised chicks are responsive to the distance of an imprinting stimulus from the chick; distance-sensitive neurons can be distinguished from distance-insensitive neurones by the action potential shape.

Animals↗
PubMed2006

Locally Bayesian learning with applications to retrospective revaluation and highlighting.

A scheme is described for locally Bayesian parameter updating in models structured as successions of component functions. The essential idea is to back-propagate the target data to interior modules, such that an interior component's target is the input to the next component that maximizes the probability of the next component's target. Each layer then does locally Bayesian learning. The approach assumes online trial-by-trial learning. The resulting parameter updating is not globally Bayesian but can better capture human behavior. The approach is implemented for an associative learning model that first maps inputs to attentionally filtered inputs and then maps attentionally filtered inputs to outputs. The Bayesian updating allows the associative model to exhibit retrospective revaluation effects such as backward blocking and unovershadowing, which have been challenging for associative learning models. The back-propagation of target values to attention allows the model to show trial-order effects, including highlighting and differences in magnitude of forward and backward blocking, which have been challenging for Bayesian learning models.

Attention↗
PubMedDate not supplied

[Reactions of hippocampal neurons at different stages of rat avoidance conditioning].

The electrophysiological responses of neurons were compared in hippocampal slices from rats acquired and not acquired the passive avoidance reaction after the same conditioning procedure. Associative conditioning was accompanied by a gradual increase in the amplitude of the population spike evoked in CA1 area by stimulation of Schaffer collaterals. However, after reaching the learning criterion, the population spike significantly decreased. These phenomena were observed only at low (not maximal) intensities of test stimuli. After reaching the learning criterion, the paired-pulse facilitation was significantly higher in the slices prepared from the well-learned animals as compared with other groups (those having not reached the learning criterion, passive and active control). The obtained evidence validates the hypothesis that the observed intergroup differences stem from modifications of synaptic efficacy and suggests that after behavioral acquisition, plasticity induced by associative learning was substituted by other mechanisms probably related with declarative memory formation.

Animals↗