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Differential acquisition of a "working memory" task by the Roman strains of rats.

Twenty-eight male rats of the Roman strains-fourteen RHA (Roman High Avoidance) and fourteen RLA (Roman Low Avoidance)-were submitted to a positively reinforced task, the delayed reinforced alternation test (DRA), in a T-maze. Performances of RLA rats were significantly better than those of RHA; RLA rats also had higher VTE (vicarious trial and error) and spontaneous alternation (SA) scores. These data confirm the fact that RLA may acquire positively reinforced learning as rapidly, or even more rapidly, than RHA rats, and that the differences in active avoidance behavior between these strains depend more on differential freezing behavior than on learning and memory capacities. Since the delayed reinforced alternation is considered as a working memory test, our results suggest that the Roman strains could be used as a genetic model for the neurobiological study of this form of memory.

Animals↗

Human central auditory plasticity associated with tone sequence learning.

We investigated learning-related changes in amplitude, scalp topography, and source localization of the mismatch negativity (MMN), a neurophysiological response correlated with auditory discrimination ability. Participants (n = 32) underwent two EEG recordings while they watched silent films and ignored auditory stimuli. Stimuli were a standard (probability = 85%) and two deviant (probability = 7.5% each for high [HD] and low [LD]) eight-tone sequences that differed in the frequency of one tone. Between recordings, subjects practiced discriminating the HD or LD from the standard for 6 min. The amplitude of the LD MMN increased significantly across recordings in both groups, whereas the amplitude of the HD MMN did not. The LD was easier to discriminate than was the HD. Thus, practicing either discrimination increased the MMN for the easier discrimination. Learning and changes in the LD MMN amplitude were highly correlated. Source localizations of event-related potentials (ERPs) to all stimuli revealed bilateral sources in superior temporal regions. Compared with the standard ERP, the LD ERP revealed a stronger source in the left superior temporal region in both recordings, whereas the right-sided source became stronger after learning. Consistent with prior studies of auditory plasticity in animals and humans, tone sequence learning induced rapid neurophysiological plasticity in the human central auditory system. The results also suggest that there is asymmetric hemispheric involvement in tone sequence discrimination learning and that discrimination difficulty influences the time course of learning-related neurophysiological changes.

Acoustic Stimulation↗

Contribution of the Roman strains of rats to the elaboration of animal models of memory.

Performances of male rats of the Roman High (RHA)- and Roman Low (RLA)-Avoidance strains were compared along four essential dimensions: working memory, reference memory, spontaneous locomotion and avoidance conditioning. Performances of RLA and RHA rats were significantly different for each dimension. As constantly reported, RHA rats were by far superior to RLA in avoidance conditioning. They had also higher levels of locomotor activity. On the opposite, RLA performed better than RHA in an appetitive working memory task, the delayed reinforced alternation, and were also superior in an appetitive reference memory task, the 5-unit linear maze. These results confirm the fact that RLA rats may acquire positively reinforced learning more rapidly than RHA rats and that the differences in active avoidance behavior between the two strains depend more on differential freezing behavior than on learning or memory capacities. Beyond the problem of the characterization of the Roman strains, these data might give indications on the relationships between behavioral tests widely used in rats, and on their use as memory models.

Animals↗

Comparison of prototype and rote instruction of English names for Chinese visual characters.

This study compared prototype and rote instruction of English names for Chinese visual characters. In the prototype condition, participants were taught the meaning of the prototype that served as the distinctive feature of multicomponent characters. In the rote condition, participants traced the character and wrote its translation. Participants learned more rapidly and maintained more words in the prototype condition.

Adult↗

Learning new words II: Phonotactic probability in verb learning.

Phonotactic probability, a measure of the likelihood of occurrence of a sound sequence, appears to facilitate noun learning (H. L. Storkel, 2001). Nouns and verbs, however, tend to differ in rate of acquisition, indicating that word-learning mechanisms may differ across grammatical class. The purpose of the current study was to examine the effect of phonotactic probability on verb learning. Thirty-four typically developing preschool children participated in a multitrial word-learning task involving nonwords varying in phonotactic probability paired with unfamiliar actions. Multiple measures of word learning were obtained at increasing numbers of exposures. Correct responses were analyzed to examine rate of word learning. Results paralleled those of the previous noun-learning study, with common sound sequences being learned more rapidly than rare sound sequences. The results are interpreted in relation to the effect of distributional regularities on acquisition and the reported discrepancy between noun and verb learning in English.

Analysis of Variance↗

Simple spike and complex spike activity of floccular Purkinje cells during the optokinetic reflex in mice lacking cerebellar long-term depression.

Cerebellar long-term depression (LTD) at parallel fibre-Purkinje cell (P-cell) synapses is thought to embody neuronal information storage for motor learning. Transgenic L7-protein kinase C inhibitor (PKCI) mice in which cerebellar LTD is selectively blocked do indeed exhibit impaired adaptation in the vestibulo-ocular reflex (VOR) while their default oculomotor performance is unaffected. Although supportive, these data do not definitively establish a causal link between memory storage required for motor learning and cerebellar LTD. As the L7-PKCI transgene is probably activated from the early stages of P-cell development, an alternative could be that P-cells develop abnormal signals in L7-PKCI mutants, disturbing mechanisms of motor learning that rely on proper P-cell outputs. To test this alternative hypothesis, we studied simple spike (SS) and complex spike (CS) activity of vertical axis P-cells in the flocculus of L7-PKCI mice and their wild-type littermates during sinusoidal optokinetic stimulation. Both SS and CS discharge dynamics appeared to be very similar in wild-type and transgenic P-cells at all stimulus frequencies (0.05-0.8 Hz). The CS activity of all vertical axis cells increased with contralateral stimulus rotation and lagged ipsiversive eye velocity by 165-180 degrees. The SS modulation was roughly reciprocal to the CS modulation and lagged ipsiversive eye velocity by approximately 15 degrees. The baseline SS and CS discharge characteristics were indistinguishable between the two genotypes. We conclude that the impaired VOR learning in L7-PKCI mutants does not reflect fundamental aberrations of the cerebellar circuitry. The data thus strengthen the evidence that cerebellar LTD is implicated in rapid VOR learning but not in the development of normal default response patterns.

Action Potentials↗

Autism, Asperger's syndrome and the Crick-Mitchison theory of the biological function of REM sleep.

Autism, Asperger's syndrome and other autistic syndromes are developmental brain disorders that cause serious impairments in communication, social interaction, empathy, mood and play. In addition to such deficits, the autistic syndromes involve pathologically high levels of repetitive, stereotypic, ritualistic, compulsive or obsessive behavior, together with extreme resistance to change. According to the Crick-Mitchison theory of the biological function of rapid eye movement sleep, normal brain development in the fetus and infant depends on undisrupted function of a 'reverse learning' mechanism during rapid eye movement sleep. Could abnormalities in this hypothetical reverse learning during rapid eye movement sleep in the fetus explain some aspects of the autistic syndromes? Does the Crick-Mitchison theory suggest if a drug could interfere with rapid eye movement sleep and cross the placental barrier, then that drug might cause developmental brain disorders in the fetus? Should all pregnant women completely avoid caffeine or any agent that might disrupt serotonergic or cholinergic systems?

Autistic Disorder↗

Recovery of spatial learning deficits after decay of electrically induced synaptic enhancement in the hippocampus.

A widespread interest in a long-lasting form of synaptic enhancement in hippocampal circuits has arisen largely because it might reflect the activation of physiological mechanisms that underlie rapid associative learning. As its induction normally requires the 'Hebbian' association of activity on a number of input fibres, we refer to the process as long-term enhancement (LTE) rather than long-term potentiation (LTP), to emphasize its distinction from the ubiquitous, non-associative 'potentiation' phenomena that occur at most synapses, including those exhibiting LTE. Among other evidence that LTE might actually have a role in associative memory is the demonstration that repeated high-frequency stimulation, which saturated the inducible LTE, caused a severe deficit in spatial learning, although it had no effect on well established spatial memory. These results were consistent with a widespread view that information need only temporarily be stored in the hippocampal formation in order for long-term memories to be established in neocortical circuits. In this context, it is important to understand whether the possible underlying synaptic changes are of a permanent character, or are relatively transient. A second question is whether the actual cause of the observed learning deficit is the distruption of the synaptic weight distribution, and/or the limitation of further synaptic change, which presumably results from experimental saturation of the LTE mechanism. Alternatively, the deficit could be a consequence of some unobserved secondary effect of the high-frequency electrical stimulation. Here we demonstrate that learning capacity recovers in about the same time that it takes LTE to decay, which strongly favours the first possibility and supports the idea that LTE-like processes actually underlie associative memory.

Animals↗

Modulation of induced gamma band responses in a perceptual learning task in the human EEG.

Fragmented pictures of an object, which appear meaningless when seen for the first time, can easily be identified after the presentation of an unfragmented version of the same picture. The neuronal mechanism for such a rapid perceptual learning phenomenon is largely unknown. Recently, induced gamma band responses (GBRs) have been discussed as a possible physiological correlate of activity in cell assemblies formed by learning. The present study was designed to investigate the modulation of induced GBRs in a perceptual learning task by using a 128-channel EEG montage. In the first sequence of the experiment, fragmented pictures from the Snodgrass and Vandervart inventory were presented. The fragmentation of the pictures was selected that subjects were unable to identify them. In the second experimental sequence - the perceptual learning sequence - half of the pictures were displayed in their unfragmented version. In the third sequence, all pictures were presented again in the fragmented version. Now, subjects had to rate whether or not they could identify the images. Results showed an increase in spectral gamma power at parietal electrode sites for identified pictures. In addition, neural activity in the gamma band was highly synchronized between posterior electrodes. For pictures not presented in their complete version, we found no such pattern in the third sequence. From our results, we concluded that induced GBRs might represent a signature of synchronized neural activity in a Hebbian cell assembly, activated by the fragmented picture after perceptual learning took place. No difference between identified and unidentified pictures was found in the visual evoked potential in the same time range and in the evoked GBR in the same frequency range as the induced response.

Adult↗

Further analysis of encoding in patients with Huntington's disease.

Arguments favoring the view that derangement of normal encoding processes contributes to the memory defects of patients with Huntington's disease (HD) are supported by the finding that HD patients do not learn highly imageable words more rapidly than they learn words that are difficult to image. But other data indicating that HD patients can use verbal mediators as mnemonic aids for picture recognition question the existence of important and general encoding deficits in HD. In the first of two experiments the influence of imagery on the acquisition and recall of 14-word lists was studied using a free-recall paradigm. Both HD patients and controls learned highly imageable words more quickly and retained them better than low imagery words over a 30-min delay. The impact of imagery on learning was apparent by the first trial. In the second experiment, a modified Brown-Peterson distractor paradigm was used to assess release from proactive interference (PI). It was found that both HD patients and controls exhibited comparable release from PI following a shift in taxonomic categories. The results of both experiments question the importance of encoding deficits in the memorial dysfunctions associated with HD.

Adult↗

Continuing professional development for veterinarians.

Continuing professional development for veterinarians is expected to commence in the year after graduation and continue until retirement. The World Organisation for Animal Health standard for veterinary services is based on principles of an ethical, organisational and technical nature, and a mix of regulation, self-regulation and quality assurance approaches are used. Few jurisdictions have made a minimum requirement of continuing professional development, measured in hours or units, mandatory in 2004, however, there is an increasing expectation of veterinarians to keep a personal record of their continuing professional development activities. Such records might assist in defending complaints about professional misconduct, and provide a basis for planning and monitoring personal professional growth. Continuing professional development can be obtained by a variety of means through structured and unstructured learning activities. The rapid advances in communication technologies and ready access to available electronic databases at the beginning of the 21st century is rapidly changing the way students learn in veterinary schools and how they will acquire continuing professional development during their careers. Universities, governments, professional associations and special interest groups all have roles to play in the delivery of continuing professional development to the veterinary profession and to ensure a structure is in place to monitor improvements in the delivery of quality veterinary services.

Australia↗

A standards-based approach for facilitating discovery of learning objects at the point of care.

Recent concerns about the quality and safety of healthcare practice provide an imperative for discovering and accessing learning resources. The growing ubiquity of the Internet, World Wide Web, and on-line educational content provide opportunity for healthcare practitioners to identify and master learning in a granular and rapid fashion. The e-learning community at large has developed a number of standards to facilitate interoperability of learner competencies, metadata describing on-line content, and packaging and navigation of such content. The overall goal of our project is to enable healthcare professionals to easily and rapidly discover learning content at the point of care. This discovery and access of learning content will be based on healthcare-specific extensions of existing e-learning standards, which are themselves based on other Web standards, such as Web Services.

Curriculum↗

Increased responsiveness of hippocampal pyramidal neurons to nicotine in aged, learning-impaired rats.

The effect of aging upon the responsiveness of hippocampal CA1 pyramidal neurons to nicotine was investigated using electrophysiological techniques in male Fischer 344 rats. Prior to electrophysiological recording, animals were behaviorally tested using the Morris water maze. All 3-6 and 18-21 month rats displayed rapid place learning in this task, while none of the 27-30 month animals learned within the 5-day test period. By contrast, rats of all age groups were able to learn a cue version of the water maze task. Following behavioral testing, the animals were anesthetized with sodium pentobarbital for acute recording. Nicotine was locally applied to electrophysiologically identified CA1 pyramidal neurons using pressure microejection from two-barreled glass microelectrodes. For each neuron, a dose of nicotine was found which elicited a 300-400% increase in basal firing rate. These data were used to construct cumulative dose response curves for populations of neurons tested in 3-6-, 18-21-, and 27-30-month-old animals. An age-related increase in the responsiveness of CA1 pyramidal neurons to locally applied nicotine was observed. The results of this study suggest that an increase in hippocampal CA1 pyramidal cell responsiveness to nicotine could be related to the impaired place learning ability seen with aging.

Action Potentials↗

Nicotinic modulation in an animal model of a form of associative learning impaired in Alzheimer's disease.

Eyeblink classical conditioning is a widely used associative learning paradigm that has striking behavioral and neurobiological parallels between humans and other mammals. Eyeblink conditioning is impaired in older organisms, and patients with Alzheimer's disease (AD) are impaired beyond the normal aging deficit. The cholinergic system is of demonstrated involvement in eyeblink conditioning. Blockade of nicotinic cholinergic receptors with mecamylamine prolonged acquisition of conditioned responses (CRs) in young adult rabbits, and the nicotinic agonist, GTS-21 ameliorated conditioning deficits in older rabbits. Galantamine induces allosteric modulation of nicotinic cholinergic receptors to increase acetylcholine release as well as acting as an acetylcholinesterase inhibitor. Galantamine doses of 0.0, 1.0, 2.0, 3.0, and 4.0 mg/kg were tested in ten daily sessions in 40 retired breeder rabbits (mean age = 29 months) in the 750 ms delay conditioning paradigm. A dose of 3 mg/kg galantamine was effective in improving conditioning in older rabbits, enabling them to achieve learning criterion rapidly and to produce a very high percentage of CRs. Control tests of rabbits in explicitly unpaired conditions demonstrated that non-associative factors could not account for the results. The efficacy of galantamine in a learning paradigm that shows severe impairment in AD indicates that the drug may be effective as a cognition-enhancer in AD.

Age Factors↗

Learning and memory is reflected in the responses of reinforcement-related neurons in the primate basal forebrain.

Certain basal forebrain neurons encode the learned reinforcement value of objects: they respond differentially to visual stimuli that signal availability of fruit juice (positively reinforcing) or saline (negatively reinforcing) obtained by lick responses in visual discrimination tasks. In this report we describe the rapid, learning-related changes in the responses of these neurons during the acquisition and reversal of the reinforcement contingency of a visual discrimination reversal task. The same neurons also responded differentially to novel and familiar stimuli in 2 recognition memory tasks, in which monkeys applied the learned rule that lick responses to novel stimuli elicited saline and responses to familiar stimuli elicited juice. These differential responses to novel and familiar stimuli thus reflected the reinforcement value of the stimuli. A single presentation of a novel or a familiar stimulus was sufficient to elicit a differential response which was maintained even when the stimulus had not been seen recently. The maintenance of the differential response indicates that these neurons are influenced by a durable memory for the stimuli, estimated to be 30 trials on average. These differential neurons were recorded in the substantia innominata, the diagonal band of Broca, and a periventricular region of the basal forebrain. The responses of the reinforcement-related neurons in these 3 regions were similar in most respects. These results support the conclusion that basal forebrain neurons respond to sensory stimuli that, through learning of different contingencies, signal the availability of reinforcement. We suggest that the properties of learning and memory reflected in these neuronal responses are due to afferent pathways from ventromedial regions of the prefrontal and temporal cortices and the amygdala, and that the responses of these neurons provide an enabling mechanism that facilitates the operation of diverse cortical regions in which specific sensory, motor, or mnemonic functions take place.

Animals↗

Effects of modeling and corrected practice on generative language learning of preschool children.

A simultaneous treatments design was used to compare the effects of modeling and corrected practice on generative language acquisition of six preschool children. New syntactic forms used to describe agent-action and agent-action-object stimuli were taught concurrently. All six children learned both new syntactic forms. However, generative language learning was accomplished more efficiently with corrected practice, irrespective of the number of words or the linguistic complexity of utterance forms. When modeling was not effective initially, instructing two children to start talking like the model resulted in rapid observational learning. It is suggested that descriptive researchers may have prematurely discounted the possible role of corrected practice in the enhancement of language learning. This analog study indicates that corrected practice should provide a more efficient approach for establishing generalized syntactic responding, at least initially, in language intervention programs.

Child Language↗

Online tuning of fuzzy inference systems using dynamic fuzzy Q-learning.

This paper presents a dynamic fuzzy Q-learning (DFQL) method that is capable of tuning fuzzy inference systems (FIS) online. A novel online self-organizing learning algorithm is developed so that structure and parameters identification are accomplished automatically and simultaneously based only on Q-learning. Self-organizing fuzzy inference is introduced to calculate actions and Q-functions so as to enable us to deal with continuous-valued states and actions. Fuzzy rules provide a natural mean of incorporating the bias components for rapid reinforcement learning. Experimental results and comparative studies with the fuzzy Q-learning (FQL) and continuous-action Q-learning in the wall-following task of mobile robots demonstrate that the proposed DFQL method is superior.

Algorithms↗

Learning arm kinematics and dynamics.

In this review I have discussed how the form of representation used in internal models of the motor apparatus affects how and what a system can learn. Tabular models and structured models have benefits and drawbacks. Structured models incorporate knowledge of the structure of the controlled motor apparatus. If that knowledge is correct, or close to the actual system structure, the structured models will support global generalization and rapid, efficient learning. Tabular models can play an important role in learning to control systems when either the system structure is not known or only known approximately. Tabular models are general and flexible. Techniques for combining these different representations to attain the benefits of both are currently under investigation. In the control of multijoint systems such as the human arm, internal models of the motor apparatus are necessary to interpret performance errors. In the study of movements restricted to one joint, the problem of interpreting performance errors is greatly simplified and often overlooked, as performance errors can usually be related to command corrections by a single gain. When multijoint movements of the same motor systems are examined, however, the complex nature of the control and coordination problems faced by the nervous system become evident, as well as the sophistication of the brain's solutions to these problems. Recent progress in the understanding of adaptive control of eye movements provides a good example of this (Berthoz & Melvill-Jones 1985). Experimental studies of the psychophysics of motor learning can play an important role in bridging the gap between computational theories of how abstract motor systems might learn and physiological exploration of how actual nervous systems implement learning. Quantitative analyses of the patterns of motor learning of biological systems may help distinguish alternative hypotheses about the representations used for motor control and learning. What a system can and cannot learn, the amount of generalization, and the rate of learning give clues as to the underlying performance architecture. It is also important to know the actual performance level of the motor system (Loeb 1983). Different proposed control strategies will be able to attain different performance levels, and the use of simplifying control strategies may be evident in the control and learning performance of motor systems.

Arm↗